Note: Descriptions are shown in the official language in which they were submitted.
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HEAT CAPTURE, TRANSFER AND RELEASE FOR INDUSTRIAL APPLICATIONS
[0001] This invention relates to the field of thermal energy capture,
transfer, and
release in applications, such as thermal treatment for enhanced oil recovery
(EOR), heating
underground geological deposits, recovering heat from geothermal sources, and
efficiently
transferring heat in multiple industrial applications. In particular,
embodiments of the invention
relate to systems and methods of capturing, transferring, and releasing
thermal energy from
intermittent sources (such as metallurgical operations), continuous sources at
high temperature
(such as chemical and petro-chemical operations) and continuous sources at low
temperature
(such as waste heat sources). A key feature of the invention is the ability to
transfer heat over
short or long distances with minimal heat and temperature losses. The
invention also includes
methods of manufacturing devices for the capture, transfer and release of heat
energy, and
methods to install such devices in numerous industrial applications.
BACKGROUND
[0002] In most industrial situations, heat capture involves the transfer
of such energy
from hot gases, liquids, or solids into other media that either conduct heat
away via thermal
conductivity, as is the case of heat exchangers. phase-change involving
evaporation or melting,
as is the case of quenching reactions, or by convection or radiation. However,
in many industrial
systems heat is mainly dissipated rather than captured by conduction,
convection or radiation. For
example, melting and quenching operations, such as the quenching of hot
metallurgical coke with
water, seldom capture the radiation or the steam produced, so the heat is
dissipated but not
captured. Most heat capture operations in industry rely on the thermal
conductivity of a metal or
other material that encapsulates the heat producing medium. This metal or
other material
subsequently transfers the heat away from its source. Therefore, a critical
parameter in heat
capture is the thermal barrier presented by the encapsulating material. This
thermal barrier is
also a critical parameter in the eventual release of heat.
[0003] When the heat is captured, methods of thermal transfer over
distance normally
rely on either insulated steam pipelines or the transfer of heat via thermal
fluids which may
include oil-based fluids, such as DowTherm , eutectic mixtures such as molten
salts, molten
metals such as Na, or Pb, or Sn (these may be appropriate for metallurgical
applications), or
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molten alloys. Steam is usually preferred in most industrial applications
because it provides a
considerable amount of heat upon condensation, it is often the low cost option
and is easily
pumped over some distance. However, heat losses in moving steam are also quite
significant in
spite of insulation, and so the distance over which steam can be economically
transferred is
necessarily limited. The same is true of thermal fluids with the aggravating
feature of the
additional weight and costs involved. In the case of molten salts, the entire
pipeline would
require replacement if the salt were allowed to "freeze" in place, a problem
that has often
occurred.
[0004] In addition to the above limitations and parameters, some
industrial
applications present unique problems to the capture, transfer, and release of
heat, and deserve
further discussion.
Heat transfer in Enhanced Oil Recovery
[0005] In conventional oil production, oil is recovered from oil bearing
salt domes by
drilling. Since the typical oil formation is under pressure, initial
production is facilitated by the
flow of oil to the surface under pressure. Over time, such natural flow
decreases as the pressure
declines, and production relies on enhanced oil recovery methods. These
methods may include
pressurization by injecting CO2, water flooding, or heating with steam. Steam
injection has
become popular, because (a) the increase in temperature caused by the steam
decreases the fluid
viscosity of the oil, (b) the water that condenses underground also displaces
the oil while
increasing underground pressure, and (c) the dual phase flow may reduce
overall flow viscosity.
[0006] As conventional oil deposits are exhausted, oil production is
increasingly
relying on oil shales and similar formations that are generally less porous
and more difficult to
access. Such oil sources are generally subjected to hydraulic fracturing,
otherwise known as
"fracking," where water pulses at great pressure are used to fracture
underground rocks so as to
enhance porosity, thus allowing the flow of hydrocarbons (natural gas or oil)
to the surface. Over
time, a similar decrease in the flow of hydrocarbons occurs as underground
pressure declines
with production, and similar EOR methods are employed: water. CO2, or steam
injection. All
such methods are energy intensive and costly. There is a need for EOR methods
that are energy
efficient and that do not require vast amounts of water for either injection
or steam production.
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Heat transfer from Geothermal fields
[0007] Unlike the case of enhanced oil recovery where the problem is to
get heat
down to the oil below the surface, geothermal fields have thermal energy
already below the
surface, and therefore heat can flow from the bottom to the top of a heat pipe
or thermosyphon,
while the working fluid from the top to the bottom either by gravity, through
a wick, or by both.
Thus, the key impediment to the use of heat pipes in geothermal applications
is the distance of
the heat transfer, that is, the practical length needed for the heat pipe or
thermosyphon.
Heat transfer in Industrial Applications
[0008] Most industrial applications involve operating plants where
facilities are
distributed in a fairly level field sometimes covering several acres and
numerous production
units. Thermal energy in such facilities is normally available where
exothermic reactions take
place, in boiler houses, furnaces, and the like, whereas thermal energy may be
required at some
distance from those facilities. Thus, heat transfer at industrial plants
primarily involves horizontal
transfer over hundreds or a few thousands of feet, but normally does not
entail transfer over a
significant vertical distance.
[0009] Heat pipes, with their outstanding heat flux rates due to
internal mass transfer
of vapor, are well suited to horizontal heat transfer because there is no
significant limitation of
capillary action over distance. Thus, the main practical limitation for this
type of application
stems from the length of commercially available heat pipes.
SUMMARY
[0010] Embodiments of the present invention provide novel means for
capturing,
transferring, and subsequently releasing heat that can be applied to
industrial applications, such
as thermal treatment for enhanced oil recovery (EOR), heating underground
geological deposits,
recovering heat from geothermal sources, controlling temperature in chemical
processes,
capturing and reusing waste heat in plants and factories, and efficiently
transferring heat in a
wide variety of other industrial applications. In particular, embodiments of
the invention relate
to systems and methods of capturing, transferring, and releasing thermal
energy from intermittent
sources (such as metallurgical operations), from continuous sources at high
temperature (such as
chemical and petro-chemical operations), and from continuous sources at low
temperature (such
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as waste heat sources). A key feature of the invention is the ability to
transfer heat over short or
long distances with minimal heat and temperature losses. The invention
includes methods of
manufacturing devices for the capture, transfer and release of heat energy,
and methods to install
such devices in numerous industrial applications. The invention allows for the
rapid transfer of
heat at temperatures in the range of -40 C to 1300 C, or more, from a
variety of heat sources,
and the subsequent release of such heat at variable or constant temperature
for a long period of
time. The system includes a novel heat pipe that is thermally insulated over
most of its length. In
some embodiments, the low end of the temperature range can be 0, 50, 100, 150,
200, and 250
degrees. The upper end of the temperature range can be 1500 or more, 1400,
1300, 1200, 1100,
1000, 900, 800, 700, 600, 500, 400, and 300 degrees. In embodiments of the
system, the
dimensions of the heat pipe, the type of thermal insulation, the fabrication
method, and its
placement in the field are determined by the conditions and characteristics of
each industrial
application, by the demand of heat transfer in terms of heat release, and by
the type of thermal
energy available.
[0011] Some embodiments of the invention provide a heat management
system that
can include a plurality of heat transfer devices that can include, for
example, conventional heat
pipes, advanced heat pipes, thermosyphons, heat spreaders, pulsating or loop
heat pipes, steam
pipes, and the like, assembled into an entity providing continuous thermal
communication,
adapted to capture, transfer, and release heat at temperatures in the range of
-40 C to 1,300 C at
a distances of from 0.1 m to 14 km, with a temperature loss from capture to
release between 0%
and 40% of a temperature at a source of the heat to be transferred, wherein
the heat thus can be
transferred from one or more heat sources, and wherein the heat transfer
devices can capture or
provide heat for at least one application. In some embodiments of the
invention, the distance can
be from 0.3m, lm, 3m, 10m, 30m, 100m, 300m, 500m, and lkm to 2km, 3km, 4km,
5km, 6km,
7km, 8km, 9km, 10km, 11km, 12km, 13km, 14km, or more. Likewise, in some
embodiments of
the invention, the temperature loss or heat loss can be 0%, 1%, 2%, 3%, 4%,
5%, 6%, 7%, 8%,
and 9% at a low end and 12%, 15%, 20%, 25%, 30%, 35%, or 40%, or more.
Acceptable
temperature loss can depend upon the circumstances of the particular use of
the system. In some
situations, a very low heat loss is particularly advantageous and may be
required in order for a
particular application to be cost-competitive. In other situations, where the
competing
technologies are ineffective or inoperable, a larger amount of heat loss or
temperature loss can be
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acceptable and can be highly competitive with any alternative available.
Accordingly, the desired
or market-required degree of minimization of heat loss can be relative to
competitive
alternatives.
[0012] In other embodiments, the heat management system can include one
or more
heat transfer devices that can include, for example, conventional heat pipes,
advanced heat pipes,
thermosyphons, heat spreaders, pulsating or loop heat pipes, steam pipes, or
the like, and can also
include a combination of such heat transfer devices, assembled into an entity
that can provide
continuous thermal communication adapted to capture, transfer, and release
heat at temperatures
in the range of -40 C to 1,300 C at a distance of from 500 m to 14 km with a
temperature loss
from capture to release between 0% and 40% of a temperature at a source of the
heat to be
transferred, wherein the heat thus can be transported from one or more heat
sources, and wherein
the heat transfer devices can capture or provide heat for at least one
application.
[0013] In other embodiments, the heat transfer devices of the system can
have one or
more wicks. In some embodiments, the heat transfer devices can have no wicks.
In some
embodiments, the heat transfer devices can include an encapsulating material
manufactured from,
for example, steel, copper and its alloys, titanium and its alloys, aluminum
and its alloys, nickel
and chromium alloys, wound metal foils, wire screens, scaffolds, and the like,
or any
combination thereof. In other embodiments, the heat transfer device can
include different metals
and alloys that can include varying thermal conductivities.
[0014] In other embodiments, the heat transfer devices of the system can
include
multiple sections such as, for example, evaporators, heat transfer sections,
and condensers, or the
like. In some embodiments, the sections can include a wick characteristic such
as no wicks, full
wicks, partial wicks, and the like, or any combination thereof.
[0015] In further embodiments, the application of the system can
include, for
example, power plants, geothermal energy production, enhanced oil recovery,
gas recompression,
water desalination, metallurgical processing, chemical and petrochemical
operations and
production, pulp and paper industries, plastic and rubber operations,
refractory industry,
glassmaking operations, mining operations, plywood and oriented strand board
manufacturing,
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fermentation, fertilizer production, industrial gas production, military
applications, solar energy
production, rubber manufacturing, oil refineries, and the like.
[0016] In additional embodiments, the encapsulating material of the heat
transfer
devices can include, for example, a metal, plastic, or ceramic composition, or
a composition
combining such components, that can be non-reactive with respect to the
variety of heat sources,
non-reactive with respect to a heat transfer medium, and non-reactive with
respect to the heat
source.
[0017] In other embodiments, different individual wicked heat transfer
devices can be
joined so a joined wick structure can exist, having continuity compatible with
capillary action
along the length, the continuity can permit thermal communication of internal
working materials
throughout the length, and the internal working materials include, for
example, fluids, solids that
sublimate, materials having multiple chemical hydration levels, and the like,
as well as any
combination thereof.
[0018] In other embodiments, the wick structure can include multiple
layers having
different porosities. In further embodiments, the wick structure can include
an internal wick
structure that can include an axial wick. In other embodiments, the wick
structure can include
materials such as,for example, sintered metals, metal screens, grooves,
oxides, borates, solids
that sublimate, materials with different chemical hydration levels, nano-
particles, nanopores,
nanotubes, and the like.
[0019] In additional embodiments, different materials can be used at
different
positions along the length, and the materials can be selected to optimize heat
capture and release,
while minimizing heat loss.
[0020] In other embodiments, the wick can be formed, for example, by
spraying,
painting, baking, PVD, CVD, pyrolysis of organic compounds, or the like. In
some
embodiments, the wick can be formed by thermally decomposing a slurry of metal
particles in a
liquid metal precursor and/or by similar processes.
[0021] In some embodiments, the encapsulating tube can include a wound
strip of foil
or the like; the foil can be thin in some embodiments.
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[0022] In additional embodiments, the wound strip structure can be pre-
coated with
wick material before being formed into tubular assemblies around, for example,
metal scaffolds
or the like that can include, for example, mesh screens.
[0023] In some embodiments, any gaps in the wound tube can be sealed by
a separate
wound strip or the like.
[0024] In some embodiments, the amount of working material can be in
excess of
what is needed to saturate the internal wick structure.
[0025] In some embodiments, the working material in the heat transfer
devices can
have a phase change temperature in the range of -40 C and 1,300 C, or more.
[0026] In some embodiments, the heat transfer device can include at
least one valve
proximate to at least one end in order to control and maintain partial vacuum.
[0027] In some embodiments, vertical heat transfer devices of up to 14km
in length
can be installed in a manner to prevent the physical degradation or breakage
of the heat transfer
devices. In such embodiments, the weight of the heat transfer device is
neutralized by, for
example, at least one buoyant balloon, at least one helicopter, a combination
thereof, or the like.
[0028] In various embodiments, the heat transfer devices can be
installed using at
least one installation aid such as a crane, a helicopter, a balloon, a wheel,
an oil rig, a tower, or
the like. In some embodiments, heat transfer devices of, for example. 3-7 Km
in length can be
installed without physical degradation or breakage of such heat transfer
devices, and the heat
transfer device can be wound around a wheel of, for example, 100-500 feet in
diameter that
minimizes the curvature of the heat transfer device. In some embodiments, the
heat transfer
devices can be insulated.
[0029] In some embodiments, pulsating heat pipes can be made by
encapsulating a
thin metal or alloy layer in, for example, a strong metal screen or the like,
to resist pressure
pulses.
[0030] Some embodiments of the invention can include a method of heat
capture,
transfer and release using a heat management system.
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[0031] Some embodiments include methods for manufacturing a heat
management
system that can include the steps of: selecting the type of heat transfer
device from, for example,
conventional heat pipes, advanced heat pipes, thermosyphons, spreader
heatpipes, loop heat
pipes, pulsating heat pipes, steam pipes, any such combination, or the like;
selecting a method of
joining heat transfer device elements from, for example, soldering, brazing,
welding, threading,
foil winding, mechanical fittings, encapsulating thermal fluids, any
combination, or the like;
selecting a type of wick structure from, for example, sintered metal, axial
wick, metal screens,
grooves, any combination, or the like, or no wick material; selecting the
internal working
material from, for example, aqueous solutions, eutectic salt mixtures, organic
thermal fluids, or
high-temperature metals and alloys that can liquefy at temperatures in the
range of -40 C to
1,300 C, solids that sublimate, or materials with different chemical
hydration levels; and
additionally the methods can include applying the joining method, wick
structure, and working
fluid thus selected; and sealing the heat transfer device under vacuum.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG 1 Shows a possible power plant configuration.
[0033] FIG 2 Shows a ductwork configuration.
[0034] FIG 3 shows aerodynamic shapes of heat pipes to minimize drag
forces.
[0035] FIG 4 Illustrates a ductwork configuration for minimal pressure
drop.
[0036] FIG 5 Shows an optional configuration for heat recovery from a
baghouse.
[0037] FIG 6 Shows an optional configuration for heat recovery from an
electrostatic
precipitator (ESP).
[0038] FIG 7 shows an optional heat capture configuration from
intermittent heat
sources.
[0039] FIG 8 Shows a ductwork configuration for heat storage.
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[0040] Figure 9 Shows two optional configurations for recovering heat
from the
Bayer Process.
[0041] FIG 10 illustrates a cross sectional view of an embodiment of a
heat transfer
method for EOR.
[0042] FIG 11 is a cross sectional view of an embodiment describing the
installation
of a heat transfer device for EOR.
[0043] FIG 12 shows an alternative embodiment of an installation method
of heat
transfer device for EOR.
[0044] FIG 13 illustrates embodiments of heat transfer devices for
geothermal
installations.
[0045] FIG 14 shows and alternative embodiment of a heat transfer device
for
industrial plants.
[0046] FIG 15 are diagrams of a heat transfer devices with a thermal
insulation.
[0047] FIG 16 illustrates a cross sectional view of a heat pipe.
[0048] FIG 17 is a schematic view of a high-performance heat pipe.
[0049] FIG 18 illustrates two schematic diagrams of heat pipes.
[0050] FIG 19 illustrates an alternative embodiment for long distance
heat transfer.
[0051] FIG 20 is a diagram of a method for making long heat pipes.
[0052] FIG 21 is a cross sectional view of an alternative embodiment of
a winding
strip with a porous capillary surface.
[0053] FIG 22 illustrates an alternative embodiment for making long heat
pipes.
[0054] FIG 23 illustrates an embodiment of an axial wick for heat pipes.
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[0055] FIG 24 illustrates an embodiment for maintaining internal vacuum
in heat
pipes.
[0056] FIG 25 shows an alternative embodiment for making advanced heat
pipes.
[0057] FIG 26 shows an alternative embodiment for ultra-long advanced
heat pipes.
[0058] FIG 27 illustrates a heat pipe joining method.
[0059] FIG 28 illustrates a method for interrupting heat transfer in a
complex heat
pipe.
[0060] FIG 29 is a schematic of a heat transfer device.
DETAILED DESCRIPTION
Definitions
[0061] Thermal energy or heat (in common usage) represents the thermal
energy of
molecules, atoms or ions including kinetic, vibrational and rotational forms
of energy. Heat also
represents the transfer of kinetic energy from one medium or object to
another, or from an energy
source to a medium or object. Such energy transfer can occur in three ways:
radiation,
conduction, and convection but here will be used in a general common sense to
include available
thermal energy content. Some believe heat refers to the transfer of energy
between systems (or
bodies), not to energy contained within the systems, but this understanding is
unnecessarily
restrictive. Others define heat as the form of energy that flows between two
samples of matter
due to their difference in temperature, and that is also restrictive. The
following definitions of
heat are useful:
a. A form of energy associated with the motion of atoms or molecules and
capable of
being transmitted through solid and fluid media by conduction, through fluid
media by
convection, and through empty space by radiation.
b. The transfer of energy from one body to another as a result of a difference
in
temperature or a change in phase.
c. Thermal energy either latent or sensible.
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[0062] "Heat transfer devices" (HTDs), in the context of the current
invention,
include conventional and novel HP. spreader HP, thermosyphons, steam pipes,
and pulsating heat
pipes. When heat pipes are mentioned as the method of heat capture, transfer
and release,
pulsating heat and pipes spreader heat pipes can also be used. In vertical
applications,
thermosyphons can be used in place of heat pipes. Heat pipes are devices that
can capture,
transfer, and deliver heat more effectively than heat exchangers, metal
surfaces, or thermal fluids
because they operate on two physical principles and not just on thermal
conductivity. During heat
capture and release, heat pipes rely on both thermal conductivity and phase
change, but the latter
is several times more effective than the former, so the overall thermal
performance is many times
better than a comparable heat exchanger with similar surface area in the
applications under
discussion. Furthermore, during heat transfer, the ability of a heat pipe to
transfer heat by mass
transfer is, again, many times greater than the speed of thermal conductivity
alone, even when
dealing with highly conductive materials such as copper or silver. The
superior performance of
heat pipes over thermal fluids in the applications under discussion stems from
the difference in
specific heats of a common working fluid in heat pipes¨water¨versus the heat
capacity of
organic liquids in the case of thermal fluids.
[0063] An important feature of HTDs described in the current invention
is the
superior heat transfer mechanisms of the heat pipes. As shown in subsequent
paragraphs, heat
pipes provide a means of transferring heat that is near thermodynamically
reversible, i.e., a
system that transfers enthalpy with almost no losses in efficiency.
Furthermore, while
conventional heat pipes share these unique mechanisms, the advanced heat pipes
described
herein are characterized by significantly improved heat capture, transfer, and
release performance
and, thus, by approaching a thermodynamically reversible process even closer.
[0064] There is a need for an inexpensive heat-transfer mechanism that
can readily
transport heat at elevated temperature from surface operations, that can
deliver such heat at
constant temperature over a long period of time to underground formations,
that requires little or
no maintenance, that is reliable, and that requires minimal water or steam for
operation.
[0065] Commercially available heat pipes come in lengths of a fraction
of an inch to
several feet, but not in hundreds or thousands of feet, and there is a reason
for that. As explained
in sections of the detailed description, below, an essential aspect of a heat
pipe is its ability to
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circulate the condensed working fluid back to the hot area of the heat pipe.
That ability is quite
difficult to accomplish with current manufacturing processes, because a)
capillarity forces in the
current HP would not be able to lift the liquid hundreds of feet and, b) any
interruption in the
internal capillary action would also interrupt the internal transfer
mechanism. Therefore, there is
a need for long heat pipes that can be made to function effectively.
Heat capture using heat pipes, spreader heat pipes, thermosyphons, and
pulsating heat
pipes
[0066] Figure 29 is a schematic of a heat transfer device, for example a
type of heat
pipe. In FIG 29 the heat pipe (4) is composed of three major sections: a heat
capture section (4'),
a heat transfer section (4"), and a heat release section (4¨). The heat
transfer section is normally
called the "adiabatic" section because heat losses are so small that they are
normally ignored, so
the term adiabatic is used, although heat losses in adiabatic processes are
never really zero.
[0067] Embodiments of the invention are disclosed herein, in some cases
in
exemplary form or by reference to one or more Figures. However, any such
disclosure of a
particular embodiment is exemplary only, and is not indicative of the full
scope of the invention.
[0068] Industrial heat capture entails: (a) the capture of waste and/or
low-grade
thermal (heat) energy, such as hot flue gases, (b) cooling of various
industrial and chemical
processes, such as those that include exothermic reactions, (c) controlling
temperature in certain
chemical or petrochemical plants, such as controlling the oxidation of
propylene oxide at 200 C
during the production of propylene glycol, (d) using heat capture for delivery
at remote locations,
such as in enhanced oil recovery (EOR), and (e) capturing heat from difficult
to access locations,
such as tapping geothermal sources. Applicants review these by means of
examples that illustrate
the broad scope of the invention in various applications.
Capturing Waste, Low-, and High-Grade Thermal Energy
[0069] These industrial applications normally encompass large amounts of
heat at
temperatures that range from about 60 C to perhaps as high as 250 C which
hinders the
utilization of such energy for other heat consuming applications, such as
additional power
generation. The industries that generate large amounts of low-grade heat
include but are not
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limited to (a) those that use large amounts of fuel and generate large amounts
of flue gases, such
as power plants, especially coal-fired plants, metallurgical and cement
plants, and that dispose of
those flue gases by means of stacks or chimneys (b) those that use industrial
kilns, calcination
furnaces, or process reactors, such as lime producers, alumina producers,
magnesia producers,
and many inorganic chemical producers (c) those that generate large amounts of
heat without flue
gases, such as nuclear power plants, compressors, power transformers,
refractory plants,
glassmaking plants, or thermal power plants with their large heat producing
condensers.
[0070] Since fuel combustion constitutes a large fraction of energy
generation from
industry, capturing heat from flue gases becomes a relevant application for
many industries. The
recovery of heat from the flue gas of coal-fired power plants is selected to
illustrate heat capture
methods and mechanism.
[0071] Figure 1 illustrates a typical configuration for recovering heat
from such flue
gases. In Figure 1, the cross section of a typical flue gas duct (52) is a
rectangular cross section
measuring about 20x30 feet. A number of heat pipes (4) penetrate the section
of the flue gas (52).
The heat pipes are in contact with the flue gas, which is at temperatures of
300 F to 450 F, and
capture a fraction of the available heat in the gas. Capturing only a fraction
of the available heat
is an important feature in this particular application, because the
temperature of the flue gases
cannot be allowed to drop excessively. Such a drop would impair the eventual
flow of flue gases
through the disposal chimney. The heat pipes (4) that capture heat are
connected to a larger and
more complex heat pipe (58). This heat pipe has a larger diameter and, thus,
greater capacity for
transferring large amounts of heat. Alternatively, one can use different wick
structures that are
more efficient at long distances. The larger diameter heat pipe (58) transfers
the captured heat to
another location where such heat is fed into a set of smaller diameter heat
pipes (4) which in turn
deliver such heat to a process vessel (53) that requires heat, such as, for
example, the heat input
section of a water purification system. Thus, an important function of heat
capture involves using
heat pipes that can transfer heat from the flue gases and deliver it to other
processes that are at a
distance from the original flue gas heat source.
[0072] Figure 2 illustrates optional configurations for inserting heat
capture devices
into ductwork. As shown in figure 2, the heat capture devices (4) (e.g.,
conventional heat pipes,
thermosyphons, spread heat pipes, or pulsating heat pipes) are inserted part
way into the cross
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section of the flue gas duct (52) either vertically as illustrated in Figure
2(a) or horizontally as
shown in Figure 2(b). In preferred configurations, heat pipes are placed co-
linearly with the
direction of flow of the flue gases so as to minimize the drag forces and,
thus, the pressure drop
in the flue gas and potential erosion of the HP. Optionally, heat pipes can be
alternated between
the vertical and horizontal direction, or at intermediate insertion angles. In
addition, heat pipes
can be placed adjacent or staggered to each other to minimize turbulence and
pressure drop and
the thickness of boundary layers so as to maximize heat transfer from the bulk
of the gas to the
surface of the heat pipe.
[0073] Figure 3 illustrates another feature of heat pipes that is useful
for minimizing
drag in fluid flow: the thermal performance of a heat pipe is independent of
the cross-sectional
shape of the heat pipe, that is, the transfer of heat is primarily dependent
on the cross sectional
area and the surface area of the heat pipe, and far less on whether the cross-
section is circular,
rectangular, or another shape as long as the thickness of the gas boundary
layer and residence
times are similar. Figure 3 shows a cross section of the flue gas duct (52)
with a series of heat
pipes (4) with cross sectional shapes that aero-dynamically designed to
minimize drag, boundary
layer thickness and maximum contact time. Thus the leading heat pipe (4) has a
different cross-
section than the last heat pipe (4') in the row.
[0074] Figure 4 illustrates another method for minimizing drag in fluid
flow. In
Figure 4, the heat pipes (4) are inserted at an angle with respect to the
direction of flue gas flow.
Normally, drag forces and erosion are minimized when this angle is about 30
from the direction
of flow, although other angles may be preferred depending on the configuration
of the ductwork.
[0075] Typically in a coal fired power plant, the combustion gases are
first subject to
catalytic denitrification by means of ammonia or amines, then ash in the flue
gases is reduced by
either filtration in a baghouse or electrostatic precipitation. Subsequently,
the flue gases are
conveyed by means of the flue duct into a fan that increases the pressure
prior to flue-gas
desulfurization (FGD). Following FGD, the flue gases are vented to the
atmosphere by means of
a stack or chimney, which is another point of potential capture for low-grade
heat. Figure 5
shows an alternative configuration for capturing heat directly from ductwork
in a coal fired
power plant, that is, capturing heat at the baghouse (66). In Figure 5, the
heat pipes (4) are placed
inside (the clean side) the filters of the baghouse (66) in order to minimize
ash deposition onto
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the heat pipes. The flows of the flue gas and the flows of the fluid inside
the heat pipes will be
parallel and concurrent. The hot gas will contact the heat pipe and heat
captured at the bottom of
the heat pipe, will be rapidly transferred outside the baghouse area. which
will initiate cooling of
the flue gas. The total pressure drop of the flow in the filter bag will be
proportional to the
inverse of the free cross-sectional area inside the bag. For a 1 cm diameter
heat pipe inside a 10
cm diameter ceramic filter, the additional pressure drop due to the heat pipe
will be: 102/(102 -
12) - 1 or approximately a 1 % extra pressure drop. If one places 6 heat
pipes, one still has
102/(102 ¨ 6 x 12) ¨ 1 or approximately a 6% increase in pressure drop, which
is within the
margins of fluctuation of the flue gas system. The number, distribution and
diameter of heat
pipes will be determined by the dimensions of the filter bags and the desired
fraction of heat to
be recovered.
[0076] Figure 6 shows still another optional configuration for capturing
heat directly
from ductwork in a coal-fired power plant, that is, capturing heat at the
electrostatic precipitator
(67). The electrostatic precipitator system is designed to have maximum area
of contact with the
flue gas to be able to charge most of the particles flowing by with a minimum
pressure drop.
Therefore, the contact gas-solid contact is already good. A preferred
configuration is to make the
perforated plates (see Figure 6) to be heat pipes. The plates already have
connection to the
external electrical powering system, so the across the roof connections could
also be used as heat
transfer conduits, the HP themselves. Figure 6 illustrates the proposed
configuration in an
electrostatic precipitator. Since no changes in the flue gas flow are
considered, the pressure drop
in this particular configuration would be that of the electrostatic
precipitator without any further
increase.
[0077] The benefits of these last two configurations¨capturing heat at
the baghouse
or at the electrostatic precipitator¨are twofold: first heat is captured at a
slightly higher
temperature than in the flue-gas duct thus improving thermal efficiency, and
second each of these
process units can be used to perform dual functions, their original function
and the additional
heat capture function. Note also that since with the use of HP, the
electrostatic precipitator will
be kept at a lower temperature than in the conventional mode and as
consequence it will attract
more and even finer particles driven by thermo-foretic forces thus further
enhancing the filtering
action.
[0078] Industrial operations that generate large amounts of heat
intermittently
constitute a special case. Those operations occur in such industries as
integrated steel plants that
utilize oxygen converters, secondary steel plants that use electric furnaces,
and non-ferrous plants
that produce metals like copper, lead, silicon, or titanium. The processes in
these plants all
generate large amounts of heat at very high temperatures but not necessarily
continuously. The
capture of this type of intermittently produced heat is similar to previous
examples described
above, but the transfer and release of such heat presents restrictions that
are not found in
continuous heat sources. One option is to capture heat for use in applications
that also operate
intermittently. Another is to store the intermittent heat in a separate vessel
filled with a thermal
fluid: DowTherm or equivalent for medium to low temperatures, molten salts or
eutectics for
higher temperatures, or advanced heat storage systems, such as "Heat Transfer
Interphase," filed
12 January of 2011, with priority date of 12 January of 2010, and with the
International
Application Number of PCT/US2011/021007, and assigned to Sylvan Source, Inc.
[0079] Thus, it is clear that there is a dual industrial need: (a) the
need for novel heat
pipes that capture, transfer, and release thermal energy over long distances,
including vertical
distance, and (b) the need for storing thermal energy from high-temperature
sources that are
intermittent. The combination of such dual features opens up multiple
industrial applications that
are not possible otherwise.
[0080] Figure 7 illustrates heat capture from an oxygen converter, which
is normally
used in integrated steel plants, as well as in copper and lead plants. In
Figure 7, an oxygen steel
converter (71) contains molten iron (72) saturated with carbon and covered by
a thin layer of slag
(73). Oxygen gas is blown into the molten iron by means of an oxygen lance
((74) for periods on
the order of 20 to 30 minutes and, during this operation, copious amounts of
combustion gases
(75) containing CO and CO2 evolve at very high temperature, higher than 1.500
C. Such
combustion gases (75) are collected above the converter by a hood (76) and
carried away by a
metal duct (77). The duct is enlarged in order to fit a number of heat pipes
(4) that capture part
of the heat and transfer it to a storage tank (54) filled with a thermal fluid
that may include
molten salts or eutectics that are stable at those temperatures. Suitable
compositions for those
16
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molten salts and eutectics are described in South African Patent No.
2012/05975, Issued on May
29, 2013.
[0081] Figure 8 illustrates another example of heat storage, but one
that applies to
continuous heat generation. Figure 8 shows an optional configuration for
capturing and
transferring heat from the ductwork (52) of a power plant into a storage
vessel (54) that allows
interruption of heat transfer by simply opening valve (56) thus draining the
thermal storage tank
into a lower vessel (55). When the thermal fluid is in the lower vessel, heat
is no longer being
captured from the ductwork. The thermal fluid is stored until it is needed
again to capture more
heat, at which point pump (57) activates and the thermal fluid is pumped up to
the vessel (54)
and again allowed to come in contact with the heat pipes (4). In addition, the
thermal fluid tank
(54) allows a large-diameter heat pipe (58) to capture the heat of the thermal
fluid so it can be
transferred away for potential use, such as in water purification.
Cooling of Industrial and Chemical Processes
[0082] Numerous industrial applications require capturing heat as a
means of cooling
and refrigeration. Such industries include but are not limited to icemaking,
brewing, underground
mining, pulp and paper manufacture, food processing, beverage production,
dewatering during
biofuel production , and the cooling of chemical and petrochemical reactions
that are exothermic
such as in the production of cellulose acetate, nitrobenzene, polyvinyl-
chloride resins, carbon
disulfide, cumene (from alkylation of benzene with propylene), ethyl alcohol
(from hydration of
ethylene), formaldehyde (from methanol using exothermic reactor), phenol (from
cumene
peroxidation), and propylene glycol (by hydration of propylene oxide at 200
C), acrylic resins
(from catalytic oxidation of methyl methacrylate), aromatic ketone polymers
(from condensation
polymerization reactions), copolyester-ether elastomers ,and polyacetal
resins, to name a few.
[0083] Many industrial cooling operations employ double walled reactors
where the
outer vessel contains a circulating coolant, such as water or a thermal fluid,
that takes away
excess heat from the inner reactor, thus preventing run-away reactions from
exothermic
operations. Figure 9 illustrates a typical double-walled reactor for cooling,
and while the example
covers the digestion of bauxite into sodium aluminate as a first step in
making alumina, it could
also cover many double-walled reactors used for cooling industrial processes.
In Figure 9, two
alternative configurations are presented. Figure 9(a) illustrates a
conventional double-wall
17
reactor, where the outer vessel (64) is filled with a thermal cooling fluid
(typically water), and
surrounds the inner reactor (63) where bauxite is digested with caustic
(NaOH). The reactor top
(65) closes the reactor and maintains pressure and temperature. The thermal
fluid is kept
circulating by pump (57), while a heat pipe (4) conducts heat away from the
thermal fluid for
possible use elsewhere.
[0084] Figure 9(b) illustrates an alternative embodiment where the outer
vessel is
replaced by a cylindrically shaped heat pipe (4) that contains a capillary
wick (12) throughout its
entire inner surface area, thus accelerating the capture of heat and its
transport away from reactor.
This type of complex heat pipe (58) is discussed in subsequent paragraphs. In
cooling
applications the working fluid of the heat pipe need not be water or aqueous
fluids, but can be
cryogenic fluids, such as ammonia and the like. Other alternative
configurations for capturing
heat in cooling and refrigerating applications are covered in South African
Patent No.
2012/05975, Issued on May 29, 2013.
[00851 Cooling towers are generally used for cooling excess heat in
thermal power
plants and are commonly employed throughout the chemical and petrochemical
industry. Cooling
towers dissipate heat by evaporation and therefore, substantially contribute
to water losses in an
industrial operation. Heat pipes can be used for the augmentation and
replacement of cooling
towers because of their superior performance in capturing, transferring, and
releasing heat. Thus,
heat pipes can capture heat from fluids (gases or liquids) before they enter
the cooling tower, thus
augmenting the capacity of the cooling tower and, if sufficient heat is
captured the cooling tower
may be eliminated altogether.
Controlling Temperature in Chemical or Petrochemical plants
[0086] Many chemical and petrochemical industries require precise
control of
operating temperature. In this invention, the means of controlling temperature
are similar to
those considered in Figure 9 above, where cooling is done in double-walled
reactors. Industries
requiring close temperature control include but are not limited to
acetaldehyde (from oxidation of
ethylene), acetic acid (from carbonilation of methanol), acetone (from
catalytic dehydrogenation
of isopropyl alcohol), acrylic acid (from propylene oxidation), acrylonitrile
(from ammoxidation
of propylene), adipic acid (from cyclohexane oxidation), plasticizer alcohols
(from
hydroformilation of olefins), alkyl amines (from alcohol/ammonia reactions),
benzene (from
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hydrodealkylation of toluene, 1-4 butanediol (from acetylene/formaldehyde
reaction), carbon
disulfide (from natural gas and sulfur reaction), carbon fibers,
carboxymethylcellulose (CMC),
cellulose acetate and tri-acetate fibers, chlorinated isocyanurates (from urea
pyrolysis), C2
chlorinated solvents (from chlorination of ethylene dichloride), chlorinated
methanes. cumene
(from alkylation of benzene with propylene), cyclohexane (from hydrogenation
of benzene with
hydrogen), di isocyanates and polyisocyanates (from phosgenation of primary
amines), ethyl
alcohol (from hydration of ethylene), ethyl benzene (from the alkylation of
benzene by ethylene),
ethylene dichloride (from reacting ethylene with oxygen and hydrogen
chloride), ethylene oxide
(from oxidation of ethylene), formaldehyde (from methanol using exothermic
reactor), hydrogen
cyanide, isopropyl alcohol (from hydration of propylene with superheated
steam),
ketene/diketene (from vapor-phase cracking of acetic acid), linear alkylate
sulfonates (from
sulfonation of linear alkyl benzene with oleum or with sulfur trioxide in
sulfuric acid), linear
alpha olefins (from ethylene oligomerization), maleic anhydride (from vapor-
phase oxidation of
hydrocarbons), methanol (from synthesis gas and carbon dioxide), methyl ethyl
ketone (from the
catalytic dehydrogenation of secondary butyl alcohol), phenol (from cumene
peroxidation),
phosgene (by reacting anhydrous chlorine gas and carbon monoxide), phthalic
anhydride (by
reacting xylene with oxygen), polyester fibers, polyester polyols (by
condensation of a glycol and
a carboxylic acid or acid derivative), polyethylene, polyglycols for
urethanes, polyimides,
propylene glycol (by hydration of propylene oxide at 200 C), propylene oxide
(from chlorohydrin
or peroxidation), pyridine and pyridine bases (by reacting acetaldehyde -
usually with methanol or
formaldehyde- with ammonia), sorbitol (by high-pressure catalytic
hydrogenation of glucose in
autoclaves), terephthalic acid and dimethyl terephthalate, urea, acrylic
elastomers,acrylic resins
(from catalytic oxidation of methyl methacrulate), amino resins (from the
reaction of aldehydes
and amino groups), aromatic ketone polymers (from condensation polymerization
reactions),
fluoropolymers (from tetrafluoroethylene reacting with acid, and surfactants),
copolyester-ether
elastomers, nylon resins, polyamide resins, polyacetal resins, polycarbonate
resins, PBT resins
(from bi s- (4-h ydrox ybutyl )-terephth al ate-BHBT), PET polymers (by pol yc
on den s ati on of
ethylene glycol with either dimethylterephthalate or terephthalic acid),
unsaturated polyester
resins, and polystyrene resins (using free-radical polymerization of styrene
with an initiator and
heat)
Using Heat Capture for Delivery at Remote Locations
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[0087] Embodiments of the invention include systems, methods, and
apparatus for
heating underground geological formations, such as oil deposits (e.g.,
enhanced oil recovery-
EOR), without requiring water, CO2, or steam injection. Preferred embodiments
provide a broad
spectrum of heat pipes that operate within the temperature range of 120 C and
1,300 C or
higher, and that provide for fully automated heat recovery at temperatures
similar to that range
over several hours, days or months without user intervention. For example,
systems disclosed
herein can run without user control or intervention for 1, 2, 4, 6. 8, months,
or longer. In
preferred embodiments, the systems can run automatically for 1, 2, 3, 4, 5, 6,
7, 8 years, or more.
[0088] Figure 10 illustrates the use of a heat pipe for purposes of EOR.
In Figure 10,
the surface site (1) is assumed to have a drill hole (3) that was already in
place or drilled
specifically for the heat pipe, and a heat pipe (4) that reaches from the
surface to the oil
formation (2). During operation, heat is provided to the top of the heat pipe.
The heat pipe
efficiently transfers such heat directly from its top to its lower portion
which is in contact with
the oil strata. Since sedimentary oil formations can be located at substantial
depth, the heat pipe
(4) must be sufficiently long for it to reach into that formation. Therefore,
an important problem
to solve is how to design and manufacture such HP and how to insert a very
long pipe into a
vertical or inclined drill hole without excessively bending the pipe and thus
damaging it.
[0089] Figure 11 describes one possible method for placing a long heat
pipe into a
drill hole. In Figure 11, a number of buoyant balloons (5) are used at
suitable intervals along the
length of the pipe (4) to neutralize its weight and thus prevent it from
bending when lifting one of
its ends. The actual lifting can be done with a helicopter (6) or similar
airborne system (e.g., a
drone). Once the heat pipe is aligned with the drill hole (3), its neutral
weight makes it easy to
lower it into position, gradually removing the individual lifting devices (5)
from the pipe (4),
until the pipe reaches the oil formation (2).
[0090] Figure 12 shows an alternative embodiment for placing a heat pipe
down a
drill hole. In Figure 11, the heat pipe 4 is wound around a circular wheel 25
with sufficient radius
to minimize the curvature of the pipe and thus prevent damage to its internal
mechanism. As the
wheel is rotated, the heat pipe is then lowered into the drill hole 3.
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[0091] Once in place, the heat pipe is ready for transferring heat from
the surface to
the oil formation directly without the need for pumps, external recirculation
loops, or other
mechanisms. Heat can be provided to the upper portion of the pipe on the
surface by direct
combustion of fuels (e.g., natural gas, oil), by solar heating through solar
concentrators or
parabolic troughs, electrical, geothermal sources, steam, waste heat at
elevated temperatures, or
any other type of energy source. Since heat pipes excel at axial heat transfer
at rates that approach
the speed of sound, the heat absorbed from surface sources rapidly reaches the
oil formation
where such heat is released.
[0092] An optional configuration entails using a heat pipe as described
in the above
paragraph together with steam injection. This allows the steam to maintain a
high temperature
throughout the length of the heat pipe, thus minimizing wall heat losses,
while enhancing heat
transfer and delivering higher temperature heat at the bottom of the heat
pipe. In addition, steam
condensation provides liquid water at the oil formation that enhances flow.
This type of
configuration can prove useful when there is a need for additional heat
delivery or when the
number of drill holes for EOR is limited.
Using Heat Capture for Delivery in Geothermal Fields
[0093] In other applications, such as the recovery of heat from
geothermal fields,
preferred embodiments include either heat pipes, thermosyphons, loop heat
pipes, or pulsating
heat pipes that operate within the temperature range of 250 C and 1,300 C
and that provide for
fully automated heat recovery at temperatures similar to that range over
several hours, days or
months without user intervention.
[0094] Figure 13 illustrates two embodiment options for extracting heat
from a
geothermal field. Geothermal sources typically derive heat energy from a deep
magma chamber
(27) (not drawn to scale in Figure 13), which heat a geothermal formation (26)
that may have
significant moisture or be substantially dry. Figure 13(a) assumes a wet
geothermal formation, so
that liquid water in the drill hole (3) can transfer heat directly to the heat
pipe, pulsating heat
pipe, or thermosyphon (4). As demonstrated in subsequent paragraphs, the heat
pipe,
thermosyphon, or pulsating heat pipe (4) provides a highly efficient mechanism
for heat transfer
from the geothermal formation (26) to the surface, where such heat can be
recovered at
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temperatures similar to those prevailing at depth and utilized directly
without the need for either
heat exchangers or water treatment.
[0095] Figure 13(b) illustrates an alternative embodiment for geothermal
heat
recovery when the geological formation is either very dense, or has low
porosity or permeability,
or lacks sufficient moisture to assist in heat conduction at depth. In those
cases, the bottom of the
drill hole (3) is enlarged at the bottom (28) in order to provide a greater
surface area for thermal
conductivity. To further increase thermal conductivity, this bottom portion of
the hole can be
partially filled with water (29) or other high thermal conductivity fluids.
Furthermore, in order to
preserve the high temperature in a geothermal field, it would be advantageous
to cap the drill-
hole at the top with a valve (30), so as to maintain the pressure and
temperature prevailing at the
geothermal depth, thus allowing the heat pipe, pulsating heat pipe, or
thermosyphon (4) to
transfer heat at the maximum possible temperature to the surface.
Description of Heat Transfer from an Industrial Source
[0096] Other embodiments capture heat from industrial plants and
transfer it to sites
that can use that heat at distances of tens to hundreds to thousands of feet.
These systems can
operate within the temperature range of 80 C and 1,300 C and provide for
fully automated heat
recovery at temperatures similar to that range over several hours, days or
months without user
intervention.
[0097] Figure 14 shows an embodiment for transferring heat in an
industrial setting.
In a typical industrial plant (31), a source of waste heat (32), which can
include a power plant, a
boiler house, an exothermic process vessel, or a chemical reactor that can be
used to provide heat
by means of heat pipes (4) which transfer such heat with minimal losses in
temperature to remote
places (33) which can include steam generation sites or other process vessels
that require heat.
[0098] The chemical process industry covers many hundreds of chemicals
and
petrochemicals that either utilize highly exothermic processes, require
temperatures of several
hundreds of degree centigrade, or produce products that must be cooled or
refrigerated rapidly.
Examples include but are not limited to the manufacture of acetaldehyde,
acetic acid, acetic
anhydride, acetone, acetonitrile, acetylene, acrylamide, acrylic acid,
acrylonitrile, adipic acid,
alkyl amines, alkylbenzene, ammonia, aniline, ketone polymers, benzene,
benzylchloride,
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bisphenol A, beutanediol, butylacetate, caprolactam, carbon disulfide,
cellolose acetate. cellulose
ethers, chlorinated isocyanurates, chlorinated solvents, chlorobenzenes,
chlorinated methanes,
cresols, xylenols, cumene, cyclohexane, dimethylformamide, epichlorohydrin,
epoxy resins,
ethanolamines, ethyl acetate, ethanol, ethyl benzene, ethylchloride, ethylene,
ethylene dichloride,
ethylene amines, ethylene glycol, ethylene oxide, fluorocarbons, formaldehyde,
fumaric acid,
furfural, glycol ethers, Hexamethylenediamine, hydrogen cyanide, hydroquinone,
isophthalic
acid, isopropyl alcohol, ketene, alkylsulfonates, alphaolefins,
lignosulfonates, maleic anhydride,
melamine, methanol, methylethyl ketone, methyl methacrylate, nitrobenzene,
Nylon resins,
phenol, phenolic resins, phosgene, phthalic anhydride, polyamide resins,
polyacetal resins,
polyalkylene glycols, polycarbonate resins, polyesters, polyethylene,
polyglycols, polyimides,
polypropylene, polystyrene, polyvinyl alcohols, propionic acid, propylene
glycol, propylene
oxide, pyridine, silicones, sorbitol, styrene, terephthalic acid, urea, vinyl
acetate, vinyl chloride,
and zeolites.
[0099] Another type of industrial application involves power plants,
particularly those
fueled by coal. These plants generate substantial volumes of combustion gases
that require
progressive treatment steps to reduce pollutants. Typically nitrogen oxides
(N0x) are generated
during the combustion process and need to be reduced by adding ammonia or
amines which
reduce the NOx to nitrogen gas. Next, the fly ash particles need to be
captured and removed,
which is normally done with electrostatic precipitators or baghouses, or both.
The flue gases also
contain significant sulfur compounds from the original coal, which is normally
handled in a flue
gas desulfurization (FGD) system involving scrubbing. In spite of these
various treatment steps,
the flue gas in a coal-fired power plant contains very large amounts of low-
grade heat at
temperatures in the range of 330 F to 400 F that can be tapped without
unduly affecting the
normal operation of the plant.
[00100] Other examples of heat capture, transfer, and release include:
In thermal power plants,
= The augmentation and replacement of cooling towers
= The augmentation and replacement of large condensers
= Extracting heat as steam and "hot furnace gas" to optimize cycle
efficiency
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= Recovering heat from the boiler house in small power plants
= In hot-pond power generation, using heat pipes to transfer heat
= Preheating pre-combustion gases
= Capturing heat from boiler blow-down
In nuclear power plants,
= Cooling of spent-fuel storage
= Cooling of reactor core
= Augmentation and replacement of steam condensers
In natural gas compression stations
= Recovering heat from large compressors
In underground mining
= Cooling deep working sites
In solution mining
= Heating underground formation to increase solubility
In plywood and OBS production
= Drying of raw materials
In the heat management of industrial processes, such as
= bio-fermentation
= fertilizer production (e.g., urea)
In industrial gas production
= Compressor heat in argon, nitrogen, oxygen, CO, production
= Gas liquification
= Coal gasification and syngas ¨ Fischer-Tropsch process
In military applications, such as
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= Stationary generators
= Mobile engines, such as vehicles
= Engines on ships
= Mobile/deployable heat pipe runway for both, cooling and heating
In solar applications
= Capturing, transferring, and releasing heat in solar concentrators
= Cooling of photovoltaic arrays
In metallurgical applications
= Crystal pulling (e.g., silicon) using radian heat
= Continuous casting of steel and other metals using radiant heat and
conduction
= Heat shielding by transferring heat away from the heat shield
= Cooling the molds in sand casting
= Cooling the laser head in laser cutting
Miscellaneous other applications, including heat sensitive industries in SIC
code,
such as
= Heat recovery from semi-conductor processing
= Rubber manufacturing, e.g., vulcanizing
= Oil refineries, including coker, distillation towers, and chemical
reactors
= Augmenting and replacing HVAC systems for cooling and heating of
residential
and industrial buildings
= Freeze protection for agricultural applications, such as grapes and
citrus.
= Decomposing undersea methane hydrate for gas production.
[00101] Since any type of heat pipe is exceedingly effective at heat transfer,
the
following section focuses on heat pipes, and how to improve their average
performance so they
can be applied not only to conventional applications, such as stabilizing
Alaskan permafrost, but
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also in a variety of industrial applications including but not limited to
desalination, industrial
transfer of heat, cooling, refrigeration, and the like.
About Heat Pipes
[00102] Clearly, heat pipes allow effective thermal transfer to be done. The
heat pipes
are driven by the temperature difference between their condensing and boiling
ends (the AT)
which is sufficient to maintain a very high heat flux through the heat pipe.
Commercially
available heat pipes transfer large amounts of heat (e.g., >200 W) and
typically have ATs of the
order of 8 C (15 F), or higher at higher power output, although some have
ATs as low as 3 C.
The AT is not critical for EOR or geothermal applications because the
difference in temperature
between a surface heat source and the geological formation is several hundreds
of degrees, but a
low AT is generally desirable to optimize overall thermal efficiency. It is
therefore useful to
examine the thermal phenomena in a heat pipe. Insert working fluid here (92)
[00103] An important factor in maintaining a low AT is limiting the wall heat
losses,
which are a function of the surface area (and thus on the length) of the pipe
and the thermal
conductivity of the wall material and the media surrounding the HP. This need
is not critical for
normal HP pipes but is important for very long HP as claimed in this
application. Figure 15
illustrates different possible embodiments of surface insulation for a long
heat pipe so that most
of the heat is transferred to the cool end and very little is lost along the
walls of the HP in the
middle section. In the embodiment illustrated in Figure 15(a), a good
insulating coating (7) is
used over most of the surface area, except for the areas where the heat pipe
(4) either absorbs or
releases heat. Adequate insulators for relatively low temperature (<150 C)
include the thermal
insulator materials such as those used in steam pipes. Adequate insulators for
high temperature
operation can include various insulating bodies with ceramic compositions,
such as zirconia,
alumina, magnesia, and similar compositions. An optional configuration for
superior insulation is
shown in Figure 15(a) and entails a ceramic material containing close pores.
Figure 15(b) shows
another embodiment which consists of a tube enclosure (7) under partial
vacuum. This enclosure
provides superior thermal insulation, plus the advantage of an external vacuum
that neutralizes
the structural strain of the internal vacuum of the heat pipe. The type of
enclosure tube can be
similar to those utilized in the heat collector tube of parabolic solar
concentrators. Figure 15(b)
illustrates an embodiment that includes a structural support sleeve (24) that
surrounds the heat
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pipe (4) at regular intervals to prevent the weight of the heat pipe from
overcoming the structural
resistance of the heat pipe assembly, particularly for high temperature
operations. Such structural
support can serve the dual purpose of assisting in neutralizing the weight of
the heat pipe both
during its insertion into its final location and during operation.
[00104] Figure 15(c) illustrates another embodiment for extending the length
of heat
pipes with minimal loss of heat transfer performance. In Figure 15(c) the heat
pipe (4) ends with
a smaller diameter tube (40) that fits into a hollow semi-cylinder which is
the end of another heat
pipe. The surface area of the two heat pipes allows heat to transfer from one
heat pipe to another,
and thermal losses are minimized by a flexible insulating blanket (not shown).
Figure 15(d)
illustrates an alternative configuration for connecting two or more heat pipes
(4) into a longer
heat pipe using small diameter or capillary size endings of each heat pipe
(40). This type of
configuration utilizes a common feature of heat pipes, namely that the
internal shape of a heat
pipe has little influence on the heat transfer performance and functionality
of the heat pipe. Both
types of configuration lead to "articulated" heat pipes that are designed to
pivot and bend at the
junction of two or more heat pipes, thus allowing very long heat pipes to
follow a non-straight
path.
[00105] Figure 16 illustrates a typical commercial heat pipe (4), which
ordinarily
consists of a partially evacuated and sealed tube (10) containing a small
amount of a working
fluid (11) which is typically water, but which may also be an alcohol or other
volatile liquid.
When heat in the form of enthalpy is applied to the lower end of the heat
pipe, the heat first
crosses the metal barrier (10) and the internal wick (12) and then is used to
provide the heat of
vaporization to the working fluid (11) which permeates the entire surface of
the wick. As the
working fluid evaporates, the resulting gas (steam in the case of water) fills
the evacuated tube
and reaches the upper end of the heat pipe where the AT between the inside and
the outside of the
heat pipe causes condensation and, thus the release of the heat of
condensation to the outside of
the heat pipe. To facilitate continuous operation, the inside of tube (10)
normally includes a wick
(12) which can be any porous and hydrophilic layer that transfers the
condensed phase of the
working fluid back to the hot end of the tube.
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[00106] An improvement in the ability to capture heat is the use of metal
oxides and/or
pigments that are dark or black and that absorb heat more readily,
particularly in the case of
radiation heat. One advantage of a heat pipe having a black exterior coating
is that such black
surface also excels in radiating heat at the cold end of the heat pipe.
[00107] Experimentally, the largest barriers to heat transfer in a heat pipe
include: first
the layer immediately adjacent to the outside of the heat pipe (the boundary
layer), second the
conduction barrier presented by the material of the heat pipe, and third, the
limitation of the wick
material to return working fluid to the hot end of the heat pipe. However, in
EOR applications,
the boundary layer adjacent to the exterior of the heat pipe is minimal for
two reasons: first,
because if direct heating is used or steam or pressurized hot water are not
used, the thermal
barrier becomes far less significant, and second because, on the oil formation
side, any water
tends to be quite saline which can readily collapse the molecular double layer
responsible for
most of the barrier. Figure 17 illustrates a high-performance heat pipe that
minimizes these
barriers. Note that the axial wick reduces the thermal barrier normally
present in a conventional
wick that is adjacent to the wall of the heat pipe.
[00108] In Figure 17, the heat pipe (4) is shown in a vertical position with
the heat
input at the top and heat release at the bottom. The heat transfer barrier
that is adjacent to the
exterior of the heat pipe can be minimized as described in the above
paragraph. The heat
conduction barrier through the metal casing of the pipe can also be minimized
by using a very
thin metal foil (10) instead of the solid metal tube of most heat pipes.
Mechanical support for the
metal foil must be sufficient to sustain moderate vacuum and is provided by a
metal screen (13)
that provides additional functionality by increasing the internal surface area
available for
providing the necessary heat of condensation/evaporation. An internal wick
(12) is also provided
to assist in the evaporation of the internal fluid by its large surface area
and open porosity. Also,
given the long distance that the condensed working fluid must travel inside
the pipe, there is an
additional axial wick structure (14) at least partially not attached to the
walls that transfers fluid
through capillary action, but independently from the surface wick action.
[00109] During operation, heat enters near the top and traverses the thin
metal foil
(10). The thinness of the metal foil facilitates heat transfer because thermal
conductivity is an
inverse function of the thickness of the material through which heat must
travel. Upon reaching
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the internal wick (12), heat rapidly evaporates the working fluid that is
present in the wick. The
saturated vapor travels rapidly through the internal volume of the heat pipe
and reaches the
opposite end of the pipe where the slightly lower temperature causes the
condensation of the
vapor back into the working fluid. In the process, the heat of vaporization
has been transferred
from the top of the heat pipe to the bottom. The condensed working fluid then
flows by capillary
action toward the hot end of the pipe through both the surface wick (12) and
the central axial
wick (14), thus providing the necessary volume of flow for maintaining a large
heat transfer.
[00110] Figure 18 shows a graphical comparison of two heat pipes: one a
conventional
and one a novel design. In the conventional heat pipe, the main problem is
maintaining a wick
structure (12) uninterrupted over the entire length of the pipe. Ordinarily,
this is not a problem
with pipes a few feet in length or shorter. It becomes a serious difficulty
when the length exceeds
such dimensions. The novel design obviates this problem by having an axial
capillary wick (14)
that does not require sintering or high thermal conductivity, but that may
consist of any porous
material that is wettable by the internal working fluid. In either case, the
objective is to be able to
transfer heat energy efficiently from the heat source at the top of the heat
pipe to the application
area at the bottom of the heat pipe. That objective is difficult if not
impossible to achieve with a
conventional heat pipe, unless the internal wick can function without
interruption. Another
problem/limitation of HP is manufacturing very long tubes. Making long tubes
is normally
accomplished by either welding shorter tube lengths, or threading them, but in
either case, the
problem of leakage arises, especially when conventional pipes are partially
evacuated before final
assembly.
[00111] Internal wick materials include sintered copper spheres, metal groves,
metal
screens, and other materials that contain a well-defined porosity.
[00112] Figure 19 illustrates an alternative embodiment that obviates the need
for
extremely long heat pipes. In the cross sectional view of Figure 19, shorter
heat pipes (4) are
assembled with intermediate reservoirs (8) that contain a thermally conductive
fluid (9), which
transfers heat from one heat pipe to another, thus lengthening the distance
over which heat
transfer occurs. However, this embodiment requires that the intermediate
reservoir be
hermetically sealed to prevent loss of heat transfer fluid (9). In addition,
thermal losses will
necessarily increase with this type of embodiment because of the increase AT
at each junction,
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and the higher thermal wall losses due to the surface area of the intermediate
reservoir and its
temperature. Yet, the proposed embodiment offers a practical solution to heat
transfer over very
long distance, especially in EOR applications since pipe joining is a common
activity and high-
temperature heat is normally available. The type of transfer fluid can be any
heat conducting
liquid that is chemically stable at the temperatures involved in the heat
transfer junction, such as
DowTerm , certain eutectic salt mixtures, and the like. Those familiar with
the art will also
recognize that similar embodiments involving the joining of short heat pipes
into longer ones
while maintaining hermetic seals are also possible and therefore the proposed
embodiment is
merely exemplary and is not intended as a limitation on the scope of the
invention.
[00113] The composition of the working fluid inside a heat pipe generally
determines
the temperature range of the heat pipe or thermosyphon. Low temperatures
involve organic
compounds such as ammonia, alcohols, ketones, aldehydes, or aromatic
hydrocarbons that boil at
temperatures lower than ordinary water or aqueous solutions. For high-
temperature ranges,
certain metals like sodium, potassium, magnesium, aluminum, lead, zinc, and
their alloys provide
working fluids that can work at temperatures in excess of 1300 C. Another
option is to use salts
and mixtures of salt that sublimate as a working fluid for both, high and low
temperature heat
pipes. Also included are metal oxides, borates having different hydration
levels.
[00114] Figure 20 illustrates a method for making heat pipes of any length,
and one
that is especially suitable for the manufacture of very long heat pipes. The
method begins with a
tubular scaffold (13) made of a metal screen with wires that are strong enough
and openings that
are small enough to maintain structural integrity of the finished heat pipe
once it is sealed under
partial vacuum. Normally, mesh sizes of the metal screen in the range of 24 to
150 mesh could be
suitable to maintain partial vacuums of the order of 0.1 bar. If higher vacuum
is desirable, the
size of the metal screen can be down to 325-400 mesh, and one can provide a
double screen
surface with larger screen holes on the inside surface of the tubular scaffold
that will add rigidity
to the external screen surface. Those familiar with the art will realize that
there are different ways
to manufacture such tubular scaffold: it can be pre-formed which limits the
overall length to
several hundred feet, or it can be woven in situ for longer distances.
[00115] Once the tubular scaffold is formed, it is inserted into a
furnace (19) that can
sinter or weld the finished surface of the heat pipe which is allowed to
rotate, as shown in the
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diagram of Figure 20. Next, a metal strip (17) made of thin metal foil that
includes a slightly
thinner strip of sintered wick material (18) on one side is continuously wound
over the tubular
scaffold, so as to form a tube. The winding angle of the metallic strip (17)
will be determined by
the width of the strip (17), and the degree of strip overlapping required to
completely seal the
winding surfaces together. The furnace (19) is essentially the next to the
last step in forming a
tube with an inner wick layer. Once the tube is complete, an axial wick can be
placed, the
working fluid inserted, and the pipe can be evacuated and sealed.
Alternatively, the axial wick
and the tube can be manufacture simultaneously.
[00116] Figure 21 provides cross sectional views of two embodiments for
winding a
long distance tube with an inner wick surface. In Figure 20(a) the wick (18)
consists of strip of
sintered spheres (17), and shows two upper strips of a porous flexible weave
(20) that protrude
over the edge of the wick. When wound around the tubular scaffold the weaves
make contact
with adjacent weaves, thus providing a continuous porous layer that
constitutes a continuous
capillary surface. This prevents the inner wick material from being isolated
in any section of its
axial length. An alternative embodiment is described in Figure 21(b), where
the inner strip of
wick material is placed at a slight angle with respect to the vertical line,
so as to be wider than the
thin metal foil being wound, so as to ensure proper contact of the inner wick
material. Of course,
this can cause a slight separation between the thin metal foils during
winding, which can be
sealed with a thinner strip of foil (21) that is wound around the pipe just
before it enters the
welding furnace, as illustrated in Figure 22.
[00117] Figure 23 illustrates an embodiment of the axial wick (12) that may
consist of
a single cylindrical porous body, a coaxial cylinder with an inner metal wire
to provide rigidity, a
coaxial cylinder where the capillary action derives from small beads made of
glass, ceramic, or
metal, or combinations thereof. To prevent bending of the axial wick and
maintain its separation
from the inner walls of the heat pipe (4), a series of radially spaced
supports (22) is placed along
the length of the wick prior to its insertion into the heat pipe. Such
supports are generally thin
sections that do not unduly reduce the free inner volume of the heat pipe, and
thus do not reduce
the mass flow of vapor along the length of the heat pipe.
[00118] An alternative method for manufacturing a suitable wick is by using a
copper
or other metal precursor. A metal precursor is a chemical substance that upon
heating
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decomposes into a metal. In the case of sintered copper wicks, the precursor
can be copper beta
diketonate (CBDK) or copper acetylacetonate (CAA), both of which decompose
into micron-
sized copper particles upon heating in a reducing atmosphere. In general any
organic precursor
that can be decomposed, or any ionic precursor that can be electrodeposited
can be candidates. A
suitable wick can be made by slurrying micron-sized copper particles in CBDK
or CAA and
spreading the slurry into the inside surface of a copper tube or copper strip.
The excess liquid is
drained away, so the solid metal particles are subsequently held by surface
tension of the
funicular rings that form in the contact points of the metal particles. Upon
heating in a reducing
atmosphere, the CBDK or the CAA decomposes into copper that welds into the
contact points of
the metal particles, thus cementing them in place. Alternatively, providing a
suitable electro-
potential, Cu ions can be deposited to provide the desired glue. Numerous
metal precursors are
available for decomposition into different metals, and normal thermal
diffusion will allow such
precursors to cement similar and dissimilar metals, as long as the metallic
particles and the
precursor metal have some solubility with each other. For example, deposition
of CU on Cu or
Sn on Cu can both provide the good thermal contact via Cu or CuSn alloys
bridges.
[00119] Following the installation of the axial wick, which is optional but
desirable in
a long heat pipe, the working fluid is inserted so it can saturate the inner
surface of the wick and
the volume of the axial wick. The volume of working fluid can be 0% to 25%
higher than
required for wick saturation, and in cases where the evaporated working fluid
can become
superheated in its vapor form, the excess working fluid can exceed 25%.
[00120] A potential problem may arise with the wick structure in very long
vertical
heat pipes because of the need to maintain capillary action against the forces
of gravity. The
height of a capillary rise, h, is defined by:
h = 22 cos 0
pqr
where'? is the liquid-air surface tension (force/unit length), 0 is the
contact angle, p is the density
of liquid (mass/volume), g is local acceleration due to gravity (length/square
of time[26]), and r
is radius of tube.
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For a water-filled glass tube in air at standard laboratory conditions, y =
0.0728 N/m at 20 C, 0 =
00 (cos(0) = 1), p is 1000 kg/m3, and g = 9.81 m/s2. For these values, the
height of the water
column is
1L48 x I 0 --'
____________________________________________ m
[00121] Thus for r=0.0002 m (0.2 mm), h= 0.074 m, and for r= 0.000002 m (2
micron), h= 7.4 m, and for r= 0.000000002 m (2 nm), h = 7,400 m. However, in
actual industrial
practice laboratory conditions do not necessarily apply: the value of surface
tension normally
decreases with temperature and the contact angle is rarely 0 , although by
keeping the wick
surface clean and using working fluids that are aqueous such values can be
approached. The
largest factor in maintaining capillary action, however, remains the radius of
the capillary.
Therefore, the wick pore size in very long heat pipes needs to be in the range
of several
nanometers and not in the micron range as it is normal for conventional HP.
However, this is not
a problem encountered with pulsating heat pipes or thermosyphons that do not
have wick
structures. The practical implication in terms of manufacturability suggests
sintered wicks made
of nano-particles or the use of nanotubes or nano-sized structured powders or
films of similar
size.
[00122] The final stages in making a heat pipe involve evacuating it by
applying
vacuum, and sealing it by crimping or welding. Figure 24 illustrates an
alternative embodiment to
the sealing operation, and consists of installing a valve (23), that allows
periodic checking of
vacuum conditions during operation.
[00123] Figure 25 illustrates an alternative embodiment for making advanced
heat
pipes, those that due to thin walls and special wick structures exhibit
superior thermal transfer
performance, and are easy and inexpensive to manufacture. In Figure 25(a), the
manufacturing
process begins with two thin foils (35) that are first coated with wick
material (18). Because the
wick is formed on a planar surface before the heat pipe is made, the wick
structure can include
different size materials. For example, next to the foil surface, the wick
material can consist of
nano particles in the range of a few nanometers up to 100 nanometers,
depending on the ultimate
vertical length of the heat pipe. In the case of common metals, such as copper
and its alloys, this
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initial layer of nanoparticles is then sintered at temperatures lower than for
conventional HP, of
the order of 500-700 C. In our case it could be several hundred degrees
lower. Alternatively, the
initial layer of nanoparticles can be held in place by an adhesive that can be
subsequently
pyrolized and/or graphitized at temperatures of the order of 800-850 C. Also
they can be
supported by a material that maintains its structure at the temperatures and
vapor pressures used.
For example, it could be 20 nm porous zirconia nanosponges decorated with
nanofilms or
nanoislands of Cu or Ni if water is the working fluid. Next, a second layer of
wick material, such
as particles in the range of 1 to 100 microns, can be deposited on the foil
surface and the process
of sintering or pyrolysis can be repeated, thereby increasing the amount of
mutual attachment.
Alternatively, a second layer of wick material can consist of copper gauze,
which provides a
superior pore structure for the wick. That gauze material can then be joined
with the lower layer
of wick material. Thus, the wick can be built up sequentially to contain
different layers of
different porosity and permeability. Thus, this type of heat pipe can have
lengths up to 10-14 km.
[00124] Once the wick material has been formed onto the foil, a number of
metallic
scaffolds (13) can be placed between the two thin foils (35), so as to form
separate cylindrical
surfaces separated by flat foil surfaces, as illustrated in Figure 25(b). The
foil surfaces that
separate the individual scaffolds should then be sealed by soldering or
crimping, or both. In
Figure 25(b) one end of these cylindrical shapes is closed and sealed by
crimping or soldering, or
both. Partial vacuum is then applied to ensure good contact between the
scaffolding material and
the foil containing the wick layer(s). Ordinarily, such vacuum is sufficient
to provide good
contact between the foil and the scaffold, but subsequent sintering can
effectively weld these
surfaces together. The resulting cylindrical shapes thus become heat pipes (4)
connected by thin
metal foils (35). These can be used as such in applications that require large
surface areas and
effective heat transfer coefficients.
[00125] Figure 25(c) illustrates the option of separating the connected heat
pipe
assembly into individual heat pipes, each having a couple of thin metal flaps
for added surface
area. However, such foil surfaces can be trimmed or cut away, as shown in
Figures 25(d), to
ultimately make individual heat pipes, as shown in Figure 25(e).
[00126] Figure 26 illustrates an optional configuration for transferring
large amounts
of heat over long distances, particularly at depth or in vertical
arrangements. In Figure 26, the
34
heat pipe (4) consists of a "pulsed" heat pipe (See, "An Introduction to
Pulsating Heat Pipes."
Electronics Cooling Magazine.
In figure 26, heat is delivered at one end of the
heat pipe (4) by any source of heat energy. The heat pipe (4) is partially
filled with a liquid fluid
(45) that evaporates as vapor (46) when heat is absorbed by the heat pipe. The
vapor (46)
increases the internal pressure of the heat pipe and causes both vapor (e.g.,
steam bubbles) and
liquid plugs (e.g., slugs) to move in one direction, because a one-directional
valve (47) prevents
flow in the other direction. The internal flow of vapor and liquid transports
heat by mass transfer
to the other extreme of the heat pipe assembly which is at a lower
temperature. This heat transfer
causes heat to be released by condensation of vapor to liquid (the release of
the latent/sensible
heat contained in the liquid phase). As heat is transferred, additional vapor
is condensed into
liquid phase and that liquid continues to flow in response to the pressure
pulses.
[00127] What distinguishes the present invention from conventional pulsating
heat
pipes is that the heat pipe can be manufactured according to the principles
noted in the previous
discussion regarding long-distance heat pipes in Figures 20 through 22, except
that the
reinforcing screens (13) would be placed external to the metal foil (17), so
as to provide strength
to resist the internal pressure pulses, and the lack of a need for an internal
wick material (18).
Alternatively, pulsating heat pipes can be assembled using conventional
methods of joining
pipes. Additional distinguishing features include the use of specialty
coatings on the inner surface
of the heat pipe to promote evaporation and boiling, and/or on the outside of
the heat pipe to
enhance heat transfer to a geologic formation or other heat requiring
application. In addition, the
external surface of the pulsed heat pipe can be thermally insulated, except at
the ends. Thus, this
type of heat pipe can have lengths up to 10-14 km.
[00128] Effective heat transfer that occurs without significant temperature
loss is also
attractive for thermal power plants that have substantial volumes of waste
heat available, but at
temperatures that are normally too low for various industrial applications.
However, a novel
technology has been developed by Sylvan Source, Inc, (US Patent No. 8,771.477,
and patent
application No PCT/US2012/054221, with international filing date of 7
September of 2012, and
priority date of 9 September of 2011, that
can
Date Recue/Date Received 2022-01-26
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purify a broad range of contaminated waters using very little heat energy, and
that technology can
be combined with heat capture to provide useful heat capture with water
purification.
[00129] However, for such innovation to be effective the capture of heat, its
transport
to where it can be used, and its subsequent delivery must take effect with a
minimum of
temperature loses. Heat pipes, thermosyphons, and pulsating heat pipes provide
a practical
solution, provided that the heat pipe system can fulfill all three functions
simultaneously and
without intermediate steps. Thus, there is a need for long-distance heat pipes
that can capture
low-grade as well as higher temperature heat, transfer such heat energy to a
larger diameter heat
pipe with no temperature loss, and deliver such heat energy to a number of
smaller diameter heat
pipes for actual utilization, again not suffering significant temperature
loss. One way in which
this can be accomplished is by having a number of smaller diameter heat pipes
(4) seamlessly
connected to a larger diameter heat pipe (58), and in turn connected to a heat
delivery system
consisting of smaller diameter heat pipes (4), as illustrated in Figure 1.
[00130] Clearly, for a complex heat pipe to function as a single unit it is
essential that
the mechanism for returning the working fluid to the hot end of the heat pipe
must not be
interrupted. That means that the internal wick that functions by capillary
action must be inter-
connected throughout the various joints between the heat pipe elements. Since
joining metallic
heat pipes would normally be accomplished by welding the external
encapsulating material and
such welding cannot be used to join the sintered wick, the question becomes
"how to provide for
capillary continuity" when joining dissimilar heat pipes. Figure 27
illustrates a method to
accomplish this purpose.
[00131] Figure 27(a) shows how to join two heat pipes (4) and (58) of
different
diameter. A hole is cut into the larger heat pipe (58) so that the smaller
heat pipe (4) can fit
precisely. A doughnut-shaped gel (48) containing particles of the same size as
the wick material
is placed at the end of the smaller heat pipe (4), as shown in Figure 27(b),
and the two heat pipes
are joined as shown in Figure 27(c). Figure 27(d) shows an enlarged cross-
sectional view of the
two heat pipes and the gaps that exist in the wick material. Figure 27(e)
illustrates what happens
when solder (49) or a weld is applied to the external surfaces of the two
joined heat pipes: the gel
material liquefies and evaporates, but not completely, thus allowing capillary
action to draw in
the suspension of microscopic particles so as to fill the gaps in capillary
material (12). The heat
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of soldering or welding is sufficient to evaporate all of the liquid used to
suspend the microscopic
particles, leaving behind small funicular rings that can pyrolyze, thus
holding the new wick
particles together (50). as shown in Figure 27(t). Additional heat can then be
applied, if needed,
in order to sinter the additional wick particles together. And of course, all
of the above requires
that there is no vacuum at the time the heat pipes are being joined. An
example of a gel that
could perform as indicated is a silica gel, which would leave welding spots
between the new
wick material consisting of silica--a hydrophilic substance that would
facilitate capillary
continuity. However, the silica would likely dissolve and move from the hot to
the cold side of
the heat pipe, so a preferred material would be a silica gel that has alumina
particles, zirconia or
rare earth particles in suspension, so they permanently weld the wick
together.
[00132] Another important feature of an advanced heat pipe, particularly one
that
integrates several small diameter and large diameter heat pipes, is the
ability to stop the transfer
of heat at will, such as in industrial situations where the main plant must be
disconnected from
the heat transfer mechanism. Figure 28 illustrates one mechanism of
controlling heat transfer in
an advanced, complex heat pipe. As shown in Figure 28(a) a simple valve (60)
that can be
electronically or remotely controlled is attached to the inside of the large
diameter heat pipe (58)
and, while valve (60) is open, the heat pipe continues to transfer heat as
designed. Figure 28(b)
illustrates what happens if the valve closes in response to an external
actuator: the flow of
gaseous working fluid stops entering the small diameter heat pipe (4) and thus
heat transfer is
interrupted.
[00133] An optional configuration of advanced heat pipes includes hybrids of
heat
pipes with pulsating heat pipes and/ or loop heat pipes that combine the best
features of each type
of heat pipe into a single entity with superior performance. For example, a
combination of a
pulsating heat pipe can provide for optimum heat capture and release, while a
standard or loop
heat pipe that is an integral element provides for optimum heat transfer. Such
a hybrid can
include thin wall thickness at the heat capture and release ends, and thicker
walls with or without
thermal insulation to prevent long-distance losses, and a common wick material
that ensures
continuous fluid communication inside the hybrid pipe due to capillary action.
Furthermore, the
capillary wick can consist of an axial or spirally wound wick that
periodically touches the
internal wall, thus maintaining capillary continuity throughout the length of
the heat pipe. Such
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flexible wick can be used to join different heat pipes prior to welding, thus
also maintaining
capillary continuity. Alternatively, the wick material can be grooved for the
long-distance section
of the heat pipe, thus providing for different wick structures that optimize
each function of the
heat pipe: heat capture, transfer, and release. Another option involves the
use of metallic screens
that can weld onto slightly larger or smaller diameter screens that provide
for capillarity.
Heat Release using heat pipes, spreader heat pipes, thermosyphons, and
pulsating heat
pipes
[00134] The release of heat involves the same principles as the capture of
heat, except
that in the case of heat pipes, particularly in conventional heat pipes, the
execution of those
principles are in the reverse order. Thus, releasing heat from a conventional
heat pipe involves
first the condensation of the internal vapor at the cold end of the heat pipe,
then the transfer of
that heat via thermal conductivity through the wick material and subsequently
through the
encapsulating tube which is normally a metal or alloy, and ultimately the
dissipation of that heat
to the medium outside the heat pipe. In the case of advanced heat pipes which
may contain
multiple wick layers of different porosities, the thermal conductivity will
depend on the thickness
of each wick layer and the thermal conductance of the wick material. In the
case of pulsating heat
pipes and thermosyphons, when there is no wick, the thermal conductivity
through the
encapsulating tube will depend on whether the internal fluid is in liquid or
gaseous form, as well
as the thermal conductance of the tube and its thickness.
[00135] The numerous possible configurations described in the previous
paragraphs
have distinct advantages for releasing heat efficiently, such as:
= The use of thinner wall thickness in the encapsulating material for heat
pipes
minimizes temperature loss while enhancing the amount of heat being
transferred
per unit of surface area, as illustrated in figures 17. 20, 22, and 25.
= The use of thin foils as illustrated in figure 25 allows the simultaneous
manufacture
of thin fin structures that enhance the surface area and maximize heat
release.
= The ability to join multiple sections of a complex heat pipe while
maintaining wick
consistency and continuity, allows the capture of heat from different places,
the
transfer of such heat over short or long distances using a larger, more
efficient heat
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pipe, and the delivery of such heat to multiple places by means of smaller
heat
pipes.
= The control features of an on/off switch in heat pipes that allows one to
interrupt or
to maintain the flow of heat at will.
= The use of special configuration heat pipes, such as pulsating heat
pipes, that permit
the vertical or horizontal transfer of heat over very long distances.
= The use of different encapsulating materials for the ends and the middle
of heat
pipes that optimize heat capture and release, while minimizing heat losses
during
heat transfer by means of connecting materials having low thermal
conductivity, or
insulating coatings on the outside of the heat pipes.
= The possible integration of heat pipes with heat storage systems that
provide for
operational flexibility in industrial plants.
All of these contribute to superior thermal characteristics.
[00136] The ability of capturing, transferring, and releasing heat more
efficiently than
heat exchangers, or the so called "economizers" that rely of thermal fluids,
or quenching
operations based on water sprays confers distinct advantages to the heat pipes
described in
previous paragraphs in multiple industrial applications, such as:
= In water purification and, in particular, in desalination of seawater,
purification of
brackish water, purification of ultra-saline aqueous waste from oil and gas
extraction, chemical or metallurgical processes, pulp and paper industries,
and
plastic and rubber operations, to name a few. In effect, the low temperature
differential afforded by heat pipes permits the use of more effective multiple
evaporators in distillation systems, and the superior heat transfer of heat
pipes
enhances thermal performance. Furthermore, water purification configurations
can
include multiple designs, such as vertically arranged stacks, laterally
arranged
distillation systems, or hybrid configurations that fall under the category of
"distillation cores."
39
CA 02959058 2017-02-22
WO 2016/033071 PCT/US2015/046737
= In chemical and petrochemical processing that require either effective
cooling of
exothermic reactions, maintaining of reaction temperatures within a narrow
range,
refrigerating of vessels for synthesis or catalytic reactions at low
temperatures.
= In power plants, nuclear plants, and similar industries that require
effective
cooling, such as by the replacement of cooling towers and other cooling
systems
with highly effective heat pipe driven condenser vessels. Conversely, in using
the
heat release features of heat pipes for pre-heating process vessels, or
controlling
the temperature of flue gases. And particularly in the recovery of low-grade
heat
from flue gases using aero-dynamically shaped heat pipes that may also be
inclined from orthogonal angles in order to reduce drag.
= In metallurgical operations that generate heat intermittently, such as
steel and non-
ferrous plants, or that require controlling temperature as in metallurgical
digestion
processes such as in the Bayer process.
= In the efficient transfer and release of large heat energies, as in
enhanced oil
recovery, oil and gas fracking operations, gas hub operations that recover
heat
from compressors, oil refineries (e.g., distillation towers, coker operation,
and
cooling towers), geothermal energy production, and metallurgical and chemical
operations.
= In miscellaneous applications, such as food and beverage processing.
= And especially in military operations that generate large amounts of
waste heat
while requiring potable water obtained from contaminated sources.
[00137] One skilled in the art will appreciate that these methods and devices
are and
may be adapted to carry out the objects and obtain the ends and advantages
mentioned, as well as
various other advantages and benefits. The methods, procedures, and devices
described herein
are presently representative of preferred embodiments and are exemplary and
are not intended as
limitations on the scope of the invention. Changes therein and other uses will
occur to those
skilled in the art which are encompassed within the spirit of the invention
and are defined by the
scope of the disclosure. For example, an inner wick can be sprinkled inside
the pipe tube and
subsequently sintered at the appropriate temperature, which depends on the
sintered material.
[M138]
[00139] The invention illustratively described herein suitably can be
practiced in the
abs of any element or elements, limitation or limitations which is/are not
specifically disclosed
herein. The terms and expressions which have been employed are used as terms
of description
and not of limitation, and there is no intention that in the use of such terms
and expressions
indicates the exclusion of equivalents of the features shown and described or
portions thereof. It
is recognized that various modifications are possible within the scope of the
invention disclosed.
Thus, it should be understood that although the present invention has been
specifically disclosed
by preferred embodiments and optional features, modification and variation of
the concepts
herein disclosed may be resorted to by those skilled in the art, and that such
modifications and
variations are considered to be within the scope of this invention as defined
by the disclosure.
41
Date Recue/Date Received 2022-01-26
