U.S. patent application number 10/950959 was filed with the patent office on 2005-06-16 for refrigeration system with reverse flow defrost.
Invention is credited to Marchand, Jeffrey Jules, McAlpine, Douglas M., Tamburrino, Daniel.
Application Number | 20050126198 10/950959 |
Document ID | / |
Family ID | 34676885 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050126198 |
Kind Code |
A1 |
Marchand, Jeffrey Jules ; et
al. |
June 16, 2005 |
Refrigeration system with reverse flow defrost
Abstract
A refrigeration system including a compressor operable to
discharge compressed refrigerant. A first heat exchanger is
operable to cool the compressed refrigerant. The first heat
exchanger includes a first inlet, an outlet, and a second inlet
disposed between the first inlet and the outlet. A second heat
exchanger is disposed adjacent a cool space. A valve is movable
between a first position to direct the compressed refrigerant to
the first inlet and then to the second heat exchanger to cool the
second heat exchanger and a second position to direct the
compressed refrigerant to the second heat exchanger and then to the
second inlet to heat the second heat exchanger.
Inventors: |
Marchand, Jeffrey Jules;
(Ontario, CA) ; Tamburrino, Daniel; (Dacula,
GA) ; McAlpine, Douglas M.; (Bartlett, IL) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Family ID: |
34676885 |
Appl. No.: |
10/950959 |
Filed: |
September 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60529301 |
Dec 12, 2003 |
|
|
|
Current U.S.
Class: |
62/278 |
Current CPC
Class: |
F25B 41/22 20210101;
F25B 47/022 20130101; F25B 2400/075 20130101; F25B 2400/16
20130101; F25B 2347/021 20130101; F25B 5/02 20130101; F25B 1/047
20130101 |
Class at
Publication: |
062/278 |
International
Class: |
F25B 047/00 |
Claims
What is claimed is:
1. A refrigeration system comprising: a compressor operable to
discharge compressed refrigerant; a first heat exchanger operable
to cool the compressed refrigerant, the first heat exchanger
including a first inlet, an outlet, and a second inlet disposed
between the first inlet and the outlet; a second heat exchanger
disposed adjacent a cool space; and a valve movable between a first
position to direct the compressed refrigerant to the first inlet
and then to the second heat exchanger to cool the second heat
exchanger and a second position to direct the compressed
refrigerant to the second heat exchanger and then to the second
inlet to heat the second heat exchanger.
2. The refrigeration system as set forth in claim 1 wherein the
compressor comprises an oil-flooded screw compressor.
3. The refrigeration system as set forth in claim 1 wherein the
compressor comprises a plurality of compressors, each compressor
operable to discharge compressed refrigerant to a common
header.
4. The refrigeration system as set forth in claim 1 wherein the
second heat exchanger comprises a plurality of evaporators.
5. The refrigeration system as set forth in claim 4 wherein each of
the plurality of evaporators is in selective fluid communication
with a liquid header and a suction header.
6. The refrigeration system as set forth in claim 4 further
comprising a plurality of defrost valves, each defrost valve
positioned to provide selective fluid communication between a hot
gas header and one of the plurality of evaporators.
7. The refrigeration system as set forth in claim 6 wherein each of
the plurality of defrost valves comprises a solenoid-actuated
valve.
8. A refrigeration system comprising: a plurality of compressors,
each compressor operable to discharge compressed refrigerant; a
first heat exchanger operable to cool the compressed refrigerant,
the first heat exchanger comprising a first inlet, an outlet, and a
second inlet between the first inlet and the outlet; a plurality of
evaporators; a receiver in fluid communication with the first heat
exchanger and in selective fluid communication with each of the
plurality of evaporators; a hot gas header; a valve movable between
a first position to direct the compressed refrigerant to the first
inlet and a second position to direct the compressed refrigerant to
the hot gas header; and a plurality of defrost valves, each defrost
valve movable between a first position to place the receiver in
fluid communication with one of the plurality of evaporators to
cool the evaporator and a second position to place the hot gas
header in fluid communication with the one of the plurality of
evaporators to heat the evaporator, the evaporator discharging
refrigerant to the second inlet when the defrost valve is in the
second position.
9. The refrigeration system as set forth in claim 8 wherein each of
the compressors comprises an oil-flooded screw compressor.
10. The refrigeration system as set forth in claim 8 wherein each
of the plurality of evaporators is in selective fluid communication
with a liquid header and a suction header.
11. The refrigeration system as set forth in claim 8 wherein at
least one of the plurality of defrost valves is positioned in the
first position when another of the plurality of defrost valves is
in the second position.
12. The refrigeration system as set forth in claim 8 wherein each
of the plurality of defrost valves comprises a solenoid-actuated
valve.
13. A method of operating a refrigeration system comprising:
operating a compressor to deliver compressed refrigerant; directing
the compressed refrigerant to a first inlet of a first heat
exchanger; condensing the compressed refrigerant within the first
heat exchanger; expanding a portion of the compressed refrigerant;
passing the portion of the expanded compressed refrigerant through
a second heat exchanger to cool the heat exchanger; manipulating a
valve to redirect the compressed refrigerant to the second heat
exchanger to heat the second heat exchanger; and directing the
compressed refrigerant to a second inlet of the first heat
exchanger, the second inlet disposed downstream of the first
inlet.
14. The method as set forth in claim 13 wherein operating the
compressor comprises operating at least one of a plurality of
compressors to deliver compressed refrigerant to a common
header.
15. The method as set forth in claim 13 wherein the second heat
exchanger comprises a plurality of evaporators.
16. The method as set forth in claim 15 wherein at least one of the
plurality of evaporators is cooled and at least one of the
plurality of evaporators is heated simultaneously.
17. The method as set forth in claim 15 further comprising
separating the portion of compressed refrigerant into a plurality
of flow streams and expanding each stream.
18. The method as set forth in claim 15 wherein the manipulating
step redirects at least a portion of the compressed refrigerant to
a hot gas header.
19. The method as set forth in claim 18 further comprising
actuating at least one of a plurality of defrost valves to direct
compressed refrigerant from the hot gas header to at least one of
the evaporators.
20. The method as set forth in claim 13 further comprising
directing the compressed refrigerant to the first heat exchanger
after passing the compressed refrigerant through the second heat
exchanger.
Description
RELATED APPLICATION DATA
[0001] This application claims benefit under 35 U.S.C. Section
119(e) of U.S. Provisional Application No. 60/529,301 filed Dec.
12, 2003.
BACKGROUND
[0002] The present invention relates generally to a refrigeration
system. More particularly, the present invention relates to a
refrigeration system that includes a defrost cycle.
[0003] Refrigeration systems cool a space by supplying cold
refrigerant to an evaporator. Water vapor in the space being cooled
sometimes condenses onto the outer surface of the evaporator and
forms layers of ice. These layers of ice reduce the efficiency of
the evaporator and make it difficult to maintain the desired
temperature within the space.
SUMMARY
[0004] In one embodiment, the invention provides a refrigeration
system including a compressor operable to discharge compressed
refrigerant. A first heat exchanger is operable to cool the
compressed refrigerant. The first heat exchanger includes a first
inlet, an outlet, and a second inlet disposed between the first
inlet and the outlet. A second heat exchanger is disposed adjacent
a cool space. A valve is movable between a first position to direct
the compressed refrigerant to the first inlet and then to the
second heat exchanger to cool the second heat exchanger and a
second position to direct the compressed refrigerant to the second
heat exchanger and then to the second inlet to heat the second heat
exchanger.
[0005] In another embodiment, the invention provides a
refrigeration system including a plurality of compressors. Each
compressor is operable to discharge compressed refrigerant. A first
heat exchanger is operable to cool the compressed refrigerant. The
first heat exchanger includes a first inlet, an outlet, and a
second inlet between the first inlet and the outlet. The system
also includes a plurality of evaporators and a receiver in fluid
communication with the first heat exchanger and in selective fluid
communication with each of the plurality of evaporators. The system
further includes a hot gas header and a valve that is movable
between a first position to direct the compressed refrigerant to
the first inlet and a second position to direct the compressed
refrigerant to the hot gas header. A plurality of defrost valves
are movable between a first position to place the receiver in fluid
communication with one of the plurality of evaporators to cool the
evaporator and a second position to place the hot gas header in
fluid communication with the one of the plurality of evaporators to
heat the evaporator. The evaporator discharges refrigerant to the
second inlet when the defrost valve is in the second position.
[0006] In yet another embodiment, the invention provides a method
of operating a refrigeration system including operating a
compressor to deliver compressed refrigerant. The method also
includes directing the compressed refrigerant to a first inlet of a
first heat exchanger and condensing the compressed refrigerant
within the first heat exchanger. The method further includes
expanding a portion of the compressed refrigerant and passing the
portion of the expanded compressed refrigerant through a second
heat exchanger to cool the heat exchanger. The method also includes
manipulating a valve to redirect the compressed refrigerant to the
second heat exchanger to heat the second heat exchanger and
directing the compressed refrigerant to a second inlet of the first
heat exchanger. The second inlet is disposed downstream of the
first inlet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The detailed description particularly refers to the
accompanying figures in which:
[0008] FIG. 1 is a circuit diagram for a refrigeration system
illustrating the flow paths in a refrigeration mode; and
[0009] FIG. 2 is a circuit diagram for a refrigeration system
illustrating the flow paths in a defrost mode.
DETAILED DESCRIPTION
[0010] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following figures. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. Unless specified or limited otherwise,
the terms "mounted," "connected," "supported," and "coupled" and
variations thereof are used broadly and encompass both direct and
indirect mountings, connections, supports, and couplings. Further,
"connected" and "coupled" are not restricted to physical or
mechanical connections or couplings.
[0011] The basic configuration of a refrigeration system 10
generally includes the conventional components of a
vapor-compression or refrigeration cycle (i.e., compressor(s) 15,
condenser(s) 20, evaporator(s) 25, a receiver(s) 30, and expansion
valve(s) 35). As one of ordinary skill will realize, refrigeration
systems may incorporate multiple compressors 15, evaporators 25,
and/or condensers 20 in parallel or in series to accomplish the
goals of the particular system. As such, the invention should not
be limited to systems that include components arranged or numbered
as illustrated herein. It should be understood that the invention
hereinafter described is not dependent upon the number or size of
such components.
[0012] Before describing the figures in detail, it should also be
noted that the figures have been simplified for the purpose of
illustration. Components such as check valves, drain and fill
valves, pressure taps, flow meters, sensors, parallel piping, as
well as other types of components have been omitted for
clarity.
[0013] FIGS. 1 and 2 show the basic layout of one arrangement of a
refrigeration system 10 incorporating a reverse flow defrost. FIG.
1 shows the flow through a portion of the system when operating in
a refrigeration mode and FIG. 2 illustrates the same portion of the
system operating in a defrost mode.
[0014] With reference to FIG. 1, the flow in refrigeration mode
begins when one or more compressors 15 draw superheated refrigerant
vapor (e.g., R12, ammonia, CFCs, HCFCs, HFCs, etc.) from a suction
header 40. The term "superheated" as used herein includes any
refrigerant that contains vapor at or above the saturation
temperature for the refrigerant at the particular pressure. The
compressor 15 compresses the vapor to produce a flow of
superheated, high-pressure refrigerant. The vapor passes through a
defrost differential valve 45 that is maintained in an open
position when operating in refrigeration mode. From the defrost
differential valve 45, the flow passes through the condenser 20,
entering through a condenser inlet 50 and exiting through a
condenser outlet 55. In the condenser 20, the flow cools and
condenses to produce a high-pressure flow of cool liquid
refrigerant that is directed into the receiver 30. From the
receiver 30, liquid refrigerant is directed to a liquid header 60
that is positioned to supply refrigerant to one, or more than one,
of a plurality of cooling paths 65. It should be noted that the
term "header" should be read broadly to include structures as
simple as a pipe or manifold that are able to deliver or receive a
fluid to/from a plurality of flow paths.
[0015] For the sake of simplicity, only one complete cooling path
65 is illustrated in FIGS. 1 and 2. The remaining cooling paths 65
are similar to the illustrated path 65. Each cooling path 65
includes an expansion valve 35 and the evaporator 25. The expansion
valve 35 expands the flow of vapor to reduce the temperature and
pressure of the flow prior to its entry into the evaporator 25.
After the flow passes through the evaporator 25, it is returned to
the suction header 40 and the cycle repeats.
[0016] Each evaporator 25 is positioned to cool a space.
Alternatively, multiple evaporators may be used to cool a single
space if necessary. The cold refrigerant passes through the
evaporator 25 and is heated by the environment in which the
evaporator 25 is positioned. Typically, air or another fluid moves
across the evaporator 25 and is cooled by the refrigerant as the
refrigerant is heated. In some constructions, fans (not shown) are
used to move the air across the evaporator 25. The refrigerant is
usually heated such that it leaves the evaporator 25 as superheated
refrigerant, while the air is cooled and returned to the cool
space. Depending on the environment in which the evaporator 25 is
positioned, the cold temperature of the evaporator 25 may cause
some of the water vapor in the air to condense and freeze onto the
evaporator 25. The freezing water forms layers of ice that reduce
the efficiency of the heat exchange between the environment being
cooled and the refrigerant within the evaporator 25. To improve the
evaporator efficiency, the layers of ice generally need to be
removed.
[0017] To remove the ice, the refrigeration system 10 periodically
transitions into a defrost mode. The flows within the refrigeration
system 10 when in the defrost mode are illustrated in FIG. 2. A
portion of the hot compressed gas exiting the compressors is
directed to a hot gas header 70. The defrost differential valve 45
at least partially controls the quantity of hot compressed gas that
is directed to the hot gas header 70. For example, when additional
hot gas is required in the hot gas header 70, the defrost
differential valve is closed slightly or closed completely to
reduce the size of the flow path to the condenser 20. The reduced
flow path effectively redirects an increased quantity of hot gas to
the hot gas header 70. As one of ordinary skill will realize, other
constructions could position the defrost differential valve 45
differently. For example, one construction places the defrost
differential valve 45 in the flow path to the hot gas header 70. In
this position, opening the valve increases the flow to the hot gas
header 70.
[0018] The hot gas header 70 is selectively connected with each of
the cooling paths 65. A defrost valve 72 is positioned within each
cooling path 65 to inhibit the flow of refrigerant to the hot gas
header 70 when in the cooling mode. In the illustrated
construction, a solenoid-operated valve is used as the defrost
valve 72 in each cooling path 65. However, other constructions may
use other types of valves or other actuation means (e.g., manual)
for the defrost valves 72. To transition one of the cooling paths
65 from the refrigeration mode to the defrost mode, the system may
close the defrost differential valve 45 to direct additional hot
compressed refrigerant to the hot gas header 70 if necessary. The
defrost valve 72 corresponding to the cooling path 65 to be heated
is opened to direct a flow of hot compressed refrigerant to the
evaporator. In addition, an isolation valve 74 is closed to inhibit
flow of hot gas from the hot gas header 70 directly to the suction
header 40.
[0019] As with the refrigeration mode, the defrost cycle begins
when the compressor 15 draws superheated refrigerant vapor from the
suction header 40. However, with the defrost differential valve 45
reducing or completely preventing flow to the condenser 20, part or
all of the flow is redirected to the hot gas header 70. The hot gas
header 70 directs the flow of superheated, high-pressure
refrigerant vapor through the evaporator 25 in the opposite
direction it would flow if in the refrigeration mode. The
superheated high-pressure vapor heats the evaporator 25 and melts
the accumulated ice. After passing through the evaporator 25, the
refrigerant collects in a hot gas return header 75.
[0020] The hot gas return header 75 directs the refrigerant to the
condenser 20. The flow enters the condenser 20 at a defrost inlet
80 located downstream of the condenser inlet 50. After passing
through the condenser 20, the now cooled liquid flows into the
receiver tank 30. In an alternative construction, a separate heat
exchanger (not shown), having the ability to remove heat (heat
removed via air/water or other means) and condense the refrigerant
from a vapor to a liquid, receives the flow of refrigerant vapor
from the hot gas return header 75 and directs the condensed
refrigerant to a reentry point at or after the condenser outlet
55.
[0021] As one of ordinary skill will realize, operation in defrost
mode directs vapor from the suction header 40 to the hot gas header
70, through the evaporator 25 being defrosted, through the
condenser 20, and finally to the receiver tank 30. However, if none
of the evaporators 25 in the system are operating in refrigeration
mode, none of the refrigerant will be drawn from the receiver tank
30. As such, no refrigerant will flow to the suction header 40, and
eventually no refrigerant will be available to the compressors 15.
As such, at least one cooling path 65 is generally maintained in
the refrigeration mode during a defrost cycle to assure that
refrigerant is always available to the compressors 15. With at
least one evaporator 25 operating in refrigeration mode,
refrigerant is drawn from the receiver tank 30 and returned to the
suction header 40, thus completing the defrost cycle.
[0022] For the sake of clarity, only one evaporator 25 is
illustrated herein. However, it should be understood that multiple
evaporators 25 are typically employed in systems of this type. In
fact, to operate in the defrost mode for a long duration, one
evaporator 25 should be operated in the refrigeration mode as just
described to prevent the depletion of the refrigerant. Typically,
several evaporators 25 within the system operate in refrigeration
mode with the remaining evaporators 25 operating in defrost mode.
Of course, all of the evaporators 25 can be operated in
refrigeration mode at the same time if desired.
[0023] Although the invention has been described in detail with
reference to certain preferred embodiments, variations and
modifications exist within the scope and spirit of the invention.
Thus, the invention provides, among other things, a new and useful
system and method of cooling multiple spaces and defrosting the
individual evaporators. The constructions of the system and the
methods of operation of the system described above and illustrated
in the figures are presented by way of example only and are not
intended as a limitation upon the concepts and principles of the
invention. Various features and advantages of the invention are set
forth in the following claims.
* * * * *