Note: Descriptions are shown in the official language in which they were submitted.
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Related Application
The present application claims priority from provisional patent application
number
61/851,921, filed March 14, 2013. That filing is incorporated herein by
reference.
Field of the Invention
The present disclosure relates to a new and improved closed loop refrigeration
system
using ice slurries.
Background of the Invention
Refrigeration systems are commonly used to cool an air space, cool equipment,
and to
keep food or perishables at chilled temperatures. Conventional refrigeration
systems typically
consist of three components: a compressor, a condenser and an evaporator, as
well as various
piping, valves and controls that connect all the components. These components
work together
to cycle a refrigerant through the refrigeration system. The compressor
compresses the
refrigerant so that it turns from gas to liquid at a relatively high
temperature. The condenser
then transfers this heat to the atmosphere. The resulting cold liquid
refrigerant is then sent to
the evaporator, which removes the heat from the cabinet or space by turning
the liquid
refrigerant into a gas. That refrigerant gas is returned to the compressor and
the refrigeration
cycle is repeated.
One problem faced with such systems is that the cooling and refrigeration
process requires
large amounts of electrical energy to operate. This places a high demand on
electric utilities
during on-peak periods, usually during waking hours of the weekday. Utilities
must provide
enough generating capacity to meet this demand. Evenings and weekends are off-
peak demand
periods and much less of the total generating capacity is used then. To
encourage a better or more
uniform demand for electric power, many utilities charge a reduced rate for
electricity used
during off-peak periods. Thus, there is an ongoing demand to find ways to
shift or transfer as
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much as possible of required electrical consumption to off-peak periods to
take advantage of the
reduced rates.
One method that is known in the field of refrigeration systems is the use of
an ice slurry
(see, e.g., U.S. 4,584,843). Specifically, known methods for refrigeration in
a process where an
aqueous liquid is fed through a freeze exchanger in indirect heat exchange
with a refrigerant to
convert at least part of the aqueous liquid to ice. Such methods further
include feeding the
aqueous liquid-ice mixture from the freeze exchanger to an ice storage tank to
provide an ice
slurry and aqueous liquid therein, and removing cold aqueous liquid from the
ice storage tank for
feeding through a heat exchanger in indirect heat exchange with a fluid to be
cooled and used for
cooling purposes, with the now warmed aqueous liquid exiting from the heat
exchanger and
returning to the ice storage tank to be cooled by contact with the ice
therein.
Existing approaches, however, each run into one or more system or processing
limitations
which make them unacceptable for certain existing refrigeration applications.
For instance, in
certain processing applications, an excess of ice can have an adverse impact
on the operation of
the system, e.g., due to agglomeration and clogging. Alternative systems
provide for the use of
other refrigerants which have adverse environmental impacts (e.g., due to
unavoidable leakage
over time) as well as undue costs (e.g., due to the high volume of refrigerant
and the cost of
replacement involved). Thus, there is a need for an improved refrigeration
system to reduce
these shortcomings.
Definition of Terms
The following terms are used in the claims of the patent as filed and are
intended to have
their broadest plain and ordinary meaning consistent with the requirements of
the law.
An ice slurry mixture means "a phase changing refrigerant." A multicomponent
ice slurry
mixture means "a phase changing refrigerant including micro-crystals formed
and suspended
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within a solution of water and a freezing point depressant." Slurry ice has
greater heat absorption
compared with single phase refrigerants because the melting enthalpy (latent
heat) of the ice is
also used.
A freezing point depressant means "a solute to water which decreases the
freezing point
of the water, such as ethylene glycol, propylene glycol, various alcohols
(Isobutyl, ethanol), salts
(CaC12, NaC1) and sugar (sucrose, glucose)."
A closed loop refrigeration system means "a refrigeration system in which the
coolant
may be recycled continuously."
A heat load means "the amount of heat entering the area to be controlled by
the
refrigeration system."
An agitator means "an apparatus for mixing a liquid or liquid solid mixture."
Where alternative meanings are possible, the broadest meaning is intended. All
words
used in the claims set forth below are intended to be used in the normal,
customary usage of
grammar and the English language.
Objects and Summary of the Invention
Itis herein provided a new and improved closed loop refrigeration system that
uses ice
slurries.
In one aspect, a closed loop refrigeration system comprises an ice slurry
mixture
which comprises ice, water, and a freezing point depressant. The system also
comprises a first
storage device for storing the ice slurry mixture, and an agitator disposed in
the first storage
device. The agitator agitates the ice slurry mixture in at least an
intermittent manner. The
system further comprises a first conduit connecting the first storage device
and a heat load,
and a first pump disposed on the first conduit for pumping the ice slurry
mixture through the
first conduit from the first storage device to the heat load. At least some of
the ice melts in the
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heat load. The system also comprises a second conduit connecting the heat load
and a second
storage device. The second storage device is connected to the first storage
device. The system
further comprises a second pump disposed on the second conduit for pumping the
ice slurry
mixture containing the melted ice through the second conduit from the heat
load to the second
storage device.
In another aspect, a closed loop refrigeration system comprises an ice slurry
mixture
which comprises about 5 - 60% ice, about 20 ¨ 95% water, and about 0- 50 % a
freezing point
depressant. The system also comprises a first storage device for storing the
ice slurry mixture,
and an agitator disposed in the first storage device. The agitator agitates
the ice slurry mixture
in at least an intermittent manner. The system further comprises a heat load,
a first transporter
for transporting the ice slurry mixture from the first storage device to the
heat load, and a
second transporter for transporting the ice slurry mixture from the heat load
to a second
storage device. The second storage device is connected to the first storage
device.
In a further aspect, a method comprises providing an ice slurry mixture
comprising
about 5 - 60% ice, about 20 ¨95% water, and about 0¨ 50 % a freezing point
depressant in a
first storage device, and agitating the ice slurry mixture stored in the first
storage device in at
least an intermittent manner. The method also comprises pumping the ice slurry
mixture
through a first conduit from the first storage device to a heat load. At least
some of the ice
melts in the heat load. The method also comprises pumping the ice slurry
mixture containing
the melted ice through a second conduit from the heat load to a second storage
device.
It should be noted that not every embodiment of the claimed invention will
accomplish
each of the objects of the invention set forth above. In addition, further
objects of the invention
will become apparent based the summary of the invention, the detailed
description of preferred
embodiments, and as illustrated in the accompanying drawings. Such objects,
features, and
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advantages of the present invention will become more apparent in light of the
following detailed
description of a best mode embodiment thereof, and as illustrated in the
accompanying drawings.
Brief Description of the Drawings
Figure 1 shows a system schematic of a preferred embodiment of a configuration
of a
closed loop refrigeration system operating in accord with the present
invention during off peak
power consumption hours.
Figure 2 shows a system schematic of a preferred embodiment of a configuration
of a
closed loop refrigeration system operating in accord with the present
invention during peak power
consumption hours.
Figures 3 a-b show cross sectional views of a standard elbow and a lead in
chamfer elbow, respectively, with the chamfered lead in reducing steps in the
ID size of
the flow path for a conduit section in accord with the present invention.
Figure 4 shows a system schematic of another preferred embodiment of a
configuration of
a closed loop refrigeration system operating in accord with the present
invention during peak
power consumption hours.
Figure 5 shows a system schematic of a preferred embodiment of a configuration
of a
closed loop refrigeration system operating in accord with the present
invention during off peak
power consumption hours.
Figure 6 shows an example thermocouple engagement for monitoring operation of
a
section of conduit during operation in accord with the present invention.
Detailed Description of the Preferred Embodiments of the Invention
Set forth below is a description of what is currently believed to be the
preferred
embodiment or best examples of the invention claimed. Future and present
alternatives and
modifications to this preferred embodiment are contemplated. Any alternatives
or modifications
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which make insubstantial changes in function, in purpose, in structure or in
result are intended to
be covered by the claims in this patent.
Practically all modern refrigeration systems are closed loop, meaning that the
refrigerant is enclosed (as opposed to being purposefully vented into the
atmosphere) in the
system and thus must fill all the coils and piping. A typical supermarket has
3,000 ¨4,000
pounds of refrigerant in all its various refrigerated display cases, walk-in
coolers, etc. Despite
all precautions, some refrigerant inevitably leaks from the system, causing
environmental
damage and incurring substantial maintenance and repair expenses as well as
the high cost of
replacement refrigerant. For example, some synthetic refrigerants cost
hundreds of dollars per
pound, and refrigeration systems may lose up to 30 ¨40 % of its refrigerants
in a single year.
The same issues apply to refrigeration systems used in home and auto air
conditioners, which
often need service and refilling.
Typical known refrigerants include water, ice, hydrocarbons, propane, butane,
ammonia, chlorofluorocarbons, freon, hydrochlorofluorocarbon,
hydrofluorocarbon, methyl
formate, methyl chloride, sulfur dioxide, etc. Some of these refrigerants such
as water and ice
were found to be problematic, in part because ice tends to agglomerate and
clog the
refrigeration system. Furthermore, ice refrigeration systems can be quite
expensive.
Additionally, a number of these refrigerants were found to be harmful when
leaked
into the environment (e.g., toxic, ozone depletion, global warming, etc.). To
help reduce the
volume of environmentally unfriendly refrigerants used (and leaked to the
environment),
secondary loop refrigeration systems were designed. A secondary loop
refrigeration system
has two refrigeration circuits: a primary refrigeration circuit and a
secondary refrigeration
circuit. Consequently, a secondary loop refrigeration system incorporates two
different
refrigerants to provide cooling: a primary refrigerant in the primary
refrigeration circuit and a
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secondary refrigerant in the secondary refrigeration circuit.
In a secondary loop refrigeration system, one circuit is used to cool the
other circuit
(which is used to cool the target air space or equipment). Thus, there may be
multiple
compressors and heat exchangers that link the two circuits. The configuration
of secondary
loop refrigeration systems is subject to various designs as known in the art.
Typically, the
primary refrigeration circuit remains in a machine room and is used to cool
the secondary
refrigeration circuit (which is used to cool the target air space such as the
supermarket
refrigerator or industrial equipment, etc.)
By using the primary refrigerant to cool the secondary refrigerant, the
overall volume
of the refrigerant needed to cool a target space is reduced compared to a
conventional
refrigeration system.
The primary refrigerant may be a synthetic or natural chemical.
The secondary refrigerant may be water when used above its freezing point.
Many
cooling functions require temperatures close to or below the freezing point of
water, in which
case substances are added to water to lower its freezing point, much like anti-
freeze in an
automobile. Sodium chloride, calcium chloride, low carbon glycols, such as
ethylene glycol,
propylene glycol, butylene glycol and polyglycols thereof, and alcohol are all
examples of
freezing point depressants that can be used in circulating water-based cooling
solutions.
However, salt solutions can be corrosive and glycol solutions may have
increased viscosity if
the concentration of glycol is high.
Carbon dioxide can also be used as a secondary refrigerant. However, carbon
dioxide
systems operate at higher pressures than other refrigerants, which demands
special piping and
fittings.
Brine (salt-based) or water solution refrigerants in secondary loop systems
operate at
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relatively low pressures, but still require substantial pumps, valves and
piping.
As such, both known conventional and secondary loop refrigeration systems have
a
number of shortcomings (i.e., refrigerant harmful to environment, excess
refrigerant needed,
substantial piping, etc.). Thus, there is a need for an improved refrigeration
system to reduce
these shortcomings.
It has been discovered that the use of ice slurries in a closed loop
refrigeration system
reduces many of the shortcomings found in current conventional refrigeration
systems and
current secondary loop refrigeration systems.
Figure 1 shows a closed loop refrigeration system 10 according to one
embodiment of
the present invention that uses an ice slurry which comprises ice, water and
propylene glycol.
There is also present an ice slurry generator or ice maker 1 2 for generating
the ice slurry.
A storage device 14 is provided for storing the ice slurry. The storage device
includes an
agitator 16 that agitates the ice slurry in an intermittent matter to prevent
agglomeration. The
agitation of the slurry can be further aided by the use of a mixer 18 which is
also used to receive
slurry supply from the storage device 14 for mixing with warmer ice slurry
returning from the
heat load 26. Additionally, a peristaltic pump 20 is used to pump the ice
slurry from the ice
slurry generator along a first conduit 22 to the storage device and/or along a
second conduit 24
to a heat load 26. At least some of the ice melts in the heat load. A
vibration motor (not
shown) is used for vibrating said first and/or second conduit to help prevent
the ice from
agglomerating. In addition, a second pump 28 is used to pump the ice slurry
from the heat
load (thus containing melted ice) along a third conduit 30 to the ice slurry
generator for
regenerating the ice slurry in mixer 18 or in melt storage device 32,
depending upon the system
demands (e.g., heat load 26 demands or whether operation is occurring peak
electricity hours).
As shown in Figure 2, an embodiment of the present invention provides for
interruption,
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decrease or stoppage of the ice maker 12 to accommodate for load demands
(e.g., to decrease ice
maker usage during more expensive electricity hours). In such an instance, the
continuing
generation of the ice slurry is provided by the extra ice slurry previously
generated and stored in
the storage device 14, which is combined with the warmed ice slurry returning
from the heat load
26. In this manner, it can be observed that the closed loop configurations
system can maintain a
ice slurry supply for heat load 26 in the absence of the constant operation of
ice maker 12. Of
course, those of ordinary skill will understand that this operation will also
permit a reduced, as
opposed to a stopped operation of the ice make 12 so as to lessen (rather than
stopping) the draw
of electricity during peak hours.
This closed loop refrigeration system according to one embodiment of the
present
invention can be employed in a secondary loop refrigeration system as the
secondary circuit.
The various elements of the embodiments of the invention will be described in
more detail
below.
Ice Slurries
Ice slurries are a type of phase change material that can transfer heat. A
phase change
occurs when ice melts, water boils or wax melts. Ittakes energy to cause such
a change,
called the heat of fusion or the heat of vaporization. 144 BTU/lb is required
to melt ice as
compared to 1 BTU/lb per degree Fahrenheit of so-called sensible heat for
water. (Sensible
heat is the amount of heat that is added or lost by a substance due to a
change in temperature.)
Thus, ice has a superior thermal capacity compared to water.
Since it is difficult to circulate pure ice, it has been discovered that ice
in the form of
an ice slurry can be circulated through a refrigeration system. However, it
has been found that
the ice slurry comprises small, smooth ice crystals that are capable of
flowing in a slurry
through very small tubes; otherwise, it will aggregate easily and prevent
circulation at high ice
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loading. Acceptable ice slurries include those described in U.S. Patent Nos.
6,244,052;
6,413,444; 6,547,811; 7,389,653; 7,422,601; and U.S. Patent Publication Nos.
2009/0125087;
2009-0255276, all of which are herein incorporated by reference.
Ice slurries may also be generated using any conventional ice slurry generator
known
in the art, including the Lanikai frozen drink machine or other scraped
surface heat exchangers..
Ice slurries (or ice slurry mixture) used in one embodiment of the present
invention
comprise a mixture of ice, water and propylene glycol. In one example, ice can
be present in
an amount up to 60% (e.g., ice loadings of 20-30%, 30- 40%, 40-50%, 50-60%,
etc.). In
another example, propylene glycol can be present in an amount up to 50%, and
preferably
no more than 50% or whatever is the eutectic composition of the freezing
point depressdant. (The eutectic point is that temperature and composition
at which a mixture freezes without separation into two phases.) In a further
example, water is present in the remaining amount (e.g., 40%, 50%, 60%, etc.).
In one embodiment, the ice is first formed as small, smooth crystals and
stored as a
concentrated slurry (e.g., 40-60% ice loading) that is too thick to circulate
by itself. When
ready for use, the stored concentrated ice slurry is diluted to about 20-30 %
ice loading at the
appropriate temperature by mixing with another medium (e.g., a return melted
slurry).
Experiments have shown that slurries with 20 % ice loading have approximately
the
same viscosity as pure water at the same temperature, but yet have enhanced
heat transfer
coefficients. As such, high ice loading is desirable to maximize the thermal
capacity of the
ice slurry. Slurries of 20 ¨35 % ice loading have been found to circulate well
while
providing good thermal capacity. In use, all the ice eventually melts and the
solution warms
slightly, adding some sensible heat to the heat of fusion.
The use of an ice slurry refrigerant in a closed loop refrigeration system is
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environmentally friendly than refrigerants used in a conventional
refrigeration system.
Additionally, using an ice slurry refrigerant in a closed loop refrigeration
system uses fewer
parts and is simpler to control than a conventional refrigeration system.
Additionally, combined with the lower flow required for a given heat load, the
use of'
an ice slurry refrigerant in a secondary loop system has lower capital,
maintenance and
operating costs than does a brine or carbon dioxide system.
Components
The concentrated ice slurry is stored in a storage device 14, which may be any
conventional storage container known in the art. The storage device includes
an agitator 16,
which can be any conventional mixing device known in the art. During storage,
intermittent
gentle agitation is applied to prevent aggregation of ice crystals.
A peristaltic pump 20 can be used to pump the ice slurry from the ice slurry
generator
along a first conduit 22 to the storage device. A peristaltic pump or
progressing cavity pump
28 can also be used to pump the ice slurry along a second conduit to a heat
load. It has been
discovered that the "pulsing" action of peristaltic pump (as opposed to a
centrifugal pump)
helps to prevent the ice in the ice slurries from aggregating and clogging the
conduits.
In addition, it has also been discovered that using a vibration motor along
the
conduits can also help prevent the ice in the ice slurries from agglomerating
and clogging the
conduits. This is especially true when using vibration to promote flow of the
concentrated ice
slurry from the storage device.
Any conventional conduits known in the art can be used with the various
embodiments
of the present invention.
The heat load represents any device in which the target air space is being
cooled (e.g.,
refrigerator or jacketed vessel, etc.). At least some of the ice in the ice
slurry will melt in the
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heat load.
Any conventional pumps known in the art (or a peristaltic pump) can be used to
pump
the ice slurry from the heat load (thus containing melted ice) along a third
conduit to the ice
slurry generator for regenerating the ice slurry.
Modes
Furthermore, the advantage of reduction in energy when using the embodiments
of the
present invention can be realized by operating the disclosed technology in
different modes
(i.e., by coordinating the power requirements of the refrigeration system with
the different
electricity rates charged during the day and night). For example, the power
requirements of
the refrigeration system can be operated in accordance with the daily
fluctuations in energy
prices (i.e., off peak vs. peak rates).
Energy is needed to power the compressors in a refrigeration cycle that
produces cold
temperature. The cost of electricity in most places is a function of demand
because electricity
suppliers and utilities have a variety of sources, which have a range of
efficiencies and costs.
The largest and most efficient power plants - coal, nuclear or gas heated, are
used to supply
the base load, while smaller more flexible peak shaving units are employed
when demand
exceeds base load. Utilities typically price electricity to penalize use at
peak times (i.e.,
daytime) and motivate use at off-peak times (i.e., evening). Sometimes the
difference between
night and day, or peak and off-peak, rates can be a factor of two.
To take advantage of the lower off-peak rates, it is advantageous to operate
the
refrigeration compressors in the present disclosure only when rates are low,
and storing the cold
temperature. Making ice is one way to store the cold temperature and is used
in ice-making
units, where water is typically frozen around metal coils filled with
refrigerant. The cold
temperature is recovered when needed by circulating water past the coils,
melting the ice and
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cooling the water, which then circulates as a heat transfer medium to where it
is needed (i.e., air
coolers, heat exchangers or process chillers).
Examples
By way of illustration, the present disclosure will be described in more
detail in the
drawings, photos and pages that follow. One skilled in the art will realize
that many various
designs are possible under the present disclosure and that these examples are
only illustrative
and not meant to include all such possibilities. In addition to the advantages
discussed above,
these examples also illustrate use of an auger freezer (instead of
conventional freezer), the
absence of size reduction step, the absence of valves to control flow of
slurry, and the absence
of ripening or crystal modification step. One skilled in the art will
appreciate that there are
many other advantages of the present disclosure.
Definitions: ice slush was straight from a Lanikai machine 12. Ice slurry was
processed
with the intent to increase the ability to flow and be pumped. ID: inside
diameter. OD: outside
diameter.
Setup (Materials and Equipment) includes a Lanikai frozen drink machine; a
MasterFlex
peristaltic pump; an Electric drill, 0-550RPM; Variac; a tile saw pump; a
heated water bath;
Coleman coolers (2); thermocouples, T type, Omega 5TC-TT-T-36-72 (8); a
measurement
computing USB -Temp ID:02; a digital thermometer, Digisense ID:428763; a
graduated
cylinder; a stopwatch; a stir rod; and a paint mixer.
Example 1: Night Mode
An aqueous solution of a freezing point depressant, such as propylene glycol
is mixed
in a large container. A Lanikai is filled with the mixed solution until there
is approximately 1
cm of standing solution in the Lanikai holding tank. The fill pump fills the
holding tank up to
the proper level. All three tubes are set in the peristaltic pump heads. The
smaller diameter
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tubing should be on a separate pump from the two larger tubes. The mixed
output tube is
directed at the heat exchanger cooler and the pure ice is sent to the ice
storage cooler. The
heat exchanger cooler is filled with solution and the circulation pump is
turned on. The heat
load source is then turned on and the load pump is heated. Subsequently, the
Lanikai output
valve is opened and all peristaltic pumps are turned on and control knobs
adjusted to desired
settings.
Example 2: Day mode
The tubing from the head #2 (the tubing going to ice storage) on peristaltic
pump # I is
removed. Head # 1 is kept intact. The tubing in ice storage is moved to a
location it will not
touch the mixer, but is adequate enough to extract uniform slurry. The output
nozzle on
Lanikai faceplate is closed. The direction of peristaltic pump #1 is reversed,
and the flow of
peristaltic pump #2 is readjusted to desired thickness.
Example 3: Slush flow control experiments
The closed loop slurry system requires a controlled flow of ice slush
throughout the
system. Initial experiments were performed to evaluate different methods of
ice slush flow
control from the Lanikai frozen drink machine. The following experiments were
performed
with a 10% by volume concentration solution of propylene glycol mixed with tap
water.
The Lanikai machine features a main valve on the front face plate that allows
dispensing of the ice slush. The main valve consists of a sliding cylinder
sealed by o-rings
that can be infinitely adjusted between fully open and fully closed. When
fully opened, the
diameter of the orifice is approximately 1" in diameter. By varying the
position of the valve
and therefore the orifice size, the flow of ice slush can be controlled.
However, the valve
position that generates approximately 300 mL/min output flow was found to jam
and stop
flowing after approximately 2-3 minutes of flow at 300 mL/min through the
orifice. The flow
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rate was found to gradually decrease until flow became essentially zero or
lammed". The ice
slush just inside the outlet of the Lanikai is visible due to the clear front
plate. When a jam
occurs, the ice slush visually appeared to be a high concentration of ice
which likely caused
the stoppage of flow or an "ice jam". The flow can be restarted by opening the
valve and in
effect creating a larger orifice.
The opening below the main valve on the front plate of the Lanikai can be
fitted with a
section of 1" ID rigid tubing, bonded to the opening and then connected to a
piece of 1" ID
flexible tubing. Placing the flexible over the rigid tubing is intended to
increase the ability of
the ice slush to flow by eliminating the step which would otherwise be created
when using
certain standard fluid fitting connectors. Flow through the flexible tubing
can be controlled by
varying the height of the opening and overall length of the tube relative to
the Lanikai and
therefore varying the static fluidic pressure differential and amount of
friction. These two
variables were experimentally adjusted to control the flow rate to
approximately 300 mL/min.
However; the rate was found to slow after several minutes and eventually stop
almost
completely or form an "ice jam" as previously discussed. A vibrator motor was
connected to
the flexible tubing to vibrate the ice slush along the tubing. The vibration
was found to have
two effects: both to increase the flow rate and to increase the consistency of
the output flow
rate over time. An experiment was performed where the Lanikai machine was run
continuously for several hours and the output flow rate measured every 15
minutes. Over the 6
hour period, flow rate ranged between 252 and 292 mL/min. The Lanikai machine
with a
flexible tube was connected and coupled to a vibrator motor as described
aboveThe closed
loop system requires controlled flow of ice slush at various locations.
Depending on the final
closed loop configuration. changing the relative height of the ice slush
output may not always be
feasible or easily controlled. To allow more flexibility in system design, the
ice slush flow can be
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controlled by connecting a peristaltic pump to the outlet spout of the Lanikai
faceplate and then
fully opening the main valve on the Lanikai. A MasterFlex peristaltic pump
(7523-10 drive with
7518- 00 head) with W' OD x 0.375' ID (McMaster 5554K 16) was connected to the
outlet of the
Lanikai via a W'push to connect fitting (McMaster 51055K22) and run
continuously for over an
hour successfully.
In this example, the output of the Lanikai was connected to the peristaltic
pump via the Vi"
tubing and a push to connect connector.
Ice slush flow can also be controlled using a rotating auger similar to a
setup found in a
food processing feeder bin. An auger drive system was prototyped and evaluated
experimentally
by driving the 1" x 17" auger drill bit (Menards 2423429) inside a section of
1" ID rigid PVC
tubing (McMaster 49035K25). With approximately 60% ice concentration, the ice
flow can be
controlled by varying the rotation speed of the auger down to zero RPM which
corresponds to
zero mL/min. If ice concentration drops below a critical value, the ice slush
can flow through the
pipe even with zero auger rotation. The critical value of ice concentration is
dependent in part to
the location of the auger relative to the outlet spout on the Lanikai machine.
When configured
with the auger drive approximately 150 mm below the output spout on the
Lanikai faceplate , the
non-rotating auger can control ice slush flow. The maximum flow created by the
auger is limited
and is less than proportional to theoretical rate calculated by multiplying
the linear speed at which
the helix translates axially through the tube by the cross sectional volume of
the void in the auger.
As a result, the ice slush will be constantly mixed by the helix of the
rotating auger as the ice
slush translates along the tube.
A number of different auger drive and peristaltic pump configurations were
experimentally evaluated. An experiment was performed with with a section of
clear PVC pipe
attached to the Lanikai and the 1" connected to an electric drill. The auger
approximates a
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progressing cavity pump, which could serve in a larger embodiment of the
invention.
In the previously described experiments, ice slush from the Lanikai was found
to
flow well through 1" tubing and pipes provided total flow lengths were limited
to
approximately 500 ¨ 1000 mm and in pathways with less than 1800 of total
directional change.
It was also noted that steps in the ID size of the flow path negatively
impacted the ability of
the ice slush to flow. Standard PVC pipes and connectors create a step in the
ID where the
pipe meets the connector. The step was reduced by creating a lead-in chamfer
as shown in
Figures 3 a-b, such reduction of step being useful for either of the first
conduit 22
or second conduit 24.
Example 4: Closed Loop Experiments
An initial closed loop system configuration was evaluated experimentally. The
system
evaluated featured two ice slush flow control mechanisms (a driven auger and a
peristaltic pump)
as well as a submersible pump. The ice slush from the Lanikai machine was
driven at
approximately 300 mL/min into the storage container. From the storage
container, the ice slush
was pumped into one leg of a wye fitting and then into the simulated heat
load. A submersible
pump was at the bottom of the heat exchanger and pumped the melted slush both
into a flow
control valve and then into other leg of the wye fitting as well as back into
the storage reservoir of
the Lanikai. The Figures 1 and 2 show a schematic view of this setup.
Thermocouples were placed
at different locations along the fluid flow path in the system.
This initial evaluation was started with room temperature fluid in the return
reservoir of
the Lanikai, ice storage as well as the heat exchanger; however, the Lanikai
was allowed to run
and create a -5.5 C ice slush prior to opening the main valve on the Lanikai.
The main valve
was opened at approximately sample 950 in the DAQ record and is evident by the
rapid drop
in Lanikai outlet temperature. Due to limitations in this configuration, no
automated slush
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agitation exists in the ice storage container. Throughout the test, the ice
storage container was
manually agitated using a stirring rod or by spinning a paint mixer at
approximately 100 RPM
near the storage outlet to the peristaltic pump. The drop in temperature at
approximately
sample 1060 in the DAQ record can likely be attributed to the point at which
manual mixing
was increased such that fresh ice slush from the Lanikai had been mixed with
the warmer slush
already in the ice storage container.
Table 1 below shows the temperature versus time plot for the various locations
during
an initial closed loop evaluation from May 12,2012 (non calibrated values
reported). The
variation in the "Out of Heat Exchanger" temperature is a result of the
configuration used to
refill the Lanikai reservoir. The submersible pump used to refill the
reservoir is only turned on
when the reservoir is below a minimum level.
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12MAY2012 Closed Loop Test (Auger to Storage, Peristaltic f rom Storage)
=Lanikai Reservoir -Ambient -Bottom of Storage Container -
Lanikai Outlet Spout
-Into Heat Exchanger -Into Storage -Out of Heat Exchanger
a 15 j- : JL _______
25 r
; I
4,P 4
. E .
= r
& 1
E
=
,=
=
-10 -
=. 900 950 eoo Ely.)11C 1 ifiti L200
Sample (0.5Hz sanwde re(t)
TABLE 1
19 =
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Example 5: Peristaltic Ice Slush Pumping Experiment
An experiment was performed to evaluate the ability of the peristaltic pump to
move ice
slush continuously for several hours. A section of Yz" OD x 0.375" ID tubing
(McMaster 5554K 1
6) was connected to outlet of the Lanikai via a shim section ofl "PVC pipe and
a Yz" NPTF
reducing tee fitting and a Yz" push to connect to Yz" NPTM fitting (McMaster
51 055K22). To
simplify this experiment, the flow circuit was reduced so that the ice slush
was pumped directly
to the "heat load" cooler where a submerged pump pumped the melted ice slush
back to the
Lanikai reservoir.
Flow rate of the slush into the heat exchange cooler was recorded and measured
manually
with a stopwatch and graduated cylinder throughout the test. Temperature was
also monitored via
thermocouple at various locations.At approximately data point 7500 the
peristaltic pump was
turned off in an attempt to create an 'ice jam' at the outlet of the Lanikai.
After 20 minutes, the
peristaltic pump was turned on again with no evidence of irregular ice slush
flow. The heat
exchanger was not fully melting the ice slush and therefore the melted slush
being pumped back
into the Lanikai continued to decrease in temperature. And as a result, ice
slush temperature being
pumped into the heat exchanger also continued to decrease as evident by the
three temperature
traces (RESERVOIR, LANK CLOSE, INTO HEAT EXCH) decreasing between
approximately 0
and 4500. During this time period, the flow rate was measured 5 times and
varied between 140
and 152 mL/min.
At approximately data point 4300, it was noticed that the ice slush in the
flexible tubing
was separated by air pockets making up for approximately 30% of the volume in
the tubing. The
air pockets were likely caused by the ice slush becoming thick (cold) as
discussed previously.
The temperature at the Lanikai outlet when the ice pockets were noticed was -
6.8 C. At this
point, warmer (room temperature) melted ice slush was added to the heat
exchanger and
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therefore raised the temperature of the outlet slush again. Repeating this
test with the same
setup and more closely observing the ice slush flow rate obtained given a
constant peristaltic
pump setting may indicate the temperature at which the ice slush is no longer
able to be
pumped with a given setup. Based on these results, it is reasonable to expect
the coldest
temperature for this setup to be approximately -7 to -8 C.
Table 2 shows the temperatures versus time throughout the test:
Peristaltic Pump from Lanikal Directly {Until Pump Off)
REL'ER STt I COOLS -LANK CLOSE INTO >CAT EnCItflo,V3+4, AFTER HEAT
EAC
35
OWN \MANAAVVI400/44e
?Mt\ kt43/
I5
to
ts
ie
lo
1111
111
' = 1.4,
0 j
/OM %.õ i tiodwil
I -
i
.in
'lamp'. 010.5144
TABLE 2
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Example 6: Ice Slush Auger, Storage and Waring Blender Experiments
Bench testing was performed to evaluate the effect of storing ice slush
overnight. A 48 Qt
(45.4 L) size Colman cooler (Sears 80529711) filled with approximately half
way with ice slush was
stored for approximately 8 hours in the ambient lab environment. The cooler
used incidentally had
four 2" diameter holes in the cover that remained unsealed during the test and
the cooler lid was also
slightly propped open. Some kind of mild agitation will be needed to prevent
icebergs from forming
in the stored slush. Additionally, using an intermittent agitation method
should also be considered to
prevent adding too much energy into stored ice and therefore reducing the
cooling capacity.
Example 7: Closed Loop "Reversible Path In/Out of Storage"
A slightly different system architecture was put together to further improve
the control
over the system and simplify the required components. The main feature of this
architecture
is that the ice slush pathway between one of the peristaltic pumps 20 or 28
and the storage
container 1 4 allows for either forward or reverse ice slush flow depending on
the intended
day or night mode operation. Temperatures throughout the flow loop can be
recorded via
thermocouples placed inside the tubing at various locations. Figures 4 and 5
show a block
diagram of the system flow path in this configuration, as well as the
thermocouple location
and ID numbers.
The thermocouples were placed in the following locations identified by their
location in
the schematics:
23
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Channel 0 - Lanikai Reservoir Tank 32
Channel 1 - Ambient
Channel 2 - Lanikai Output 22
Channel 3 - High Ice 14
Channel 4 - Mixed Output to Heat Load 24
Channel 5 - High Ice Storage 14
Channel 6 - Fill Tube 10
This system was first run in night mode for 2 hrs 45 min, followed by day mode
operation for 1 hr. During night mode, Peristaltic Pump One was set to 100
mL/min such that
the two pump heads combined were pumping 200 mL/min of ice slush from the
Lanikai
machine. The mixing drill with a rectangular mixing head was set to a slow,
constant speed.
At the same time, Peristaltic Pump Two was set to 50 mL/min creating a lower
ice
concentration ice slurry mix flowing into the heat exchanger. At the
transition to day mode
operation, the tubing from Head One on Peristaltic Pump One was removed to
allow free ice
slush flow through that segment.
The main valve of the Lanikai was closed to prevent back flow and Peristaltic
Pump
Two was slowed to 30 mL/min given that the ice concentration of the ice slush
in storage had
decreased slightly due to melting (this was detected by an increase in
thermocouple 44
temperature as well as a visual assessment of the ice slush flowing into the
heat exchanger.
The plot of Table 3 below shows the resulting temperatures from the two modes
of operation.
4
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Closethop "Reversible Path In/Out of Storage"
(2012-06-06)
CHANNB_CCHõ\NNai -CHANNELXHANNELrHANNEL4 -CHANNELS CHANNE L6
....
-z
20 , _
11 iiii
..v i A i
iii
A i
, , ,.
..., , ,
1 = . : rii , , ..,..Th _ _ i ?
,
I ( I 1 i ,
a
E - -
s-
f
I
0 - ' ¨ . f
A* 4
=.:=
i
,
I I
¨
2 .4 ..,
41,
A ...
.6 0 ...
v
.a.=
N
IN .... 5' ....
1-..' 11 I.:1 HI
,.; . .
I,-.
a
N ti NI ' 1.4 1:71
NT
el WI III
MI ...
III trI
milionnwoomoml
Night Mode Day Mode
TABLE 3
The following plot of Tab 1 e 4 shows a close up of the sub-zero temperature
range for the
same experiment:
5
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Closed Loop "Reversible Path In/Out of Storage"
( 2012-06-06)
CHANNEL CHANNEL! CHANNEL2 CHANNEL3CHANNEL 4 Cl-ANNE LSC1-
,ANNEL 0
Cl ' r
i mis
' ,,,, = a- o
1 ---
,
1\1 .
i . . .
. , I
,
; +
.4 ,. i r
I '
I 1
0
1 :
I
. /
-6 r
.. ....
6 < <
... 6 b
i P, $
0 s r..!I o
1.4 Z 1 V
r. p !'
" I nrY
I ______________________________________________________________
I
NtghtMode Daytilode
Table 4
The ice slush temperature flowing into the heat exchanger varied between
approximately -4 C
and -2.6 C throughout the test. Excluding the brief period during the
transition between the two
modes, the ice slush temperature remained constant during the transition to
day mode.
Example 8: Lan ikai Power Consumption
The power characteristics of the Lan ikai machine were characterized with an
off the shelf
,
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"Kill-A-Watt EZ Plug Power Meter." An experiment was conducted where the
Lanikai was
connected to the power meter, filled with room temperature propylene glycol
mix and then turned
on. Cold compressor on the Lanikai machine is controlled via a belt tension
switch that is
coupled to the main drive auger inside the main chamber. As the contents in
the chamber cool,
the ice concentration increases causing the torque on the auger to increase.
When the torque
reaches a certain limit the condenser is switched off. The time period from
initial startup to
when the compressor was first turned off was recorded as well as the
temperature of the
contents at that point. The following table 5 summarizes the findings.
Initial Final
Temperature Corn pressor Temperature
Date ( c ) 'ON' Time ( c ) kWH
6/20/2012 23 50 min -5
6/25/2012 23.5 45min 21 sec -5 0.66
6/26/2012 21.2 40 mm 16 sec -5.2 0.59
Table 5
Both a peristaltic pump and an auger drive were found to successfully control
the flow
of ice slush in the system. Both the peristaltic pump and auger drive appear
to allow precise
flow control; however, the auger requires a certain minimum ice concentration
to maintain
control of the flow rate. Use of the main valve or addition of a gate valve
after the auger
could prevent ice concentrations from dropping below the critical valve.
Additionally, when
an auger drive is used, the vertical distance between the auger and the ice
slush distance
should be considered and minimized where possible to prevent fluid separation
in the ice
slush along the vertical distance.
Example 9: Thermocouple Setup
Figure 6 shows how a thermocouple can be inserted into a section of flexible
tubing
7
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as could be used with conduits such as the first 22 or second 24 conduit.
Create a small 2-4 mm
long slit in the flexible tubing then insert a section of a metal tube with
the tip ground to a
sharp point through the slit in the flexible tubing. Insert the thermocouple
though the
cannula of the metal tube, then pull the section of metal tubing through the
ID of the
flexible tubing.
Thermocouple Calibration. As part of the experimentation described herein, a
three
point calibration was performed as described in Table 6:
Degrees C Digisense Ch 0 Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 Ch 6
Ch 7
Ambient 21.5 23.13 22.95 23.74 22.78 21.19 22.36 22.32 ,
Water &
12.92 13.6 13.66 13.67 13.76 12.76 12.86 12.83
Slurry Mix
Slurry -6.39 -5.25 -5.24 -4.57 -5.19 -6.07 -5.59
-5.73
Bottom of
Location for L anikai Ambient Storage Lanikai Into Out of
Into
12MAY2012 Under Container
Outlet NA Storage Heat Head
Reservoir
Test Table Spout Container Load
Load
Table 6
, The above
description is not intended to limit the meaning of the words used in the
following claims that define the invention. Rather, it is contemplated that
future modifications in
structure, function or result will exist that are not substantial changes and
that all such
insubstantial changes in what is claimed are intended to be covered by the
claims. Likewise, it
will be appreciated by those skilled in the art that various changes,
additions, omissions, and
modifications can be made to the illustrated embodiments without departing
from the spirit of the
present invention. All such modifications and changes are intended to be
covered by the
following claims.
8
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