U.S. patent application number 12/091959 was filed with the patent office on 2008-09-25 for multi-circuit refrigerant system using distinct refrigerants.
Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20080229762 12/091959 |
Document ID | / |
Family ID | 38123189 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080229762 |
Kind Code |
A1 |
Lifson; Alexander ; et
al. |
September 25, 2008 |
Multi-Circuit Refrigerant System Using Distinct Refrigerants
Abstract
A multi-circuit refrigerant system includes a plurality of
circuits that are provided with distinct refrigerants. A control
selectively matches a sensed environmental space conditioning
challenge to selectively engage the plurality of circuits.
Inventors: |
Lifson; Alexander; (Manlius,
NY) ; Taras; Michael F.; (Fayetteville, NY) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
38123189 |
Appl. No.: |
12/091959 |
Filed: |
December 7, 2005 |
PCT Filed: |
December 7, 2005 |
PCT NO: |
PCT/US05/44147 |
371 Date: |
April 29, 2008 |
Current U.S.
Class: |
62/56 ;
62/467 |
Current CPC
Class: |
F25B 13/00 20130101;
F25B 49/02 20130101; F25B 2500/31 20130101; F25B 2500/29 20130101;
F25B 2700/2106 20130101; F25B 2400/06 20130101; F25B 1/00
20130101 |
Class at
Publication: |
62/56 ;
62/467 |
International
Class: |
F25D 3/12 20060101
F25D003/12 |
Claims
1. A refrigerant system comprising: a plurality of parallel
circuits, with each of said circuits including a compressor, an
outdoor heat exchanger, an expansion device, and an indoor heat
exchanger; and at least two distinct refrigerants used in a
plurality of said circuits.
2. The refrigerant system as set forth in claim 1, wherein there
are two distinct refrigerants
3. The refrigerant system as set forth in claim 1, wherein there
are two parallel circuits
4. The refrigerant system as set forth in claim 1, wherein each
circuit operation is controlled by a controller to achieve a
desired system operation.
5. The refrigerant system as set forth in claim 4, wherein said
controller selects an actuation order of said plurality of
circuits.
6. The refrigerant system as set forth in claim 4, wherein said
controller selects an amount of engagement time for each circuit
from a plurality of circuits.
7. The refrigerant system as set forth in claim 1, wherein said
distinct refrigerants include a first refrigerant that is best
suited for lower ambient conditions and a second refrigerant that
is best suited for higher ambient conditions, and a control sensing
an ambient temperature, and actuating said plurality of circuits
based upon said sensed ambient temperature, and an identification
of a circuit which is charged with the refrigerant best matched to
said sensed ambient temperature.
8. The refrigerant system as set forth in claim 7, wherein said
distinct refrigerants also include the first refrigerant best
suited for higher temperature range for an environment to be
conditioned and the second refrigerant that is best suited for
lower temperature range for an environment to be conditioned, and
the control using a demanded temperature range for actuating said
plurality of circuits based upon said sensed demanded temperature
range, and an identification of a circuit that is charged with the
refrigerant best matched to said demanded temperature range.
9. The refrigerant system as set forth in claim 7, wherein a
plurality of circuits may be actuated, with said identified circuit
actuated prior to the actuation of any other of said plurality of
circuits.
10. The refrigerant system as set forth in claim 1, wherein said
distinct refrigerants include the first refrigerant best suited for
higher temperature range for an environment to be conditioned and
the second refrigerant that is best suited for lower temperature
range for an environment to be conditioned, and the control using a
demanded temperature range for actuating said plurality of circuits
based upon said demanded temperature range, and an identification
of a circuit that is charged with the refrigerant best matched to
said demanded temperature range.
11. The refrigerant system as set forth in claim 10, wherein a
plurality of circuits may be actuated, with said identified circuit
actuated prior to the actuation of any other of said plurality of
circuits.
12. The refrigerant system as set forth in claim 1, wherein a
plurality of circuits may be actuated, with an identified circuit
actuated prior to the actuation of any other of said plurality of
circuits.
13. The refrigerant system as set forth in claim 1, wherein the
system is operating in a cooling mode.
14. The refrigerant system as set forth in claim 1, wherein the
system is operating in a heating mode.
15. The refrigerant system as set forth in claim 1, wherein said
refrigerant system is operable as a heat pump, and includes a flow
control device for selectively routing refrigerant from said
compressor to said outdoor heat exchanger initially in a cooling
mode, or initially to said indoor heat exchanger when in a heating
mode, and said plurality of refrigerants include a first
refrigerant that is best utilized in a refrigerant system in a
cooling mode, and a second refrigerant which is best utilized in a
refrigerant system in a heating mode, said control changes said
circuit actuation order dependent upon whether the refrigerant
system is in cooling mode or heating mode.
16. The refrigerant system as set forth in claim 1, wherein said
refrigerant system is operable as a heat pump, and includes a flow
control device for selectively routing refrigerant from said
compressor to said outdoor heat exchanger initially in a cooling
mode, or initially to said indoor heat exchanger when in a heating
mode, and said plurality of refrigerants includes a first
refrigerant that is best utilized in a refrigerant system in a
cooling mode, and a second refrigerant that is best utilized in a
refrigerant system in a heating mode, said control actuating both
circuits based on cooling and dehumidification demands.
17. The refrigerant system as set forth in claim 1, wherein the
first and second refrigerants are selected to provide distinct
capacities at different environmental conditions, and said control
sensing the environmental conditions, and utilizing the two
circuits in an order to achieve a desired capacity at the sensed
environmental conditions.
18. The refrigerant system as set forth in claim 1, wherein said
distinct refrigerants are selected from single component
refrigerants and multiple component refrigerant mixtures.
19. The refrigerant system as set forth in claim 1, wherein said
distinct refrigerants are mixtures consisting of the same
components, but with different compositions.
20. A method of operating a multi-circuit refrigerant system
comprising the steps of: (1) providing a plurality of refrigerant
circuits operating in parallel, a common control for said plurality
of refrigerant circuits and providing distinct refrigerants in a
plurality of said refrigerant circuits; and (2) selectively
operating said plurality of circuits for desired system
operation.
21. The method as set forth in claim 20, wherein said distinct
refrigerants include a first refrigerant that is best suited for
lower ambient conditions and a second refrigerant that is best
suited for higher ambient conditions, and a control sensing an
ambient temperature, and actuating said plurality of circuits based
upon said sensed ambient temperature, and an identification of a
circuit which includes the refrigerant best matched to said sensed
ambient temperature.
22. The method as set forth in claim 21, wherein said distinct
refrigerants also include the first refrigerant best suited for
higher temperature range for an environment to be conditioned and
the second refrigerant that is best suited for lower temperature
range for an environment to be conditioned, and the control using a
demanded temperature range for actuating said plurality of circuits
based upon said sensed demanded temperature range, and an
identification of a circuit that is charged with the refrigerant
best matched to said demanded temperature range.
23. The method as set forth in claim 22, wherein a plurality of
circuits may be actuated, with said identified circuit actuated
prior to the actuation of any other of said plurality of
circuits.
24. The method as set forth in claim 21, wherein a plurality of
circuits may be actuated, with said identified circuit actuated for
a majority of time as compared to any other of said plurality of
circuits.
25. The method as set forth in claim 20, wherein said distinct
refrigerants include the first refrigerant best suited for higher
temperature range for an environment to be conditioned and the
second refrigerant that is best suited for lower temperature range
for an environment to be conditioned, and the control using a
demanded temperature range for actuating said plurality of circuits
based upon said sensed demanded temperature range, and an
identification of a circuit that is charged with the refrigerant
best matched to said demanded temperature range.
26. The method as set forth in claim 25, wherein a plurality of
circuits may be actuated, with said identified circuit actuated
prior to the actuation of any other of said plurality of
circuits.
27. The method as set forth in claim 25, wherein a plurality of
circuits may be actuated, with said identified circuit actuated for
majority of the time as compared to any other of said plurality of
circuits.
28. The method as set forth in claim 20, wherein a plurality of
circuits may be actuated, with an identified circuit actuated prior
to the actuation of any other of said plurality of circuits.
29. The method as set forth in claim 20, wherein a plurality of
circuits may be actuated with an identified circuit actuated for
majority of the time as compared to any other of said plurality of
circuits.
30. The method as set forth in claim 20, wherein said refrigerant
system is operable as a heat pump, and includes a flow control
device for selectively routing refrigerant from said compressor to
said outdoor heat exchanger initially in a cooling mode, or
initially to said indoor heat exchanger when in a heating mode, and
said plurality of refrigerants includes a first refrigerant that is
best utilized in a refrigerant system in a cooling mode, and a
second refrigerant that is best utilized in a refrigerant system in
a heating mode, said control actuating both circuits based on
cooling and dehumidification demands.
31. The method as set forth in claim 20, wherein the first and
second refrigerants are selected to provide distinct capacities at
different environmental conditions, and said control sensing the
environmental conditions, and selectively operating said plurality
of circuits to achieve a desired capacity at the sensed
environmental conditions.
32. The method as set forth in claim 20, wherein the system is
operating in a cooling mode.
33. The method as set forth in claim 20, wherein the system is
operating in a heating mode.
34. The method as set forth in claim 20, wherein said refrigerant
system is operable as a heat pump, and includes a flow control
device for selectively routing refrigerant from said compressor to
said outdoor heat exchanger initially in a cooling mode, or
initially to said indoor heat exchanger when in a heating mode, and
said plurality of refrigerants include a first refrigerant that is
best utilized in a refrigerant system in a cooling mode, and a
second refrigerant which is best utilized when in a refrigerant
system in a heating mode.
Description
BACKGROUND OF THE INVENTION
[0001] This application relates to multi-circuit refrigerant
systems, wherein distinct refrigerants are used in the multiple
circuits to provide the ability to tailor operation to
environmental conditions and load requirements.
[0002] Refrigerant systems are utilized in many applications to
condition an environment. In particular, air conditioners and heat
pumps are employed to cool and/or heat air entering the
environment. The cooling or heating load of the environment may
vary with ambient conditions, occupancy level, other changes in
sensible and latent load demands, and as the temperature and/or
humidity set points are adjusted by an occupant of the
environment.
[0003] Multi-circuit refrigerant systems are also applied in the
industry, wherein several independent circuits operate under a
single control to provide various levels of sensible and latent
capacity in response to the external load demands and wherein each
circuit can independently function in one of several operational
regimes.
[0004] One option available to a designer of refrigerant systems
relates to the selection of available refrigerants. Various
refrigerants are known, and each has individual properties and
characteristics. Thus, the different refrigerants can provide
different capacities, efficiencies, dehumidification capabilities
as well as safety and toxicity levels, various degrees of
compatibility with the environment, etc.
[0005] For instance, some refrigerants, such as R134a, may be best
utilized in an air conditioning mode where the ambient temperatures
are relatively high, and other refrigerants, such as R410A, may be
better employed when ambient temperatures are typically lower.
Similarly, for heat pump applications, some refrigerants, such as
R744, might be best suited for the heating operations, while other
refrigerants, such as R245fa, may be better fitting for the cooling
operations.
[0006] In at least one proposed application, a composition of the
refrigerant circulating throughout the refrigerant system has been
selectively adjusted based upon the particular operation mode using
a rectification tower concept (see U.S. Pat. Nos. 6,070,420 and
5,848,537). However, the circuitry, system schematic, operation
control, etc. for altering and optimizing the refrigerant
composition is unduly complex and expensive.
SUMMARY OF THE INVENTION
[0007] In a disclosed embodiment of this invention, a refrigerant
system is provided with multiple circuits operating in parallel. At
least two of the circuits are provided with distinct refrigerants.
In one example, the refrigerant system is an air conditioning
system, and the two refrigerants may be selected to be best
utilized at distinct ambient temperatures. As an example, each
refrigerant might provide efficiency benefits at the indicated
temperature range. One circuit may be charged with a refrigerant
best utilized at higher ambient temperatures, while the other
circuit may have a refrigerant best utilized at lower ambient
temperatures. The control for the system monitors the ambient
temperature, and utilizes the two circuits in a sequence based upon
a sensed ambient temperature.
[0008] As is known, controls for multiple circuits operate the
circuits in combination with each other to best address a
particular environmental conditioning situation. The control in
this invention is operable to sense ambient temperature, and
initially use the circuit charged with the refrigerant that is best
suited for an existing ambient temperature range. Generally, the
other circuit is engaged only if an additional boost in capacity is
required. Thus, the circuit that is most efficient for the
particular environmental situation provides the bulk of the space
conditioning. The other circuit is utilized less frequently and as
a "trimming" circuit. That is, it is utilized to supplement the
main circuit. In case the environmental conditions change
significantly enough for the refrigerant circulating through
another independent circuit of a multi-circuit refrigerant system
to be more efficient, then that circuit becomes primary and is
brought online first to address space conditioning demands.
[0009] In another embodiment, similar strategy can be exercised in
relation to the temperature ranges for the environment to be
conditioned. For example, one refrigerant can be mostly
thermodynamically advantageous for a higher temperature range and
the other refrigerant may have benefits at the lower temperature
range. The system control determines and optimizes a sequence of
operation for the multi-circuit refrigerant system in accordance to
the sensed conditioned space temperature. In a logical extension of
this control strategy, both indoor and outdoor temperatures could
be utilized for determination of an appropriate (for instance, most
efficient) sequence of operation based on a two-dimensional map
with indoor and outdoor temperatures as independent variables.
[0010] In still another embodiment, the refrigerant system is a
heat pump having multiple circuits. One of the multiple heat pump
circuits is provided with a refrigerant that is most efficient for
cooling situations, and another circuit is provided with the
refrigerant which is most efficient for heating situations. Again,
the control is operable to initially utilize the circuit which is
charged with the best refrigerant as a "main" circuit for the
particular operation. Further, when it is desired to simultaneously
operate some independent circuits of a multi-circuit system in the
air conditioning mode and some circuits in the heat pump mode, for
instance, to control humidity, the best refrigerant is matched to a
particular mode of operation by the system controls.
[0011] In yet another embodiment, since the circuits charged with
different refrigerants are inherently unbalanced (or provide
different capacities at identical environmental conditions), the
system controls utilize an operational sequence logic to optimize
overall unit performance and reliability based on minimizing a
number of start-stop cycles (and associated losses) to match
particular capacity demands as well as taking into account
continuous operational efficiency of a particular circuit charged
with a particular refrigerant.
[0012] Furthermore, the some circuits could be provided with a
single component refrigerant ("pure substance" refrigerant) while
the other circuits could be provided with a mixture of multiple
constituent refrigerants or the circuits can each be provided with
a refrigerant mixture consisting of different components. In one
embodiment, this mixture can consist of the same distinct
refrigerant constituents mixed in different compositions
(proportions) between the two circuits.
[0013] While the embodiments disclosed include only two circuits,
it should be understood that additional circuits could be utilized
within this invention. A worker of ordinary skill in the art would
recognize which refrigerants are best suited for the particular
challenges.
[0014] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows a first schematic.
[0016] FIG. 2 shows a second schematic.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] FIG. 1 shows a refrigerant system that may be utilized as an
air conditioning system, and which includes a plurality of circuits
50 arranged in a parallel fashion. Each circuit 50 includes a
compressor 12 delivering refrigerant to a condenser 20, to an
expansion device 22, and to an evaporator 24. For cooling
applications, the condenser 20 in an air conditioning system is
positioned outside of the environment to be conditioned while the
evaporator 24 is positioned as an inside heat exchanger.
[0018] The two circuits 50 are provided with distinct refrigerants.
In one embodiment, a control 100 is operable to sense ambient
temperature. One circuit 50 is charged with a refrigerant that is
best utilized at higher ambient temperatures, and the other circuit
is provided with a refrigerant that is best utilized at lower
ambient temperatures. The control 100 controls both circuits 50.
Based upon a sensed ambient temperature, the control 100 selects
which circuit 50 to be utilized initially to meet cooling demands.
As an example, should the ambient temperature be somewhat low, the
circuit 50, that is charged with the refrigerant that is best
utilized at lower ambient temperatures, is initially brought online
to meet a cooling load. If additional cooling is necessary to
satisfy the cooling requirements, then the other circuit, which is
"less-suited" for lower ambient temperatures, is actuated and used
as a trimming circuit to fully meet the cooling demand.
[0019] Conversely, should a higher ambient temperature be sensed by
the control 100, then the circuits are used in a reverse order.
[0020] The present invention thus provides the ability to utilize
distinct refrigerants to most efficiently and accurately meet a
cooling challenge. It has to be noted that refrigerant systems
typically operate at part-load conditions most of the time, so a
supplementary circuit with "less-suited" refrigerant will be
utilized very seldom and the attained benefits of matching
refrigerant to particular environmental conditions will not be
compromised.
[0021] Further, similar strategy can be exercised in relation to
the temperature ranges for the environment to be conditioned. One
refrigerant can be mostly thermodynamically advantageous for a
higher temperature range and the other refrigerant may have
benefits at the lower temperature range. The control 100 will
determine and optimize a sequence of operation for the
multi-circuit refrigerant system in accordance to the sensed
conditioned space temperature. Also, as a logical extension of this
control strategy, both indoor and outdoor temperatures could be
utilized for determination of an appropriate (for instance, most
efficient) sequence of operation based on a two-dimensional map
with indoor and outdoor temperatures as independent variables.
Obviously, this invention extends to the refrigerants operating in
trans-critical and super-critical regions as well.
[0022] In the heating applications, the condensers 20 would be
located indoors and the evaporators 24 positioned outdoors, but the
abovementioned logic for the control 100 with respect to indoor and
outdoor temperatures would be preserved (although may be referenced
to a different performance map).
[0023] Also, more than two circuits and more than two refrigerants
can be utilized within multi-circuit system configurations.
[0024] FIG. 2 shows another embodiment wherein heat pumps are
utilized in a multi-circuit system. As shown, there is a pair of
circuits 10. Of course, a different number of circuits and more
than two distinct refrigerants would be within the scope of this
invention. Each circuit 10 includes a compressor 12 delivering
refrigerant to a discharge line 14. A suction line 16 returns
refrigerant to the compressor 12. A four-way valve 18 selectively
routes refrigerant from the discharge line 14 to either an outdoor
heat exchanger 20 in the cooling (or air conditioning) mode of
operation, or to an indoor heat exchanger 24 in the heating (or
heat pump) mode of operation. In the cooling mode, the four-way
valve 18 routes the refrigerant to the outdoor heat exchanger 20,
then to an expansion device 22, and then to the indoor heat
exchanger 24, from where it is returned, through the four-way valve
18 and suction line 16, to the compressor 12. In the heating mode,
a direction of the refrigerant flow through the system is
essentially reversed, and the refrigerant flows from the compressor
12, through the four-way valve 18, through the indoor heat
exchanger 24, through the expansion device 22, through the outdoor
heat exchanger 20, and then again through the four-way valve 18 and
through the suction line 16 back to the compressor 12. This general
operation is as known in the art. The four-way valve 18 is
controlled to either achieve cooling or heating mode of operation.
Furthermore, if the expansion device cannot handle the reversing
flow, then, as one of the potential solutions, a pair of
unidirectional expansion devices, with corresponding check valves,
may be employed instead.
[0025] One of the multiple heat pump circuits 10 is provided with a
refrigerant that is most efficient for cooling situations, and the
other circuit is provided with a refrigerant, which is most
efficient for heating situations. Again, the control 100 is
operable to initially utilize the circuit which includes the best
refrigerant for the particular operation. Further, a similar
strategy could be employed for providing humidity comfort as well,
while simultaneously operating one of the heat pump circuits in the
cooling mode and the other circuit in the heating mode and while
the best refrigerant is matched to a particular mode of operation
by the control 100.
[0026] Also, since the circuits containing different refrigerants
will be inherently unbalanced (typically delivering different
capacity levels at identical environmental conditions), an
operating sequence can be developed to optimize the unit
performance by reducing the cycling losses while selecting the
circuit to minimize, for example, an overall number of starts and
stops. Further, an optimization strategy can be developed where
efficiency of operation of each circuit at particular conditions
and the cycling losses are evaluated at the same time to determine
the most efficient and reliable sequence/control logic of unit
operation. In all cases considered above, a transducer
communication feedback of system operating and/or environmental
conditions to the control 100 will be a deciding factor of
switching between the circuits on a primary-secondary basis.
[0027] A main aspect of the invention is that each circuit in the
multi-circuit refrigerant system may have a different refrigerant,
which provides enhanced capability in system operation and control
in satisfying a wide spectrum of external sensible and latent load
demands. The teachings of this invention are not limited to a
specific system configuration or refrigerant, and the benefits of
the invention can be easily extended to other design arrangements
by a person ordinarily skilled in the art. Also, it has to be
noted, that a refrigerant can be a mixture of various components
("pure" substances), and changing a composition of such a mixture
would constitute a different refrigerant as well.
[0028] Providing an appropriate control for operation of all of the
refrigerant system components and devices would also be within the
skill of a worker in this art.
[0029] Although a preferred embodiment of this invention has been
disclosed, a worker of ordinary skill in this art would recognize
that certain modifications would come within the scope of this
invention. For that reason, the following claims should be studied
to determine the true scope and content of this invention.
* * * * *