Note: Descriptions are shown in the official language in which they were submitted.
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Heat Pump System
This invention relates to a reversible refrigeration system which
is adapted to deliver optimum performance in either a heating or a
cooling mode of operation.
More specifically, this invention relates to a heat pump having
control means associated therewith for automatically routing
refrigerant to each of the heat exchangers in response to the
exchangers' function whereby each exchanger operates efficiently
when called upon to serve either as a condenser or as an
evaporator.
Most air side heat exchangers employed in refrigeration systems are
of the plate fin construction wherein refrigerant is directed
through a number of heat transfer zones via flow circuits running
through the unit. When the exchanger is used as a condenser, the
flow of refrigerant is routed through the circuits so that it
passes in series through each zone. On the other hand, when the
exchanger is used as an evaporator, the refrigerant is generally
routed through each circuit simultaneously to establish a parallel
flow through the circuits. As can be seen, the flow geometry
associated with a well designed condenser is not compatible with
that of a well designed evaporator. -
In a heat pump environment, it has been the usual practice to
compromise the heat exchanger design in order to permit the
exchangers to provide the double duty function required. This, in
turn, limited the performance of the entire system. -
It is therefor an object of the present invention to improve heat
pump systems.
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It is a further object of the present invention to provide a heat
pump system for automatically controlling the flow of refrigerant
through the system whereby the system performs effectively in
either a cooling or a heating mode of operation.
In one aspect of the present invention there is provided in a heat
pump system having a compressor, a pair of heat exchangers and
means for selectively reversing the flow of refrigerant through the
system so that the function of the exchangers is also reversed, the
improvement comprising means for separating each exchanger into a
plurality of heat transfer zones, each zone containing a number of
flow circuits, flow control means for routing refrigerant
discharged from the compressor through each of the zones of one
exchanger in a series flow progression and routing the refrigerant
discharged from said one exchanger into the other exchanger
simultaneously through each of the zones of said other exchanger
whereby flow is parallel through the zones, and switching means
operatively associated with said flow control means for
automatically reversing the flow geometry through the exchangers in
response to reversing the flow of refrigerant through the system
whereby refrigerant flow is parallel through said one exchanger and
in series through said other exchanger.
In a further aspect of the present invention there is provided a
heat pump system having a compressor, an indoor coil, an outdoor
coil, a reversing valve for delivering refrigerant discharged from
the compressor to the indoor coil during heating operations and to
the outdoor coil during cooling operations, the method of
processing refrigerant through the system including the steps
separating the indoor and outdoor coils into a plurality of heat
` transfer zones, each zone having a number of flow circuits passing
through the coil associated therewith, routing the refrigerant
delivered from the compressor to the outdoor coil during the
cooling operations so that refrigerant flows through each of the
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heat transfer zones in a series progression, delivering the
refrigerant discharged from the outdoor coil to each of the heat
transfer zones of the indoor coil simultaneously so that the
refrigerant flows through the zones in a parallel flow, returning
the refrigerant from the indoor coil to the compressor to complete
the cycle, and reversing the flow geometry through the indoor and
outdoor coils in response to a change in the systems operation
whereby refrigerant flows in series through the zones of the indoor
coil and in parallel through the zones of the outdoor coil.
These and other objects of the present invention are attained by
means of a heat pump system having refrigerant flow control means
associated therewith to produce a series flow geometry through the
heat transfer zones of either of the heat exchangers when the
exchanger is serving as a condenser and a parallel flow geometry
through the zones when the exchanger is serving as an evaporator.
For a better understanding of the present invention as well as
other objects and further features thereof, reference is had to the
following detailed descripton of the invention to be read in
connection with the accompany mg drawings, wherein:
Figure 1 is the schematic representation of a reversible
refrigeration system utilizing the heat exchanger of the present ::
invention;
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Figure 2 is a partial perspective view showing a multicircuit heat
exchanger utilizing the teachings of the present invention;
Figure 3 is a partial front view of the heat exchanger shown in
Figure 2;
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Figure 4 is an end view of the heat exchanger shown in Figure 3;
Figure 5 is a schematic representation illustrating the flow
circuits of the exchanger shown in Figures 2 through 4; and
Figure 6 is an enlarged view in section illustrating a capillary
tube feeding one of the flow circuits of the exchange shown in
Figures 2 through 4.
Figure 1 represents the simplest form of the invention being
utilized in a reversible vapor compression system, generally
referenced 10. The system includes a compressor 11 of any suitable
design and two refrigerant heat exchangers 12, 13 which are
typically plate fin coils which are specifically fabricated to
exchange energy between air moving over the plates and refrigerant
moving through the exchanger flow circuits. For purposes of this
description, heat exchanger 12 shall be referred to as the indoor
coil while heat exchanger 13 shall be referred to as the outdoor
coil. The two coils are operatively connected to the compressor by
a four-way valve 15, which enables the discharge vapor from the
compressor to be selectively directed into either one of the
exchangers. When the system is in a cooling mode of operation, the
discharge is carried via line 16 into a primary header 17
dissociated with the outdoor coil. At this time, the suction end
of the compressor is operatively connected to the primary header 33
by means of line 36. By cycling the four-way valve, the flow of
refrigerant through the system is reversed and, accordingly, the
role of the heat exchangers is also reversed.
The operation of the system shall be initially explained with the
system in a cooling mode of operation wherein the outdoor coil 13
is called upon to serve as a condenser. The refrigerant vapor
collected in the primary or upper header 17 flows downwardly
through a refrigerant circuit 19. The refrigerant is caused to
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move through two heat transfer zones, an upper zone A and a lower
Zone B. The two zones are separated by return bend 14 which
functions as an intermediate header for passing refrigerant from
one zone to the other.
After passing through the two heat transfer zones, the refrigerant
enters a lower secondary header 18 associated with the indoor coil.
The lower header 18 is placed in fluid flow communication with
secondary header 31 associated with the indoor coil by means of
liquid line 23. It should also be noted that the lower header 18
is also placed in fluid flow communication with the upper header 17
by line 20 which bypasses the heat exchanger circuit. A check
valve 21 is positioned in the bypass line. The valve is held
closed when the outdoor coil is operating as a condenser by the
pressure difference established over the exchanger as the
refrigerant changes from a vapor to a liquid. As a result, the
liquid refrigerant collected in the lower or secondary header is
prevented from flowing back into the primary header via line 20
when the exchanger is serving as a condenser.
The liquid refrigerant collected in header 18 moves along liquid
line 23 through another check valve 24. Check valve 24 is arranged
to open when the system is in a cooling mode of operation whereby
the liquid refrigerant is directed toward the second indoor coil
12. A second check valve 25 also is positioned in the liquid line
close to the secondary header 31 associated with the indoor coil.
The check valve 25 is arranged to operate in opposition with check
valve 24 whereby the refrigerant is precluded from flowing directly
from the liquid line into header 31. The refrigerant is thus
forced to move into a distributor 27 positioned forward of check
valve 25 in relation to the direction of flow.
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In the distributor, the flow is split into two separate flow paths
by means of a pair of capillary tubes 28, 29. As seen in Figure 1,
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the capillary tubes are passed into centrally located return bend
30 which serves as an intermediate header in regard to the indoor
coil. In practice the capillaries pass through the return bend and
empty deeply into the circuit tubing connected thereto. As a
result, a portion of the refrigerant is expanded into upper heat
transfer zone C and a portion expanded into lower heat transfer
zone D. Because of the pressures involved, a portion of the
refrigerant flows upwardly through the flow circuit 34 into the
primary header 33 and a portion of the refrigerant flows downwardly
into the secondary header 31. As can be seen, the flow geometry of
the indoor coil, which is functioning as an evaporator in the
cooling mode of operation, consists of two distinct flow passages
through which the refrigerant is moved simultaneously, one passage
carrying refrigerant through heat transfer zone C and the other
through heat transfer zone D.
As in the case of the outdoor exchanger, the indoor exchanger also
has a bypass line 34 associated therewith which places the primary
header 33 in fluid flow communication with the secondary header 31.
A check valve 35 is located in the bypass line and is arranged to
open when the exchanger 12 is operating as a condenser. With check
valve 35 open, the two headers 31, 33 are exposed to the suction
side of the compressor by means of line 36 thereby completing the
cycle. -
Changing the system mode of operation, which is accomplished by
cycling the four-way valve, reverses the flow of refrigerant
through the system. This in turn changes the function of the two
exchangers. At this time, the position of the four check valves
changes. Bypass line 20 is thus opened while line 34 is closed.
Similarly check valve 25 opens while check valve 24 closes.
The discharge from the compressor passes via line 36 and header 33
through the indoor coil, which is now acting as a condenser, into
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the lower header 31. The refrigerant, as it moves through the
indoor coil, passes in series through the two heat transfer zones C
and D. From the header 31, the refrigerant moves down the liquid
line toward the outdoor coil. The flow is however blocked by
closed check valve 24 causing the refrigerant to move into
distributor 37 where the flow is split into two paths by means of
capillary tubes 38, 39.
The capillaries pass through the intermediate header or tube bend
14 into the circuits associated with heat transfer zones A and B.
Here again, the flow is split in two directions through the
exchanger with part of the flow directed into secondary header 18
and part into primary header 17. The two headers are connected to
the suction end of the compressor via open bypass line 20 and line
16 to close the heating loop.
As should be clear from the description above, the flow of
refrigerant through the heat exchangers is automatically controlled
so that the flow geometry through each exchanger is changed
depending on whether the exchanger is being used as a condenser or
an evaporator. More specifically, when the heat exchanger is
called upon to serve as a condenser, refrigerant is caused to flow
in series through the exchanger heat zone. By the same token, the
refrigerant is caused to flow simultaneously, or in parallel,
through the heat zones when the exchanger is serving as an
evaporator. In this manner, the performance of the system can be -
optimized for either a heating or cooling mode of operation, a
result heretofore unattainable because of limitations placed upon
the system as a result of the compromise necessitated by heat
exchanger design.
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It should be clear from the description above that the system is
not necessarily limited by the use of headers in connection with
the exchangers when the invention is carried out in connection with
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a simple exchanger. In this regard the header can be replaced with
standard tubing capable of facilitating the movement of refrigerant
into and out of the exchangers.
Similarly, the present invention can be carried out in conjunction
with a complex coil in which a multitude of circuits are passed
back and forth through the exchanger unit. A complex coil, such as
those typically utilized in larger refrigeration systems is
illustrated in Figures 2 through 4. For purposes of explanation,
the coil shall be deemed to be an outdoor coil utilized in a
reversible refrigeration system similar to that described in Figure
1.
A coil of complex circuitry containing a plurality of refrigerant
flow circuits is illustrated in Figures 2 through 4. The coil
includes two vertically aligned rows of finned tubes, an inner row
40 and outer row 41 which extend back and forth through the heat
exchanger. The rows are interconnected by return bends 42 to form
a number of individual refrigerant flow circuits of predetermined
geometry. Typically, the two terminal ends of each circuit are
brought out of the coil assembly through one of the assembly tube
sheets as for example tube sheet 45, so that both the entrance and
discharge opening to each circuit is conveniently located along one
side of the exchanger.
In the complex coil herein described, the coil contains seven flow
circuits that are arranged to pass through three heat transfer
zones. It should become obvious, however, from the discussion
below, that the number of circuits and heat transfer zones may vary
depending upon the capacity of the unit involved and other design -
considerations.
Positioned along the side of the coil adjacent to the tube sheet 45
is a header network adapted to operate in conjunction with two
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check valves to route the flow of refrigerant through the heat
exchanger in a prescribed manner when the exchanger is acting in
the system as a condenser and in a different manner when it is
acting as an evaporator. The header includes a primary header 47,
a dummy or intermediate header 48, a secondary header 49 and a
liquid header 46. It should be noted that the primary and
secondary headers are axially aligned with the interior chambers of
each header being separated by means of a check valve 51. The
lower end of primary header 47 is joined in fluid flow
communication with a compressor line 50 that is operatively
connected to the compressor by means of a four-way valve (not
shown).
When the coil is serving as a condenser, high temperature and
pressure vapor is delivered into the primary header via line 50
thereby causing check valve 51 to close. The closing of the valve
in effect isolates the chamber of header 47 from that of header 49.
The now isolated primary header is thus caused to feed refrigerant
into four flow circuits by means of feeder tubes 52 operatively
associated therewith. The four circuits fed by header 47 are
positioned in the lower section of the coil and make up a first
heat transfer zone, herein referenced zone E.
A simplified schematic illustration of the flow through the heat
exchanger is shown Figure 6. It is believed that the use of the
schematic in conjunction with the drawing of Figures 2 through 4
will help in better understanding the flow geometry through the
exchanger. After passing through the four flow circuits making up
heat transfer zone E, the refrigerant is passed into the dummy
header 48 via discharge lines 53. Because of the pressure
differential involved, the refrigerant moves upwardly through the
dummy header and is discharged into the two uppermost circuits in
the coil by means of feeder tubes 54. The two upper refrigerant
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flow circuits combine to establish a second, smaller heat transfer
region F.
After passing through the coil assembly, the refrigerant from the
two upper circuits is routed to the secondary header 49 via
discharge line 56. The refrigerant is collected in header 49 and
fed into the last flow circuit by means of a single feeder tube 58.
The last circuit passes through the third and final heat transfer
zone, zone G, and is discharged into the liquid header 46.
Preferably, the final heat transfer zone is located in the central
portion of the coil to enhance the heat transfer characteristics of
the coil. For the purposes of clarity, the final heat transfer
zone is illustrated at the top of the heat exchanger assembly.
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The refrigerant, which is now in a liquid phase is collected in the
liquid header 46 and is passed through opened check valve 61 into a
T-connector 62. At the connector, the refrigerant moves down
liquid line 60 toward the indoor coil (not shown).
As can be seen from the description above, the header network,
acting in concert with the check valves, operates to direct the
refrigerant from the compressor through the heat transfer zones in
a series flow progression. Furthermore, the number of flow
circuits in each zone diminishes in the direction of flow. By
zoning the coil in this manner, the flow geometry of the coil is
regulated in response to the increase in density of the fluid to
obtain optimum coil performance when operating as a condenser.
When the systems mode of operation is reversed, the coil's function
is similarly reversed. In the heating mode, liquid refrigerant is
moved along liquid line 60 toward check valve 61. The valve,
however, is automatically moved to a closed position because of the
change in pressure felt over the valve. The refrigerant is thus
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forced to move into distributor 63 that is connected to T-connector
62. At the distributor, the flow is separated into seven flow
paths by means of capillary tubes 65. It should be noted that the
number of capillary tubes are equal in number to the number of flow
circuits passing through the coil.
As best illustrated in Figure 6, six of the capillary tubes pass
through the dummy and pass into feeder tubes 54 associated with the
four circuits contained in heat transfer zone E and the discharge
tubes 53 associated with the two circuits associated with heat
transfer zone F. The capillary tubes extend deeply into the
various flow circuit tubes to insure that the refrigerant passing
through the capillaries is expanded well within each circuit.
This, in turn, precludes the refrigerant from being passed between
circuits by the dummy header. Because the dummy header is at a
substantially uniform pressure, the refrigerant is fed evenly into
each circuit.
The seventh capillary tube is passed into the liquid header 46
which is at relatively the same pressure as the dummy header.
Header 46, in turn, feeds into the circuit associated with heat
transfer zone G.
It should be noted that at this time check valve 51, positioned
between the primary and secondary headers 47 and 49 is now moved to
an open position so that the headers are cojoined to establish a
single flow passage leading to the compressor via line 50. As best
illustrated in Figure 5, the seven flow circuits are arranged to
empty into the headers 47, 49 when the coil is serving as an
evaporator. The circuits associated with zones G and F empty into
header 49 via lines 56 and 58 while the four circuits associated
with zone E empty into header 47 via lines 52.
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Accordingly, when the heat exchanger is called upon to serve as an
evaporator in the system, the flow geometry through the coil is
automatically changed whereby refrigerant is caused to flow through
all the circuits, and thus all the heat transfer zones,
simultaneously in a parallel flow arrangement. By maintaining this
parallel flow arrangement through the coil, optimum performance of
the exchanger can be obtained when utilized as an evaporator.
While this invention has been described with reference to the
structure herein disclosed, it is not confined to the specific
details as set forth. For example, in place of the capillary tubes
wherein employed any expansion device capable of carrying out the
flow splitting and throttling process can be similarly employed
provided such modifications come within the scope of the following
claims.
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