U.S. patent application number 13/265405 was filed with the patent office on 2012-02-16 for transcritical thermally activated cooling, heating and refrigerating system.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Joseph J. Sangiovanni, Igor B. Vaisman, Timothy C. Wagner, Craig R. Walker.
Application Number | 20120036854 13/265405 |
Document ID | / |
Family ID | 43032757 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120036854 |
Kind Code |
A1 |
Vaisman; Igor B. ; et
al. |
February 16, 2012 |
TRANSCRITICAL THERMALLY ACTIVATED COOLING, HEATING AND
REFRIGERATING SYSTEM
Abstract
A combined vapor compression and vapor expansion system uses a
common refrigerant which enables a super-critical high pressure
portion and a sub-critical low pressure portion of the vapor
expansion circuit. Provision is made to combine the refrigerant
flow from the vapor expander and from the compressor discharge. The
outdoor heat exchanger is so sized and designed that the working
fluid discharged therefrom is always in a liquid form so as to
provide a liquid into the pump inlet. The pump and expander are so
sized and designed that the high pressure portion of the vapor
expansion circuit is always super-critical. A topping heat
exchanger, liquid to suction heat exchanger, and various other
design features are provided to further increase the thermodynamic
efficiency of the system.
Inventors: |
Vaisman; Igor B.;
(Frederick, MD) ; Wagner; Timothy C.; (East
Hartford, CT) ; Sangiovanni; Joseph J.; (West
Suffield, CT) ; Walker; Craig R.; (South Glastonbury,
CT) |
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
43032757 |
Appl. No.: |
13/265405 |
Filed: |
April 28, 2010 |
PCT Filed: |
April 28, 2010 |
PCT NO: |
PCT/US2010/032726 |
371 Date: |
October 20, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61173776 |
Apr 29, 2009 |
|
|
|
Current U.S.
Class: |
60/671 ;
62/498 |
Current CPC
Class: |
F01K 17/02 20130101;
F01K 17/04 20130101; F25B 9/008 20130101; Y02A 30/274 20180101;
F25B 13/00 20130101; F25B 27/02 20130101; F25B 2309/061
20130101 |
Class at
Publication: |
60/671 ;
62/498 |
International
Class: |
F01K 25/08 20060101
F01K025/08; F25B 1/00 20060101 F25B001/00 |
Claims
1. A thermally activated cooling system comprising: a vapor
compression circuit which includes, in serial flow relationship, a
compressor, a first heat exchanger, an expansion device and a
second heat exchanger; a vapor expansion circuit which includes, in
serial flow relationship, a liquid refrigerant pump, a heater, an
expander, and said first heat exchanger; said vapor compression
circuit and said vapor expansion circuit each having a common
refrigerant circulating therethrough as a working fluid; wherein
said refrigerant enables supercritical high pressure portion and
sub-critical low pressure portion of the vapor compression circuit
said compressor having a suction inlet and a discharge outlet, and
said expander having an inlet and an outlet, and further wherein
said expander outlet is fluidly connected to said compressor outlet
to provide a combined flow for circulation of a portion of said
working fluid through said first heat exchanger and to said pump
wherein said first heat exchanger is so sized, and designed such
that the working fluid discharged therefrom is always in a liquid
form; and said pump and said expander are so sized and designed
that the high pressure portion of said vapor expansion circuit is
always super-critical.
2. A thermally activated cooling system as set forth in claim 1
where said common refrigerant is CO.sub.2.
3. A thermally activated cooling system as set forth in claim 1
where said common refrigerant is a mixture of CO.sub.2 and
propane.
4. A thermally activated cooling system as set forth in claim 1 and
including a topping heat exchange for causing heat to flow from the
expander discharge stream to the stream flowing to the heater.
5. A thermally activated cooling system as set forth in claim 1 and
including a liquid-to-suction heat exchanger for causing the flow
of heat from the condenser discharge stream to the evaporator
discharge stream.
6. A thermally activated cooling system as set forth in claim 1
wherein said expander is a two stage expander and further wherein a
second heater is provided between the two stages.
7. A thermally activated cooling system as set forth in claim 1 and
including a second vapor compression circuit in parallel with said
vapor compression circuit, said second vapor compression circuit
having its own expansion device, evaporator, and compressor fluidly
interconnected to function with said first heat exchanger.
8. A thermally activated cooling system as set forth in claim 1 and
including a plurality of valves for selectively causing the vapor
compression system to function as a heat pump.
9. A thermally activated cooling system as set forth in claim 8
wherein said plurality of valves includes two expansion devices,
one for the first heat exchanger and another for said second heat
exchanger.
10. A thermally activated cooling system as set forth in claim 8
wherein said plurality of valves includes a single bidirectional
expansion device which is selectively operated to conduct the flow
of refrigerant to either said first or second heat exchanger.
11. A thermally activated cooling system as set forth in claim 8
wherein said plurality of valves comprises a plurality of check
valves that are selectively operated to conduct the flow of
refrigerant to either the first or second heat exchanger.
12. A thermally activated cooling system as set forth in claim 1
and including a second heater connected in serial flow relationship
with said heater.
13. A thermally activated cooling system as set forth in claim 1
wherein said compressor comprises a multi-stage compressor, and
further including a gas cooler operably connected between said
stages.
14. A thermally activated cooling system as set forth in claim 1
wherein said compression circuit includes an ejector for boosting
the flow of refrigerant to said compressor.
15. A thermally activated cooling system as set forth in claim 14
wherein a refrigerant stream intended for cooling duty is split
into two portions; said ejector is powered by one portion of said
refrigerant stream and ejects another portion of said refrigerant
stream processed in said evaporator and then in said
liquid-to-suction heat exchanger.
16. A thermally activated cooling system as set forth in claim 14
wherein said compression circuit includes a suction accumulator; a
refrigerant stream intended for cooling duty powers said ejector
ejects liquid portion of said stream collected in said suction
accumulator and processed in said evaporator.
17. A thermally activated cooling system as set forth in claim 1
wherein said vapor compression circuit includes an economizer
operably connected therewith.
18. A thermally activated cooling system as set forth in claim 1
and including a two phase expander fluidly interconnected between
said condenser and said evaporator.
19. A thermally activated cooling system as set forth in claim 1
wherein said expander, said pump, and said compressor have a common
shaft
20. A thermally activated cooling system as set forth in claim 1
wherein a power generator and said expander have a common shaft and
said power generator powers said pump and said compressor.
21. A thermally activated cooling system as set forth in claim 1
wherein a power generator, said expander, and said pump have a
common shaft and said power generator powers said compressor.
22. A thermally activated cooling system as set forth in claim 1
wherein a power generator, said expander, and said compressor have
a common shaft and said power generator feeds said pump.
23. A thermally activated cooling system as set forth in claim 18
wherein said expander, said pump, and said compressor have a common
hermetic casing.
24. A power generation vapor expansion circuit which includes, a
power generator and, in serial flow relationship, a liquid
refrigerant pump, a heater, an expander, and a heat exchanger; a
refrigerant circulating therethrough as a working fluid wherein
said refrigerant enables supercritical high pressure portion and
sub-critical low pressure portion of the vapor expansion circuit;
said first heat exchanger is so sized, and designed such that the
working fluid discharged therefrom is always in a liquid form; and
said pump and said expander are so sized and designed that the high
pressure portion of said vapor expansion circuit is always
super-critical.
25. A power generation vapor expansion circuit as set forth in
claim 24 wherein said refrigerant is CO.sub.2.
26. A thermally activated cooling system as set forth in claim 24
where said common refrigerant is a mixture of CO.sub.2 and
propane.
27. A power generation vapor expansion circuit as set forth in
claim 24 and including a topping heat exchanger for causing heat to
flow from the expander discharge stream to the stream flowing to
the heater.
28. A power generation vapor expansion circuit as set forth in
claim 24 wherein said expander is a two stage expander and further
wherein a second heater is provided between the two stages.
29. A power generation vapor expansion circuit as set forth in
claim 24 and including a second heater connected in serial flow
relationship with said heater.
30. A power generation vapor expansion circuit as set forth in
claim 24 wherein said power generator, said expander, and said pump
have a common shaft.
31. A power generation vapor expansion circuit as set forth in
claim 24 wherein said power generator, said expander, and said pump
have a common hermetic casing.
32. A power generation vapor expansion circuit as set forth in
claim 24 wherein said power generator powers a refrigerating
system.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This disclosure relates to pending U.S. application Ser. No.
07/18958, assigned to the assignee of the present disclosure.
[0002] Reference is made to and this application claims priority
from and the benefit of U.S. Provisional Application Ser. No.
61/173,776, filed Apr. 29, 2009, entitled "TRANSCRITICAL THERMALLY
ACTIVATED COOLING, HEATING AND REFRIGERATING SYSTEM", which
application is incorporated herein in their entirety by
reference.
TECHNICAL FIELD
[0003] This disclosure relates generally to vapor compression
systems and, more particularly, to a combined vapor compression and
vapor expansion system.
BACKGROUND OF THE DISCLOSURE
[0004] It is known to combine a vapor compression system with a
vapor expansion, i.e. Rankine cycle, system. See, for example, U.S
Pat. No. 6,962,056, assigned to the assignee of the present
invention, and U.S Pat. No. 5,761,921.
[0005] U.S. Pat. No. 5,761,921 generates power in the Rankine cycle
which is then applied to drive the compressor of the vapor
compression cycle, and the combined systems operate on three
pressure levels, i.e. the boiler, condenser and evaporator pressure
levels. A common refrigerant R-134 is used in both the vapor
compression and the Rankine cycle systems. Such combined systems
have generally not allowed use of transcritical refrigerants, since
transcritical systems have generally not had a condenser (but only
a gas cooler), and therefore no liquid refrigerant available
downstream of the gas cooler for pumping through the Rankine
circuit. The expander requires a high entering pressure, but the
high inlet pressure elevates the boiling temperature and the
leaving temperature of the heating fluid carrying the thermal
power. The elevated leaving temperature reduces the extent of the
waste heat utilization. For those reasons the systems do not
sufficiently utilize available thermal energy and, therefore have a
low level of thermodynamic efficiency. Further, they do not provide
an adequate performance when the available hot source is below
180.degree. F.
[0006] U.S. patent application Ser. No. 07/18958 provides for a
combined flow of refrigerant from the two systems at the discharge
of the compressor and the expander, respectively. Further, a
suction accumulator is provided such that liquid refrigerant is
always available to the pump in the Rankine cycle system such that
transcritical operation is made possible. However, such use of a
suction accumulator may be undesirable because of the need for a
larger pump with greater power requirements. The pump power is
defined by a product of pressure differential across the pump and
the specific volume of the refrigerant stream at the pump inlet.
Although the liquid in the suction accumulator has a low specific
volume, the pump may be required to work against high pressure
differentials. When the disadvantage of the pressure differential
increase exceeds the advantage of the liquid specific volume
reduction, feeding of the pump with liquid refrigerant from the
condenser is considered to be an advantage over the use of a
suction accumulator.
DISCLOSURE
[0007] Briefly, in accordance with one aspect of the disclosure, a
combined vapor compression circuit and vapor expansion circuit
includes a common refrigerant which enables a supercritical high
pressure portion and a sub-critical low pressure portion of the
vapor expansion circuit, and combines the refrigerant from the
expander discharge and the compressor discharge at the entrance to
the outdoor heat exchanger. The outdoor heat exchanger is so sized
and designed that the refrigerant discharge therefrom is always in
a liquid form so that it can flow directly to the vapor expansion
circuit pump. The pump and expander are so sized and designed that
the high pressure portion of the vapor expansion circuit is always
super-critical.
[0008] In accordance with another aspect of the disclosure, the
outdoor heat exchanger includes a cooling tower to ensure that the
refrigerant is converted to a liquid in the heat exchanger.
[0009] In accordance with another aspect of the disclosure, a
liquid to suction heat exchanger is provided between the outdoor
heat exchanger and the pump in order to increase subcooling and
refrigerant density prior to the refrigerant liquid's passing to
the pump.
[0010] In accordance with yet another aspect of the invention, a
topping heat exchanger is provided downstream of the expander
outlet for the purpose of regenerating enthalpy of the hot
stream.
[0011] In accordance with yet another aspect of the invention, a
power generation vapor expansion circuit is used as a stand alone
system and generates electrical power, which may be used as an
electrical power supply for different purposes, including driving a
refrigeration system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a further understanding of these and objects of the
invention, reference will be made to the following detailed
description of the invention which is to be read in connection with
the accompanying drawing, where:
[0013] FIG. 1 is a schematic illustration of a thermally activated
refrigerant system for cooling or heating only.
[0014] FIG. 2 is a schematic illustration of a temperature-entropy,
(T-S) diagram of processes for the thermally activated refrigerant
system for cooling or heating only.
[0015] FIGS. 3A-3C are schematic illustrations comparing glides in
supercritical and subcritical applications, respectively.
[0016] FIG. 4 is a schematic illustration of a thermally activated
vapor expansion system with multi-stage expansion.
[0017] FIG. 5 is a schematic illustration of a T-S diagram of
processes for the thermally activated vapor expansion system with
multi-stage expansion.
[0018] FIG. 6 is a schematic illustration of a thermally activated
refrigerant system providing both air conditioning and
refrigeration.
[0019] FIG. 7 is a schematic illustration of a thermally activated
heat pump with two expansion devices.
[0020] FIG. 8 is a schematic illustration of a thermally activated
heat pump with one bidirectional expansion device.
[0021] FIG. 9A and 9B are schematic illustrations of reversing and
check valve arrangements, respectively.
[0022] FIG. 10 is a schematic illustration of a thermally activated
heat pump with two different hot sources.
[0023] FIG. 11 is a schematic illustration of a thermally activated
heat pump with multi-stage compression.
[0024] FIG. 12 is a schematic illustration of a thermally activated
heat pump with a vapor-to-vapor ejector.
[0025] FIG. 13 is a schematic illustration of a thermally activated
heat pump with a two-phase ejector.
[0026] FIG. 14 is a schematic illustration of a thermally activated
heat pump with an economized cycle.
[0027] FIG. 15 is a schematic illustration of a thermally activated
heat pump with a two-phase expander.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0028] While the present disclosure has been particularly shown and
described with reference to the preferred mode as illustrated in
the drawing, it will be understood by one skilled in the art that
various changes in detail may be effected therein without departing
from the spirit and scope of the disclosure as defined by the
claims.
[0029] In accordance with FIG. 1 a thermally activated refrigerant
system incorporates a vapor compression circuit 21 shown as solid
lines and a vapor expansion circuit 22 shown as dashed lines. The
vapor compression circuit 21 includes a compressor 23, a condenser
24, a liquid-to-suction heat exchanger 26, an expansion device 27,
and an evaporator 28. The vapor expansion circuit 22 consists of a
pump 29, a topping heat exchanger 31, a heater 32, an expander 33,
and the condenser 24. A refrigerant vapor stream at the outlet from
the compressor and a vapor refrigerant stream at the outlet from
the expander are connected at the condenser inlet to provide a
combined flow through the condenser 24. A refrigerant liquid stream
at the condenser outlet, or at the outlet of the liquid to suction
heat exchanger 26 as shown, splits into two streams: one feeds the
pump, and another circulates through the components of the vapor
compression circuit.
[0030] The thermally activated refrigeration system has three
pressure levels: a heating pressure, a heat rejection pressure
level, and evaporating pressure. The heating pressure is the pump
discharge pressure, the heat rejection pressure is compressor or
expander discharge, and the evaporating pressure is the compressor
suction pressure. The heating and heat rejection pressures are high
and low pressures of the vapor expansion circuit. The heat
rejection and evaporating pressures are high and low pressures of
the vapor compression circuit
[0031] One common working fluid is used for both the vapor
compression and the vapor expansion circuits. The working fluid has
the following feature: it provides super-critical operation for a
high pressure portion of the vapor expansion circuit and a
sub-critical operation for the low-pressure portion of the vapor
expansion circuit. Thus, the working fluid in the vapor expansion
circuit at the high pressure remains gaseous, but the working fluid
in the condenser appears in the region to the left of the vapor
dome and is liquefied. Examples of such working fluid are CO.sub.2
or CO.sub.2 based mixture, such as CO.sub.2 and propane, or the
like.
[0032] The heater 32 provides a thermal contact between a heating
medium and the pumped refrigerant stream. Usually the heat source
is a waste heat such as may be available from a fuel cell, a solar
device, a micro-turbine, a reciprocating engine, or the like.
Pressure in the heater is supercritical, that is, above the
critical pressure of the refrigerant. This provides a favorable
temperature glide compatible with a temperature glide of the
heating medium shown on FIG. 2. The heater 32 should be designed to
provide equality of heat capacity rates of both streams and enable
the highest temperature differentials across each stream. The
glides and equality of the heat capacity rates provide a higher
extent of waste heat utilization and a high entering expander
temperature, resulting in improved expander performance. If the hot
source is not a waste heat, the equality of heat capacity rates may
not be required; the temperature glide provides a higher
refrigerant temperature at the expander inlet, which improves the
performance characteristics of the expander.
[0033] The condenser 24 provides a thermal contact between a
cooling medium and the combined refrigerant stream outgoing from
the compressor 23 and expander 33. The temperature of the cooling
medium in the condenser 24 is always maintained below the
refrigerant critical point to enable refrigerant condensation at
the heat rejection pressure, with the liquid refrigerant feeding
the pump 29.
[0034] During periods of operation at higher ambient temperatures,
the condenser 24 may be fed by a cooling tower 34 to ensure
condensation of the refrigerant vapor. Another option is to use
CO.sub.2 and propane or the like in order to elevate the critical
point of the fluid sufficiently above the level of ambient
temperature to enable the condensation process at the heat
rejection pressure.
[0035] The heating pressure in the heater 32 is controlled by an
expander-to-pump capacity ratio, which is defined by an
expander-to-pump rotating speed ratio, a liquid refrigerant
temperature at the pump inlet, and a vapor refrigerant state at the
expander inlet.
[0036] The liquid-to-suction heat exchanger 26 is optional. It
slightly sub-cools a liquid stream outgoing from the condenser 24
and substantially superheats a vapor stream flowing from the
evaporator 28. The subcooling reduces the pump power due to
reduction of the refrigerant density at the pump inlet. Also, it
increases the enthalpy difference across the evaporator 28 and
increases the evaporator effect. The superheat decreases the
refrigerant density at the compressor inlet and reduces the
compressor mass flow rate and the evaporator capacity. The
superheat effect is usually stronger and the overall effect is
usually detrimental. Therefore, the liquid-to-suction heat
exchanger 26 is only used if a certain superheat at the compressor
inlet is required.
[0037] The topping heat exchanger 31 substantially improves
thermodynamic efficiency of the system when the hot source
temperature is high. When the hot source temperature is low, the
topping heat exchanger is not needed.
[0038] Power generated in the expander 33 may drive the compressor
23 and the pump 29. All three machines may be placed on the same
shaft. There is an option to couple the shaft with a power
generator 36 to provide not only cooling or heating duty, but also
electrical power. The expander 33 may be coupled with a power
generator only, in which case the power generator 36 powers the
compressor 23 and pump 29. In addition, optionally, it may generate
supplemental electrical power.
[0039] The vapor expansion circuit may be implemented as a separate
power generation system. Power generated in the power generation
system may be used to power a heat pump, air conditioner,
refrigerator, or any other electrical device.
[0040] All components sitting on the same shaft may be covered by a
semi-hermetic or hermetic casing to reduce risk of leakage.
[0041] The pump 29 may be a variable or multiple speed device or a
constant speed device. Speed variation helps to satisfy the
variable demands of refrigeration, air conditioning or heating.
[0042] Referring now to FIG. 2, the T-S diagram is shown for both
the vapor compression circuit 21 and the vapor expansion circuit 22
of FIG. 1, with the various points of interest in the two figures
being shown by the numerals 1-12. As will be seen, the line 9-10 is
representative of the temperature and enthalpy increases that occur
as the working fluid passes through the heater 32. Also, it should
be appreciated that the alternate dash-dot line 37 is indicative of
the T-S diagram for the cooled heating fluid passing through the
heater 32. In this regard, it is desirable to not only use hot
source fluids at temperatures of 180.degree. F. and above, as are
used in conventional systems, but also enable the use of hot source
fluids at temperatures below that level. This is made possible by
the "glide" or slope of the line 37 that results from the use of
CO.sub.2 as the working fluid. This will be more clearly understood
by reference to FIGS. 3A-3C.
[0043] Shown in FIG. 3A is a vapor expansion circuit which
includes, in serial flow relationship a pump 38, a topping heat
exchanger 39, a heater 41, an expander 42 and a condenser 43.
[0044] Shown in FIG. 3B is a T-S diagram for the FIG. 3A circuit
when operating in a supercritical mode such as with CO.sub.2 as the
refrigerant. The numbers 1-8 in FIG. 3B correspond to the positions
1-8 in the FIG. 3A drawing. As will be seen, the line 3-4 in FIG.
3B represents the increases in temperature and enthalpy as the
CO.sub.2 passes through the heater 41, and the alternate dash and
dot line 44 represents the T-S diagram for the cooled heating
fluid. It will recognized that the "glide", or the slope of this
line is substantial.
[0045] In contrast, the FIG. 3C illustration is a T-S diagram of
the FIG. 3A circuit when operating in a subcritical mode, i.e. with
a refrigerant other than CO.sub.2. Here, it will be recognized that
the glide/slope of the line 46 is substantially less than that of
the line 44 in FIG. 3B. The vertical component of the two lines 44
and 46, as shown by the arrowed lines 47 and 48, respectively, show
the degree of waste heat utilization of the two alternatives of
FIGS. 3B and 3C. As will be seen, the line 47 extends downwardly
further then the line 48 which, in turn, indicates that heat
sources (state 7) at lower temperatures may be employed as long as
the temperature in state 8 is below the temperature in state 7.
Thus, temperatures below 180.degree. F. may be suitable, such as,
for example, temperatures of 150.degree. F.
[0046] Referring now to FIG. 4, there is shown another embodiment
wherein, rather than a single stage expander 33 as shown in FIG. 1,
a two stage expander 49 is provided, as well as a second heater 51.
The second heater 51 receives the heating fluid along line 52 and
returns it to a point of the heater 32 by way of line 53. The
temperature of the heating fluid in the heater 51 should be equal
to the temperature of the point in the heater 32, where the line 53
is attached to. In operation, the refrigerant passes from the
heater 32 to the first stage of the two stage expander 49 and then
passes through the second heater 51, after which it passes through
the second stage of the two stage expander 49, and then to the
topping heat exchanger 31. The remainder of the circuit is as
described above. The effect of using the two stage expander 49 and
the second heater 51 is shown by the T-S diagram of FIG. 5 wherein
the numbers (1-14) are indicative of the locations indicated in
FIG. 4. It is known that the method of multi-stage expansion with
reheat improves the expander efficiency, and reduces required pump
power to thereby enable the use of smaller pumps and to reduce use
of pump power to thereby improve the overall efficiency of the
system.
[0047] Another embodiment is shown in FIG. 6 wherein a second vapor
compression circuit 54 is provided in parallel with the vapor
compression circuit 21. This enables the system to provide for both
air conditioning, i.e. by way of the second vapor compression
circuit 54 and refrigeration, i.e. by way of the vapor compression
circuit 21.
[0048] The second vapor compression circuit 54 includes a second
expansion device 56, a second evaporator or indoor unit 57 and a
second compressor 58. The flow of refrigerant for that circuit
originates upstream of the expansion device 27, and the discharge
flow from the second compressor 58 is combined with the refrigerant
flow from the topping heat exchanger 31 prior to the combination
being combined with the flow from the discharge of the compressor
23. Thus, each of the vapor compression circuits 21 and 54 has its
own compressor and evaporator unit, and all other components are
shared between the two circuits. As will be seen both of the
compressors are powered by the expander 33.
[0049] If the condenser 24 is an outdoor unit and the evaporator 28
is an indoor unit then the thermally activated refrigerant system
generates cooling. If the condenser is an indoor unit and the
evaporator is an outdoor unit then the thermally activated
refrigerant system generates heating. To switch between the two
modes of operation, one or more reversing or check valves may be
provided as shown in FIGS. 7-15.
[0050] In order to allow the system to operate as a heat pump, a
pair of reversing valves 59 and 61 are provided as shown in FIG. 7.
Further, in addition to the expansion device 27 that is operable
for use in the cooling mode, a second expansion device 62 is
provided for use in the heating mode. Each of the expansion devices
27 and 62 include a bypass valve, i.e. valves 63 and 64,
respectively, to permit operation in the respective cooling and
heating modes. The expansion devices 27 and 62 are single
directional expansion devices. In order to switch between the
cooling and heating modes, the reversing valves 59 and 61, and the
bypass valves 63 and 64, are all operated simultaneously.
[0051] A suction accumulator 66 maybe provided in order to satisfy
the refrigerant charge demands for cooling and heating operation.
Also, the suction accumulator 66 provides charge management and
capacity control accumulating redundant amount of liquid
refrigerant.
[0052] Further, a liquid-to-suction heat exchanger 67 may be
provided as indicated.
[0053] A variation of the FIG. 7 system is shown in FIG. 8 wherein
the two expansion devices are replaced by a single expansion device
68 which is designed for bi-directional use. Thus when switching
between the cooling and heating modes, the single expansion device
and the reversing valves 59 and 61 are all switched
simultaneously.
[0054] In FIG. 9A, the respective positions of the reversing valve
59 are shown to provide either cooling or heating operation. Thus,
in cooling, the refrigerant passes from the reversing valve 59
through the heat exchanger 67, the expansion device 27, and then to
the indoor unit. In heating, refrigerant passes from the reversing
valve 59, through the heat exchanger 67, the expansion 27, and then
to the outdoor unit.
[0055] As will be seen in FIG. 9B, rather than using reversing
valves as described hereinabove, check valves maybe substituted to
accomplish the same function. Thus, rather than reversing valves,
four check vales 71, 72, 73 and 74 are provided. In the cooling
mode, the refrigerant passes through the check valve 71, the heat
exchanger 67, the expansion device 27, and the check valve 73 to go
to the indoor unit, with check valves 72 and 74 being closed.
During operation in the heating mode, the check valves 71 and 73
are closed, and refrigerant passes through the check valve 74, the
heat exchanger 67, the expansion device 27, and the check valve 72
to pass then to the outdoor unit.
[0056] FIG. 10 represents a case when two hot sources, high
temperature and low temperature sources, are available. A second
heater 74 utilizes the high temperature source. The heater 32
utilizes the low temperature source.
[0057] A further embodiment is shown in FIG. 11 wherein a
multi-stage compressor 76 is provided. After passing through the
first stage, the refrigerant passes through a gas cooler 77, and
then through the second stage of the two stage compressor 76 before
passing to the reversing valve 61 and the condenser 24. In this
way, the total compressor power is reduced to thereby improve the
thermodynamic efficiency of the compression circuit and therefore
that of the total system.
[0058] The embodiment of FIG. 12 provides an ejector 78 for
boosting the flow of refrigerant vapor to the suction accumulator
66 to thereby improve the thermodynamic efficiencies of the vapor
compression circuit and of the total system. The ejector 78 is
driven by a high pressure stream along line 79 or, alternatively,
from lines 81 or 82. In this particular embodiment the
liquid-to-suction heat exchanger 67 is a mandatory component. The
heat exchanger 67 provides completion of evaporation of liquid
portion of the refrigerant stream outgoing from the ejector 78.
[0059] FIG. 13 embodiment shows a heat pump with an ejector 83
being driven by high pressure refrigerant from line 84 or,
alternatively, from line 86. The bi-directional expansion device 87
could be replaced by two one directional expansion devices, i.e.
one for the indoor unit and another for the outdoor unit as it was
shown above on FIG. 7.
[0060] It is known that ejectors improve performance
characteristics of vapor compression cycles. The combined vapor
compression and vapor expansion cycle improves with a better vapor
compression cycle.
[0061] Shown in FIG. 14 is an alternative embodiment that includes
an economizer cycle which includes an economizing heat exchanger
88, an economizer expansion device 89, and a economizer port 91
leading into a mid-stage of the compressor 23. A further
alternative may be that of a multi-stage compressor with
intermediate vapor cooling. It is known that economized cycles
improve performance characteristics of vapor compression cycles.
The combined vapor compression and vapor expansion cycles improves
with a better vapor compression cycle.
[0062] The FIG. 15 embodiment provides a two-phase expander 92
fluidly interconnected between an inlet to the pump 29 and the
reversing valve 59 as shown. Its use tends to increase the cooling
effect while recovering additional power to drive the cycle. This,
in turn, reduces required pump size and pump power.
[0063] Although the present disclosure has been particularly shown
and described with reference to a preferred embodiment as
illustrated by the drawings, it will be understood by one skilled
in the art that various changes in detail made be made thereto
without departing from the scope of the disclosure as defined by
the claims.
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