Note: Descriptions are shown in the official language in which they were submitted.
CA 02770786 2012-03-09
LIQUID HEATING SYSTEM
This invention is in the field of liquid heating equipment, and in particular
a system for
heating varying volumes of liquid to selected temperatures.
BACKGROUND
In many industries a supply of hot water or other hot liquid is required for
an operation
on temporary basis. For example in some hydraulic fracturing operations on
underground petroleum formations, large volumes of hot liquid comprising water
mixed
with various other products such as hydrocarbons, proppants and other
additives are
pumped down a well bore as part of the fracturing process. A continuous flow
of liquid
at a selected temperature for a period of time is required. The amount of
liquid needed,
and the selected temperature can vary from one situation to the next.
Providing portable
equipment that can be readily adapted to heat the required varying flow
volumes of liquid
to the varying selected temperatures is problematic.
Water from streams or ponds is often used, and this water often contains
particulate
matter which leaves sludge and contamination in the equipment used to heat the
water.
In some industries such contamination from one site must be cleaned out of the
equipment so same is not transported to contaminate the next site.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a liquid heating system
that overcomes
problems in the prior art.
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In a first embodiment the present invention provides a liquid heating system
comprising a
plurality of heat exchangers including a first heat exchanger, a final heat
exchanger, and a
plurality of middle heat exchangers. Each heat exchanger comprises a right
heating
chamber having a right input port and a right output port, and a left heating
chamber
having a left input port and a left output port. A heating circuit is
connected to a source
of heated supply fluid, and is configured such that circulating heated supply
fluid through
the heating circuit heats target liquid present in the right and left heating
chambers. The
right and left heating chambers are connected such that target liquid to be
heated flows
into the right input port of the right heating chamber of the first heat
exchanger and
through each right heating chamber to the left heating chamber of the final
heat
exchanger, and then through each left heating chamber and through the left
output port of
the first heat exchanger to a hot liquid discharge.
In a second embodiment the present invention provides a liquid heating system
comprising a plurality of heat exchangers including a first heat exchanger, a
final heat
exchanger, and a plurality of middle heat exchangers. Each heat exchanger
comprises a
right heating chamber having a right input port and a right output port, and a
left heating
chamber having a left input port and a left output port. A heating circuit is
connected to a
source of heated supply fluid, and is configured such that circulating heated
supply fluid
through the heating circuit heats liquid present in the right and left heating
chambers.
The right input port of the first heat exchanger is connected to a source of
target liquid to
be heated, and the right output port of each of the first and middle heat
exchangers is
connected to the right input port of a next successive heat exchanger. The
right input port
of the final heat exchanger is connected to the right output port of a prior
middle heat
exchanger, and the right output port of the final heat exchanger is connected
to the left
input port of the final heat exchanger. The left output port of each of the
final and middle
heat exchangers is connected to the left input port of a next successive heat
exchanger.
The left input port of the first heat exchanger is connected to the left
output port of a prior
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=
middle heat exchanger, and the left output port of the first heat exchanger is
connected to
a hot liquid discharge.
In a third embodiment the present invention provides a heat exchanger
comprising an
outer wall and end walls forming an enclosure. An inner dividing wall extends
across the
enclosure to form right and left heating chambers, the right heating chamber
having a
right input port and a right output port, and the left heating chamber having
a left input
port and a left output port. A heating circuit is adapted to be connected to a
source of
heated supply fluid and configured such that during operation heated supply
fluid
circulates through the outer wall and the inner dividing wall, and configured
such that
circulating heated supply fluid through the heating circuit heats liquid
present in the right
and left heating chambers.
The heat exchanger can be mounted with a fluid heating apparatus on a heating
module
that is portable and easily transported. The fluid heating apparatus can be a
substantially
self-contained combustion type fluid heater that can operate in a remote work
site. In the
system of the present invention each heat exchanger and fluid heating
apparatus adds
about the same amount of energy and temperature rise to the target liquid, and
so operates
efficiently, and minimizes the number of heating modules required.
The number of heating modules required can be calculated and portable
equipment that
can be readily adapted to heat the required varying flow volumes of water to
the varying
selected temperatures can be transported to the work site.
The heating chamber of the heat exchangers are open, without cross conduits or
the like,
and so can be cleaned of foreign material by providing closable cleaning
apertures in
each heating chamber.
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In a fourth embodiment the present invention provides a heat exchanger
apparatus
comprising a heating chamber with an input port and an output port. A water
jacket
substantially encloses the heating chamber, the water jacket having a supply
end
extending substantially along a length of the heating chamber, and a return
end extending
substantially along a length of the heating chamber. A supply manifold extends
along
substantially a length of the supply end of the water jacket, the supply
manifold defining
a supply port adapted for connection to receive supply fluid from a
circulating fluid
heater, and a plurality of supply apertures along a length thereof connecting
an interior of
the supply manifold to an interior of the water jacket. A return manifold
extends along
substantially a length of the return end of the water jacket, the return
manifold defining a
return port adapted for connection to return supply fluid to the circulating
fluid heater and
a plurality of return apertures along a length thereof connecting an interior
of the return
manifold to the interior of the water jacket. A size of the supply apertures
is selected
such that a flow of supply fluid entering the supply port is restricted and
such that
resulting pressure in the supply manifold causes the supply fluid to flow
along the length
of the supply manifold and out through each supply aperture in the supply
manifold, then
through the interior of the water jacket around the heating chamber through a
return
aperture in the return manifold into the return manifold and through the
return port.
DESCRIPTION OF THE DRAWINGS
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. 1 is a top view of an embodiment of a liquid heating system of the
present
invention;
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Fig. 2 is a front view of the embodiment of Fig. 1;
Fig. 3 is a schematic sectional front view of a heat exchanger of the
embodiment of
Fig. 1;
Fig. 4 is a schematic sectional end view of the heat exchanger illustrated in
Fig. 3;
Fig. 5 is an end view of a heating module of the embodiment of Fig. 1
including the
heat exchanger of Fig. 3 and a fluid heating apparatus;
Fig. 6 is a schematic illustration of the operation of a heating system of the
prior art;
Fig. 7 is a schematic sectional view of a heat exchanger apparatus with a
single heating
chamber;
Fig. 8 is a schematic side view of the heat exchanger apparatus of Fig. 7;
Fig. 9 is a schematic view of the manifolds and water jacket of the heat
exchanger
apparatus of Fig. 7;
Fig. 10 is a schematic view of the manifolds and water jacket of a heat
exchanger
apparatus of the prior art.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Figs. 1 and 2 illustrate an embodiment of a liquid heating system 1 of the
present
invention. The liquid heating system I comprises a plurality of heat
exchangers 3
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including a first heat exchanger 3A, a final heat exchanger 3B, and a
plurality of middle
heat exchangers 3C. The heat exchanger 3 is schematically illustrated in Figs.
3 and 4.
Each heat exchanger 3 comprises a right heating chamber 5 having a right input
port 5A
and a right output port 5B, and a left heating chamber 7 having a left input
port 7A and a
left output port 7B. The volume of the right heating chamber 5 is
substantially equal to
the volume of the left heating chamber 7.
The right and left input ports 5A, 7A are located in lower portions of the
corresponding
right and left heating chambers 5, 7 and the right and left output ports 5B,
7B are located
in upper portions of the corresponding right and left heating chambers 5, 7.
Thus cooler
liquid enters the input ports 5A, 7A at the bottom of the chamber where same
is heated as
it passes through the chamber to the output ports 5B, 7B located at the top of
the opposite
end of the chamber. The hottest liquid in the chamber will be at the top of
the chamber
and thus will flow out of the output ports 5B, 7B.
The terms "right" and "left" are used for convenience of reference only to
differentiate
the heating chambers for the purposes of the present description.
A heating circuit 9 is connected to a source of heated supply fluid, and is
configured such
that circulating heated supply fluid 11 through the heating circuit 9 heats
liquid present in
the right and left heating chambers 5, 7. In the illustrated system 1, each
heat exchanger
is mounted on a heating module 13, illustrated in Fig. 5, that includes a
fluid heating
apparatus 15 operative to provide the source of heated supply fluid. The
heating module
13 is portable and easily moved from one job site to the next, and includes
any pumps,
fuel tanks, electrical power systems, and the like necessary to operate,
control, and
circulate the heated supply fluid 11 through the fluid heating apparatus 15
and the heat
exchanger 3. The fluid heating apparatus 15 is typically provided by a
substantially self-
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contained combustion type fluid heater that does not require external
electrical power and
so can be conveniently set up and operated at a remote work site.
The illustrated heat exchanger 3 includes an outer wall 17 and end walls 19
forming an
enclosure, and an inner dividing wall 23 extending across the enclosure to
form the right
and left heating chambers 5, 7, and the heating circuit 9 is configured such
that heated
supply fluid 11 circulates through the outer wall 17 and the inner dividing
wall 23. The
illustrated heating circuit 9 includes a supply input line 25 connected to a
supply
manifold 27 that distributes the heated supply fluid 11 along a length of the
heat
exchanger 3 through manifold holes 29. The heated supply fluid 11 then flows
through a
water jacket 31 around a first side of the outer wall 17, then up the inner
dividing wall 23,
back down the inner dividing wall 23, and up the second side of the outer wall
17 through
a return manifold 28 to the return line 33 and hack to the fluid heating
source 15.
In the system 1 of the present invention the right and left heating chambers
5, 7 are
connected such that the target liquid 35 that is to be heated flows into the
right input port
5A of the right heating chamber 5 of the first heat exchanger 3A and through
each right
heating chamber 5 of the first, middle, and final heat exchangers 3A, 3C, 3B
to the left
heating chamber 7 of the final heat exchanger 3B, and then through each left
heating 7
chamber of the final, middle, and first heat exchangers 3B, 3C, 3A and through
the left
output port 7B of the first heat exchanger 3A to a hot liquid discharge 37.
Direction of
target liquid flow is indicated by arrows between the heat exchangers 3 in
Figs. 3 and 4.
The right input port 5A of the first heat exchanger 3a is connected to a
source 39 of target
liquid 35 to be heated, and then right output ports 5B and right input ports
SA are
connected together such that target liquid 35 flows from the right input port
5A of the
first heat exchanger 3A through each right heating chamber of the first and
middle heat
exchangers 3A, 3C to the right heating chamber 5 of the final heat exchanger
38. The
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right output port 5B of the final heat exchanger 3B is then connected to the
left input port
7A of the final heat exchanger 3B and left output ports 7B and left input
ports 7A are
connected together such that the target liquid 35 flows from the right output
port 5B of
the final heat exchanger 3B through each left heating chamber 7 of the final
and middle
heat exchangers 3B, 3C to the left heating chamber 7 of the first heat
exchanger 3A and
out the output port 78 thereof.
In the system 1 the temperature of the target liquid 35 increases in each
chamber such
that the temperature of the target liquid 35 at the output port 5B or 78 of
any heating
chamber 5, 7 is greater than the temperature thereof at the input port 5A or
7A of that
same heating chamber. Thus since the target liquid 35 flows through all the
right heating
chambers 5 before entering the left heating chamber 7 of the final heat
exchanger 3B and
then flowing through all the left heating chambers 7 in reverse order, it can
be seen that in
each heat exchanger 3 of the system 1, the target liquid 35 in the right
heating chamber 5
1.5 will have a temperature that is lower than the temperature of the
target liquid in the left
heating chamber 7 thereof.
As well, the lowest temperature of the target liquid 35 will be when entering
the system 1
at the input port 5A of the right heating chamber 5 of the first heat
exchanger 3A, with
some temperature increase in each heating chamber between the input and output
ports
thereof until the target liquid 35 exits the system 1 to the hot liquid
discharge 37 at the
maximum temperature achieved.
In the prior art at a typical work site where it is required to heat a target
liquid, as
schematically illustrated in Fig. 6 a number of similar conventional liquid
heating units
113 would be connected together, the number selected to achieve the desired
temperature
increase at the required flow rate. The target liquid 135 enters the first
unit at a first
temperature Ti, and leaves the first unit ,at temperature T2 and enters the
second unit at
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that temperature T2, leaves the second unit at temperature T3 and enters the
third unit at
that temperature T3, leaves the third unit at temperature T4 and enters the
fourth unit at
that temperature T4 and leaves the fourth unit at the desired temperature T5.
It is known that the rate of heat transfer from one liquid or like source to
another liquid or
like target decreases as the temperature gradient between the source and the
target
decreases.
Thus in the conventional system of Fig. 6, in the first conventional liquid
heating unit the
supply fluid will enter the heat exchanger of the unit at a supply temperature
IS, heat will
be absorbed from the supply fluid relatively quickly by the cold target liquid
at
temperature Ti and the supply fluid returns from the heat exchanger 103 to the
fluid
heater 115 at a return temperature TR significantly less than the supply
temperature TS.
Then in the second conventional liquid heating unit, the supply fluid will
again enter the
heat exchanger of the unit at a temperature TS, heat will be absorbed less
quickly by the
target liquid at the higher temperature T2 and the supply liquid returns from
the heat
exchanger 103 to the fluid heater 115 at return temperature TR' that is higher
than the
return temperature TR of the supply fluid in the first unit. Similarly on
through the rest
of the conventional liquid heating units 113, such that in the schematic
illustration of Fig.
6, TR<TR.'<TR"<TR'".
The amount of energy added by each conventional liquid heating unit 113 to the
target
liquid is proportional to the difference between the supply temperature TS and
the return
temperature TR of the unit. Thus each successive conventional liquid heating
unit 113
transfers less energy than the prior unit.
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In contrast in the system I of the present invention, since the volume of the
right and left
heating chambers is substantially the same, the average temperature of the
target liquid
35 in each heat exchanger 3 is the average of the temperature RT of the target
liquid in
the right heating chamber and the temperature LT of the target liquid in the
left heating
chamber.
Thus in the first heat exchanger 3A the temperature RT of the target liquid in
the right
heating chamber 5 that is just entering the system 1 is the coldest of any
heating chamber
in any of the heat exchangers 3, while the temperature LT of the target liquid
in the left
heating chamber 7 that is just leaving the system 1 is the hottest of any
heating chamber
in any of the heat exchangers 3. The average temperature in the first heat
exchanger 3A
is thus (RTA LTA)/2.
In the next in line middle heat exchanger 3C', the temperature RT of the
target liquid in
the right heating chamber 5 is higher than the temperature in the prior right
heating
chamber 5 of the first heat exchanger 3A, and the temperature LT of the target
liquid in
the left heating chamber 5 is lower than the temperature in the subsequent
left heating
chamber 7 of the first heat exchanger 3A, and the average temperature of the
target liquid
in heat exchanger 3C' is about the same as the average temperature of the
target liquid in
first heat exchanger 3A.
This temperature relationship carries on all through the system 1 from one
heat exchanger
to the next. In the final heat exchanger 3B, the temperature RT of the target
liquid in the
right heating chamber 5 is only one temperature step less than temperature LT
of the
target liquid in the left heating chamber 7. The target liquid 35 at this
point is just about
to turn and return along the left heating chambers 7 of the string of heat
exchangers, and
the temperature thereof has increased by about one half of the total increase
required
between the temperature of the target liquid entering the system and the
temperature of
CA 02770786 2012-03-09
the target liquid leaving the system, and is therefore at an average
temperature of about
(RTA + LTA)/2, the same as in the first heat exchanger 3A.
The temperature of the target liquid in each heating chamber 5, 7 will
increase between
the input port and the output port, however generally speaking the above
described
temperature relationship will be present in each heat exchanger 3. Thus the
temperature
gradient between the supply temperature IS of the supply fluid entering each
heat
exchanger 3 and the average temperature of the target fluid in the right and
left heating
chambers 5, 7 of the heat exchanger 3 will be about the same in each heat
exchanger.
The return temperature TR of the supply fluid leaving each heat exchanger and
returning
to the fluid heating source 15 will also be about the same, and so the amount
of energy
added by each heat exchanger 3 and fluid heating source 15 to the target
liquid is about
the same.
With each heat exchanger 3 and fluid heating source 15 adding the same amount
of
energy, the number of heating modules 13 in the system 1 of the invention is
reduced
compared to the number of conventional liquid heating units 113 required,
where each
successive conventional liquid heating unit 113 transfers less energy than the
prior unit.
The heat exchangers of the illustrated system 1 also define cleaning apertures
41 in the
right and left heating chambers 5, 7, and removable covers 43 on the cleaning
apertures.
The heating chambers 5, 7 are open with substantially smooth walls which can
be readily
cleaned of accumulated residue, sludge, sediment, and like particles of
material that can
result from, for example, using unclean water from rivers, ponds, and the like
as is
sometimes desirable in remote work sites.
The cleaning apertures 41 schematically illustrated in Fig. 4 are defined in
the top of the
outer wall 17 but same could also be defined in an end wall 19 as illustrated
in Fig. 3,
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where an upper cleaning aperture 41A and a lower drain aperture 41B in each of
the right
and left heating chambers 5, 7 would facilitate cleaning of foreign material
from the
heating chamber 5, 7.
It is contemplated that 20 ¨ 30 heating modules 13 could be practically
connected in the
system 1 of the present invention to provide a wide range of heating
capacities for a wide
range of water flow volumes and desired target liquid temperatures. The
independent
heating modules are conveniently transported and connected by simple conduits
and
connectors such that assembly at a work site is readily accomplished,
Figs. 7 ¨ 9 schematically illustrate the operation of the water jacket 31 and
manifolds 27,
28 of Fig. 3 in use on a heat exchanger apparatus 203 that has only a single
heating
chamber 205 with an input port 205A and an output port 205B. A water jacket
231
substantially encloses the heating chamber 205. The water jacket 231 will in
some
applications enclose the ends of the heating chamber 205 as well as the walls
thereof, or
in other applications the ends will be covered by an insulating layer. The
illustrated
water jacket 231 has a supply end 231A extending the length L of the heating
chamber
205, and a return end 231B extending the length L of the heating chamber 205,
A supply manifold 227 extends along substantially a length of the supply end
231A of the
water jacket 231. The supply manifold 227 defines a supply port 227A adapted
for
connection to a supply line 225 to receive supply fluid 211 from a circulating
fluid heater
215, and a plurality of supply apertures 229 along a length thereof connecting
an interior
of the supply manifold 227 to an interior of the water jacket 231.
A return manifold 228 extends along substantially a length of the return end
231B of the
water jacket 231. The return manifold defines a return port 228A adapted for
connection
to a return line 233 to return supply fluid 211 to the circulating fluid
heater 215 and a
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plurality of return apertures 230 along a length thereof connecting an
interior of the return
manifold to the interior of the water jacket 231.
The size of the supply apertures 229 is selected such that a flow of supply
fluid 211
entering the supply port 227A is restricted and such that resulting pressure
in the supply
manifold 227 causes the supply fluid 211 to flow along the length of the
supply manifold
227 and out through each supply aperture 229 in the supply manifold, then
around the
heating chamber 205 through one of the return apertures 230 into the return
manifold 228
and through the return port 228A to the return line 233. The supply port 227A
and return
port 228A are located substantially at a mid-point of the length of the
corresponding
supply and return manifolds 227, 228 to provide even fluid flow from each end
of the
manifolds.
The effect of the manifolds 227, 228 on the flow of supply fluid through the
water jacket
231 is schematically illustrated in Fig. 9. The back pressure in the supply
manifold 227
ensures that supply fluid 211 moves down the length of the supply manifold 228
and out
each supply aperture 229, more or less equally through each. The flow of
supply liquid
211 is indicated by the arrows. Because the return manifold 228 on the
opposite end of
the water jacket 231 also has return apertures 230 along the length thereof
the supply
liquid 211 will flow generally from a supply aperture 229 to an opposite
return aperture
230 such that a substantially equal flow of supply fluid 211 is present along
the length of
the water jacket 231 from the supply end 231A thereof to the return end 231B
thereof
The total area of the supply apertures 229 is generally less than a total area
of the return
apertures 230 such that there is little resistance to the flow of supply
liquid 211 into the
return manifold 228. Thus where the number of supply apertures 229 is the same
as the
number of return apertures 230, and where each supply aperture 229 has
substantially the
same area and each return aperture 230 has substantially the same area, and
the area of
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each return aperture 230 will be greater than the area of each supply aperture
230.
Conveniently the return apertures 230 will simply be somewhat larger than the
supply
apertures 229, but the number of apertures 229, 230 could vary and a similar
result
obtained by sizing the apertures accordingly.
This even flow provides an even temperature across the length L of the water
jacket 231,
decreasing from the supply end 231A to the return end 231B as heat is
transferred from
the supply fluid 211 to a target liquid in the heating chamber 205. Thus the
entire area of
the water jacket 231 is substantially at the same temperature gradient and is
exposed to
the heating chamber 205.
Heat transfer from the water jacket 231 to the heating chamber 205 is
increased compared
to a typical prior art water jacket 331 illustrated in Fig. 10, where the
supply fluid 311
enters the water jacket 331 directly through a supply line 325 and leaves
directly through
a return line 333. The supply fluid 311 enters the middle of the supply end
331A of the
water jacket 331 and then moves naturally toward the return line 333 in the
middle of the
opposite return end 331B thereof, generally as indicated by the arrows. As
there are no
inlets or outlets near the outer regions 334 of the water jacket 331 removed
from the
supply line 325 and return line 333, there is little flow of supply liquid 311
in the outer
regions 334 of the water jacket 331. The temperature of the outer regions 334
is
therefore significantly less than the central regions 336 of the water jacket
331 through
which the supply liquid 311 predominantly flows, and heat transfer efficiency
is reduced.
In the heat exchanger apparatus 3 of Figs. 3 and 4 as discussed above the
heating
chamber is divided into a right heating chamber 5 having a right input port 5A
and a right
output port 5B, and a left heating chamber 7 having a left input port 7A and a
left output
port 7B, and the water jacket 31 includes similar supply and return manifolds
27, 28 and
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is configured to heat a target liquid in both the right and left heating
chambers 5, 7 in a
similar even efficient manner.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.
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