U.S. patent application number 12/738300 was filed with the patent office on 2010-08-19 for integrated refrigerating/freezing system and defrost method.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Chuanxue Duan, Zhong Gu, Zhiwei He.
Application Number | 20100205984 12/738300 |
Document ID | / |
Family ID | 40568078 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100205984 |
Kind Code |
A1 |
Gu; Zhong ; et al. |
August 19, 2010 |
Integrated Refrigerating/Freezing System and Defrost Method
Abstract
A medium and low-temperature integrated refrigeration/freezing
system (100) has the function of discharge gas defrosting. It
comprises medium and low-temperature compressors sets (120, 122)
and medium and low-temperature evaporators, as well as control
valves (141, 142, 143, 144), adjusting valves (145, 146), one-way
valves (147, 148) and expansion valves (150, 152, 154), and the
switching between a refrigerating cycle and the discharge gas
defrosting cycle is performed by the combination of actions between
multiple control valves. When a first control valve is opened, a
second valve is closed and a fourth valve is closed to the
refrigerant pipeline to said reservoir, the refrigerating cycle
operation is performed; and when the first control valve is closed,
the second valve is opened and the fourth valve is closed to the
refrigerant pipeline of an intercooler (128), the discharge gas
defrosting operation is performed.
Inventors: |
Gu; Zhong; (Shanghai,
CN) ; He; Zhiwei; (Shanghai, CN) ; Duan;
Chuanxue; (Shanghai, CN) |
Correspondence
Address: |
BACHMAN & LAPOINTE, P.C. (UTC)
900 CHAPEL STREET, SUITE 1201
NEW HAVEN
CT
06510-2802
US
|
Assignee: |
CARRIER CORPORATION
Farmington
US
|
Family ID: |
40568078 |
Appl. No.: |
12/738300 |
Filed: |
October 17, 2008 |
PCT Filed: |
October 17, 2008 |
PCT NO: |
PCT/US08/80298 |
371 Date: |
April 27, 2010 |
Current U.S.
Class: |
62/81 ; 165/62;
62/156; 62/509; 62/510 |
Current CPC
Class: |
F25B 2400/075 20130101;
F25D 11/022 20130101; F25B 5/02 20130101; F25B 47/022 20130101;
F25D 21/006 20130101; F25B 41/20 20210101; A47F 3/0482 20130101;
F25B 2400/22 20130101; F25B 1/10 20130101; F25B 2400/13
20130101 |
Class at
Publication: |
62/81 ; 62/510;
62/156; 62/509; 165/62 |
International
Class: |
F25B 41/00 20060101
F25B041/00; F25B 1/10 20060101 F25B001/10; F25D 21/06 20060101
F25D021/06; F25B 39/04 20060101 F25B039/04; F25B 13/00 20060101
F25B013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2007 |
CN |
200710181325.4 |
Claims
1. A medium and low-temperature integrated refrigeration/freezing
system (100), comprising: a medium-temperature compressor (120), a
low-temperature compressor (122), a condenser (124), a reservoir
(126), an intermediate heat exchanger (128), a medium-temperature
evaporator (130), and a low-temperature evaporator (132),
characterized in that said system further comprises: a first
control valve (141); a second control valve (142); a third control
valve (143); a fourth control valve (144); a first adjusting valve
(145); a second adjusting valve (146); a first one-way valve (147);
a second one-way valve (148); a first expansion valve (150); a
second expansion valve (152); and a third expansion valve (154),
which are for switching between a refrigerating cycle operation and
a discharge gas defrosting cycle operation by controlling the
combination of actions between said first, second, third and fourth
control valves.
2. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 1, characterized in that when said first
control valve (141) is opened, said second control valve (142) is
closed, and said fourth control valve (144) is closed to the
refrigerant pipeline of the reservoir, said system performs the
refrigerating cycle operation.
3. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 2, characterized in that when said
system performs the refrigerating cycle operation, the suction
temperature of the low-temperature compressor is adjusted by said
first adjusting valve (145) to lower the discharge temperature of
said low-temperature compressor.
4. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 1, characterized in that when said first
control valve (141) and said second control valve (142) are opened,
and said fourth control valve (144) is closed to the refrigerant
pipeline of the intercooler, said system performs the discharge gas
defrosting operation.
5. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 4, characterized in that when said
system performs the discharge gas defrosting operation, the suction
temperature of said low-temperature compressor is adjusted by said
second adjusting valve (146), so as to lower said discharge
temperature of the low-temperature compressor.
6. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 1, characterized in that when said
system performs the refrigerating cycle operation or the discharge
gas defrosting operation, said medium-temperature compressor and
the low-temperature compressor are both in operation.
7. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 4, characterized in that said
low-temperature evaporator is provided with a temperature sensor,
and relevant parameters of said temperature sensor are preset to
determine the starting time and ending time of the discharge gas
defrosting operation.
8. The medium and low-temperature integrated refrigeration/freezing
system as claimed in claim 1, characterized in that said
medium-temperature compressor can be a medium-temperature
compressor set, said low-temperature compressor can be a
low-temperature compressor set; said medium-temperature evaporator
can be a group of medium-temperature evaporators, and said
low-temperature evaporator can be a group of low-temperature
evaporators.
9. A method for switching between a refrigerating cycle operation
and a discharge gas defrosting operation in a medium and
low-temperature integrated refrigeration/freezing system, said
medium and low-temperature integrated refrigeration/freezing system
comprising at least a medium-temperature compressor, a
low-temperature compressor, a condenser, a reservoir, an
intercooler, a medium-temperature evaporator, a low-temperature
evaporator, and a first control valve, a second control valve, a
third control valve, a fourth control valve, a first adjusting
valve, a second adjusting valve, a first one-way valve, a second
one-way valve, a first expansion valve, a second expansion valve
and a third expansion valve, characterized in that: when said first
control valve is opened and said second valve is closed, and said
fourth valve is closed to the refrigerant pipeline of said
reservoir, the system performs the discharge gas defrosting
operation; and when said first control valve is closed and said
second valve is opened, and said fourth valve is closed to the
refrigerant pipeline of the intercooler, said system performs the
discharge gas defrosting operation.
10. A switching method as claimed in claim 9, characterized in that
when said system performs the refrigerating cycle operation, the
suction temperature of the low-temperature compressor is adjusted
by said first adjusting valve, so as to lower the discharge
temperature of said low-temperature compressor.
11. The switching method as claimed in claim 9, characterized in
that when said system performs the discharge gas defrosting
operation, the suction temperature of the low-temperature
compressor is adjusted by said second adjusting valve, so as to
lower the discharge temperature of said low-temperature
compressor.
12. The switching method as claimed in claim 9, characterized in
that said low-temperature evaporator is provided with a temperature
sensor, and the relevant parameters of said temperature sensor are
preset to determine the starting time and ending time of the
discharge gas defrosting operation.
13. The switching method as claimed in claim 9, characterized in
that said medium-temperature compressor can be a medium-temperature
compressor set, said low-temperature compressor can be a
low-temperature compressor set; said medium-temperature evaporator
can be a medium-temperature evaporator set, and said
low-temperature evaporator can be a low-temperature evaporator
set.
14. A refrigeration system (100) comprising: a first compartment
(200); a second compartment (202); at least one compressor
(120,122) for compressing refrigerant; a heat rejection heat
exchanger (124) for cooling compressed refrigerant from the at
least one compressor; a reservoir (126) for storing condensed
refrigerant; a first expansion device (150) and a first
evaporator(130) in a flow path associated with the first
compartment (200) for expanding refrigerant and cooling the first
compartment; and a second expansion device (152) and second
evaporator (132) in a flow path associated with the second
compartment for expanding the cooled refrigerant and cooling the
second compartment, further characterized by: means for providing:
a normal refrigerating condition in which refrigerant from the
compressors is cooled by the heat rejection heat exchanger, passed
to the evaporators to absorb heat from the compartments, and
returns to the at least one compressor; and a defrost mode wherein:
the heat rejection heat exchanger is bypassed so that compressed
refrigerant is passed to the second evaporator in a reverse
direction to the refrigerating mode to heat to deliver heat to the
second compartment; after heating the second compartment, the
refrigerant passes to the first expansion device and first
evaporator.
15. The system of claim 14 wherein: the heat rejection heat
exchanger and the reservoir are common to the flow path associated
with the first compartment and the flow path associated with the
second compartment.
16. A method for operating the system of claim 14, comprising:
operating in the refrigeration mode; and switching to operation in
the defrost mode.
17. The method of claim 16, wherein: in the defrost mode, the first
evaporator continues to cool the first compartment.
Description
BACKGROUND
[0001] This disclosure relates to a refrigerating/freezing display
cabinet system and, in particular, to a medium and low-temperature
integrated refrigeration/freezing display cabinet system for
displaying foods and/or beverage products.
[0002] Usually, supermarkets and convenience stores are equipped
with various cabinets, and these cabinets can be open type or can
have doors, for the presentation of fresh foods or beverages to
customers and keeping fresh foods or beverages at certain
temperatures. Because the heat-absorbing heat exchanger
("evaporator") within the refrigerating system frosts when the
ambient temperature is close to or below the freezing point of
water, the heat transfer efficiency of the heat exchanger falls and
even the performance of the whole system falls. The most
conventional ways of defrosting include electrical defrosting and
discharge gas defrosting. Electrical defrosting is relatively
simple but its operational efficiency is relatively low, the time
for defrosting is relatively long and the temperature of fresh
foods and beverages would rise during defrosting. Discharge gas
defrosting is more and more used in refrigerating systems
[0003] Generally, all the refrigerating systems comprise at least
the following parts: a compressor, a heat rejection heat exchanger
("condenser"), at least one evaporator combined with a display
cabinet, an expansion valve and suitable refrigerant pipelines
connected with above devices within a closed circulation loop. The
expansion valve is provided upstream along the refrigerant pipeline
relative to the inlet of the evaporator and is used to expand the
liquid refrigerant to a desired lower pressure, wherein the lower
pressure is selected according to the specific refrigerant to enter
the evaporator. Hereinbelow the detailed description is provided
for the refrigerating systems of different temperature levels; FIG.
1 illustrates a block diagram of the structure of a
medium-temperature refrigerating system in the prior art and FIG. 2
illustrates a block diagram of the structure of a low-temperature
freezing system in the prior art. As illustrated in FIG. 1, the
medium-temperature refrigerating system comprises: a compressor 1,
a condenser 2, a reservoir 3, an expansion valve 4 and an
evaporator 5. When a low-temperature and low-pressure gas, as the
refrigerant, is changed into a high-temperature and high-pressure
gas after having been compressed by the compressor 1, the
high-temperature and high-pressure gas enters the condenser 2 for
cooling and becomes a high-temperature and high-pressure liquid
accompanied by a process of heat dissipation, and subsequently, the
high-temperature and high-pressure liquid flows to the expansion
valve 4 after passing through the reservoir 3. As stated above, the
expansion valve 4 can select the desired pressure of the
refrigerant after expansion according to the selected type of the
refrigerant, and the high-temperature and high-pressure liquid is
changed into a low-temperature and low-pressure liquid and gas
two-phase flow by the expansion valve 4 by throttling, and then
after passing through the evaporator 5 such a two-phase flow
becomes a low-temperature and low-pressure gas and absorbs heat
from the air flow to provide the refrigeration effect. Similarly,
in the low-temperature refrigerating system shown in FIG. 2, it
also comprises a compressor 11, a condenser 12, a reservoir 13, an
expansion valve 14, an evaporator 15 and a liquid injection valve
16. In the refrigerant pipeline portion constituted by the
expansion valve 14, the evaporator 15, the compressor 11, the
condenser 12 and the reservoir 13, the operational process of the
low-temperature refrigerating system is similar to that of the
medium-temperature refrigerating system, except that in the
low-temperature refrigerating system, in order to lower the
discharge temperature of the compressor 11, a branch of the
refrigerant pipeline is provided between the compressor 11 and the
reservoir 13, and the liquid injection valve 16 is provided in such
a branch. When the high-temperature and high-pressure liquid is
transformed into the low-temperature and low-pressure gas, heat is
absorbed and the suction temperature of the compressor 11 is
lowered during this process, and thereby lowering the discharge
temperature of the compressor 11 and providing better protection to
the compressor set.
SUMMARY
[0004] However, in the operation of a system using the independent
medium-temperature refrigerating system and low-temperature system,
the refrigeration efficiency is relatively low and the consumption
of energy is relatively high. To overcome these problems, a medium
and low-temperature integrated refrigerating/freezing system has
been developed by Carrier Corporation, in which the originally
independent medium-temperature refrigerating system and
low-temperature system are integrated into a CDU unit, and the
operation efficiency of the whole integrated system is improved by
the optimized design of the structure and the energy exchange
between the two systems. Such an integrated medium and
low-temperature refrigerating/freezing system may improve the
operational stability of the system, takes less space and may be
able to achieve integrated solutions in a "plug and play" manner,
thus saving space for installation and tuning for the customers.
However, how to apply successfully the discharge gas defrosting
(D2D) technology to the integrated medium and low-temperature
refrigerating/freezing system becomes a technical problem to be
solved by the engineers in the field of refrigeration.
[0005] In view of the technical drawbacks in the refrigerating
system of the prior art with respect to the integration of a
medium-temperature refrigerating system and a low-temperature
freezing system, the present disclosure provides a medium and
low-temperature integrated refrigeration/freezing system with the
function of discharge gas defrosting. The refrigeration/freezing
system of the present disclosure may not only improve the
refrigeration efficiency and save energy resources, but also can
switch between the normal operational state and a discharge gas
defrosting state, which may improve the operational stability of
the system.
[0006] According to one aspect of the present disclosure, there is
provided a medium and low-temperature integrated
refrigeration/freezing system with the function of discharge gas
defrosting. A medium-temperature refrigerating system and a
low-temperature freezing system are integrated to apply D2D
technology. The system comprises at least a medium-temperature
compressor, a low-temperature compressor, a condenser, a reservoir,
an intercooler, a medium-temperature evaporator, a low-temperature
evaporator, and four control valves, two adjusting valves, two
one-way valves and three expansion valves; and by controlling the
combination of actions between these four control valves, the
switching is performed between the refrigerating cycle operation
and the discharge gas defrosting operation
[0007] When the first control valve is opened and the second valve
is closed, and the fourth valve is closed to the refrigerant
pipeline to the reservoir, the medium and low-temperature
integrated system may perform the refrigerating cycle operation.
Further, when the system performs the refrigerating cycle
operation, the suction temperature of the low-temperature
compressor may be adjusted by the first adjusting valve, so as to
lower the discharge temperature of the low-temperature
compressor.
[0008] When the first control valve is closed and the second valve
is opened, and the fourth valve is closed to the refrigerant
pipeline to the intercooler, the system may perform the discharge
gas defrosting operation. Further, when the system performs the
discharge gas defrosting operation, the suction temperature of the
low-temperature compressor may be adjusted by the second adjusting
valve, so as to lower the discharge temperature of the
low-temperature compressor.
[0009] When the system performs the refrigerating cycle operation
or the discharge gas defrosting operation, the medium-temperature
compressor and the low-temperature compressor may be both in
operation.
[0010] According to another aspect of the present disclosure, there
is provided a method for switching between the refrigerating cycle
operation and the discharge gas defrosting operation in a medium
and low-temperature integrated refrigeration/freezing system. The
medium and low-temperature integrated refrigeration/freezing system
comprises at least a medium-temperature compressor, a
low-temperature compressor, a condenser, a reservoir, an
intercooler, a medium-temperature evaporator, a low-temperature
evaporator, and four control valves, two adjusting valves, two
one-way valves and three expansion valves, and by using the
combination of actions between these four control valves the
switching between the refrigerating cycle operation and the
discharge gas defrosting operation is performed. More particularly,
when the first control valve is opened and the second valve is
closed, and the fourth valve is closed to the refrigerant pipeline
to the reservoir, the medium and low-temperature integrated system
performs the refrigerating cycle operation; and when the first
control valve is closed and the second valve is opened, and the
fourth valve is closed to the refrigerant pipeline to the
intercooler, the medium and low-temperature integrated system
performs the discharge gas defrosting operation.
[0011] When the system performs the refrigerating cycle operation,
the suction temperature of the low-temperature compressor may be
adjusted by the first adjusting valve, so as to lower the discharge
temperature of the low-temperature compressor.
[0012] When the system performs the discharge gas defrosting
operation, the suction temperature of the low-temperature
compressor may be adjusted by the second adjusting valve, so as to
lower the discharge temperature of the low-temperature
compressor.
[0013] The low-temperature evaporator may be provided with a
temperature sensor, and the relevant parameters of said temperature
sensor may be preset to determine the starting time and ending time
of the discharge gas defrosting operation.
[0014] By using of the medium and low-temperature integrated
refrigeration/freezing system of the present disclosure, it not
only can perform normal refrigerating cycle operation and discharge
gas defrosting operation based on a medium-temperature compressor
set and a low-temperature compressor set, but also it can improve
the operational efficiency of the whole integrated system by using
the heat exchange between the medium-temperature refrigerating
system and the low-temperature freezing system. Additionally, a
temperature sensor may be fitted in the low-temperature evaporator
and the starting time and ending time of the discharge gas
defrosting can be determined quickly through the intelligent
control of relevant parameters. After the low-temperature
evaporator is optimized by redesign, the defrosting time can be
reduced and the defrosting can be performed thoroughly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Various aspects of the present disclosure will be more
apparent to readers after reading the embodiments of the present
disclosure with reference to the accompanied drawings, in
which:
[0016] FIG. 1 is a block diagram of the principles of the structure
of a medium-temperature refrigerating system in the prior art;
[0017] FIG. 2 is a block diagram of the principles of the structure
of a low-temperature freezing system in the prior art;
[0018] FIG. 3A shows a schematic diagram of the structure of a
discharge gas defrosting system in performing normal refrigerating
cycle, and FIG. 3B shows a schematic diagram of the structure of
the discharge gas defrosting system in performing discharge gas
defrosting;
[0019] FIG. 4 shows a schematic diagram of the structure of a
medium and low-temperature integrated refrigeration/freezing
system;
[0020] FIG. 5 shows a schematic diagram of the structure of a
medium and low-temperature integrated refrigeration/freezing system
with the function of discharge gas defrosting according to one or
more aspects of the present disclosure;
[0021] FIG. 6 shows a schematic diagram of the principles of the
medium and low-temperature integrated refrigeration/freezing system
shown in FIG. 5 in a normal operational state; and
[0022] FIG. 7 shows a schematic diagram of the principles of the
medium and low-temperature integrated refrigeration/freezing system
shown in FIG. 5 in a discharge gas defrosting state.
[0023] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0024] Particular embodiments of the present disclosure shall be
described in more detail with reference to the accompanied
drawings.
[0025] FIG. 3A shows a schematic structural diagram of a discharge
gas defrosting system in performing normal refrigerating cycle and
FIG. 3B shows a schematic structural diagram of a discharge gas
defrosting system in performing discharge gas defrosting. Referring
to FIGS. 3A and 3B, the discharge gas defrosting system mainly
comprises a medium-temperature compressor 21, a low-temperature
compressor 22, a medium-temperature evaporator 31, a
low-temperature evaporator 30 and control valves 41 to 45. In FIGS.
3A and 3B, the parts shown by respective dash lines represent the
refrigerant pipelines not involved in the cycles of the respective
operational states, while the parts shown by respective solid lines
represent the refrigerant pipelines involved in the cycles of the
respective operational states. It can be seen in FIG. 3A that when
the system is performing the normal refrigerating cycle, after the
low-temperature and low-pressure refrigerant has been compressed by
the medium-temperature compressor and the low-temperature
compressor, the control valve 41 is open and the high-temperature
and high-pressure gas discharged from the medium-temperature
compressor 21 and the low-temperature compressor 22 is transmitted
to the condenser (not shown) and then returns to respective
compressors via the medium-temperature evaporator 31 and the
low-temperature evaporator 30.
[0026] After the high-temperature and high-pressure liquid is
transformed into low-temperature and low-pressure gas by the
low-temperature evaporator 30, the suction temperature of the
low-temperature compressor 22 is adjusted by the control valve 44
by throttling, thereby the discharge temperature of the
low-temperature compressor 22 is lowered and the compressor 22 is
better protected.
[0027] It can be seen in FIG. 3B that when the system performs the
discharge gas defrosting operation, the control valve 41 is shut
(to block flow to the condenser) and the low-temperature and
low-pressure refrigerant is changed into the high-temperature and
high-pressure gas after having been processed by the
medium-temperature compressor 21 and low-temperature compressor 22,
enters the low-temperature evaporator via the control valves 42 and
43, is changed into the high-temperature and high-pressure liquid
after having condensed in parts of the refrigerant pipelines of the
system, and finally returns via the medium-temperature evaporator
to the medium-temperature compressor and to the low-temperature
compressor (via the control valves 44 and 45). It should be
understood by those skilled in the art that an expansion valve can
also be added at the intake of the medium-temperature evaporator 31
to change the high-temperature and high-pressure liquid into a
low-temperature and a low-pressure liquid and gas two-phase flow by
throttling, which changes into the low-temperature and low-pressure
gas after having passed through the evaporator and absorbs heat
from the air flow to produce the refrigeration effects.
[0028] FIG. 4 shows a schematic structural diagram of a medium and
low-temperature integrated refrigeration/freezing system. Referring
to FIG. 4, in the medium and low-temperature integrated
refrigeration/freezing system, the original independent
medium-temperature system and low-temperature system of FIGS. 1 and
2 are integrated into a CDU unit 20, in which the performance of
the integrated system is improved by the heat exchange between the
medium-temperature system and the low-temperature system. The
integrated system mainly comprises: a medium-temperature compressor
21, a low-temperature compressor 22, a heat rejection heat
exchanger (condenser) 23, a reservoir 24, an expansion device
(valve) 25, an intercooler 26, an adjusting valve 27, expansion
devices (valves) 28 and 29, a low-temperature heat absorption heat
exchanger (evaporator) 30 and a medium-temperature evaporator 31.
Furthermore, the condenser 23 combines the cooling function of the
condenser in the independent medium-temperature system and that of
the condenser in the independent low-temperature system, and the
reservoir 24 replaces the respective reservoirs of the independent
medium-temperature system and of the independent low-temperature
system. The intercooler 26 and the expansion valve 25 are used to
adjust the subcooling at the low temperature to improve the overall
performance of the system. Although shown connected to a single
medium temperature evaporator and cabinet and a single low
temperature evaporator and cabinet, a given CDU may be connected to
multiple such medium temperature evaporators and/or cabinets and/or
multiple low temperature evaporators and/or cabinets. Also, each
CDU may have multiple such medium temperature compressors and/or
low temperature compressors in respective compressor sets.
[0029] A brief introduction to the operational principles of the
integrated system is: the low-temperature and low-pressure
refrigerant is changed into a high-temperature and high-pressure
gas after having been compressed by the medium-temperature
compressor 21 and the low-temperature compressor 22; the
high-temperature and high-pressure gas changes into
high-temperature and high-pressure liquid after having entered the
condenser 23 and dissipated a large quantity of heat. After passing
through the reservoir 24, the refrigerant is divided into three
pipelines or branches: in the first pipeline 51 it is changed into
a low-temperature and low-pressure liquid and gas two-phase flow by
throttling by the expansion valve 29, is changed into a
low-temperature and low-pressure gas after having entered the
medium-temperature evaporator 31 and absorbed heat to provide the
refrigeration effects, and then returns to the medium-temperature
compressor 21; in the second pipeline 52 it is changed into a
low-temperature and low-pressure liquid and gas two-phase flow by
precooling by the intercooler 26 and throttling by the expansion
valve 28, changes into a low-temperature and low-pressure gas after
having entered the low-temperature evaporator 30 and absorbed heat
to produce the refrigeration effects, and then returns to the
low-temperature compressor 22; and in the third pipeline/branch 54
it passes through the expansion valve 25 and the intercooler 26
(where it absorbs heat from the flow in the second pipeline 52) to
adjust the subcooling at the low temperature, and the refrigerant
returns to the medium-temperature compressor 21 after having been
subcooled, and then returns to the low-temperature compressor 22
after the suction temperature at the low-temperature level is
adjusted via the adjusting valve 27 which sets the balance of flow
between branches (sub-branches) 54-1 and 54-2. It can be seen that
in the integrated system, by using the subcooled liquid-supplying
temperature at the low-temperature level at the intermediate heat
exchanger (the intercooler 26), the efficiency of the
low-temperature level is improved by the energy transfer. It is
shown by experiment data that the energy efficiency ratio of the
low-temperature level is 1.1 and that of the medium-temperature
level is 2.2. Thus, the performance of the whole integrated system
and the operational stability of the medium and low-temperature
systems can be improved by the heat exchange between the
medium-temperature system and the low-temperature system.
[0030] FIG. 5 shows a schematic structural diagram of a medium and
low-temperature integrated refrigeration/freezing system 100 with
the function of discharge gas defrosting and having a CDU 102
coupled to a low temperature cabinet 202 and a medium temperature
cabinet 200. Referring to FIG. 5, in comparison with the medium and
low-temperature integrated refrigeration/freezing system shown in
FIG. 4, the medium and low-temperature integrated
refrigeration/freezing system 100 with the function of discharge
gas defrosting of the present disclosure introduces an operational
process for discharge gas defrosting and it can ensure the
switching between the normal operational state and the discharge
gas defrosting state in the medium and low-temperature integrated
system by controlling relevant valves (under control of a control
system (e.g., a microcontroller) (not shown)).
[0031] Particularly, the integrated system shown in FIG. 5 mainly
comprises: a medium-temperature compressor 120, a low-temperature
compressor 122, a condenser 124, a reservoir 126, an intercooler
128, a medium-temperature evaporator 130, a low-temperature
evaporator 132, control valves 141-144, adjusting valves 145 and
146, one-way valves (check valves) 147 and 148, and expansion
devices (valves) 150, 152, 154.
[0032] The condenser combines simultaneously both the cooling
functions of the condenser in the independent medium-temperature
system and the condenser in the independent low-temperature system,
and the reservoir has replaced the respective reservoirs of the
independent medium-temperature system and of the independent
low-temperature system. The switching between the normal
operational state and the discharge gas defrosting state can be
realized by controlling the combination of actions between control
valves 141-144, and the suction status of the low-temperature
system in the normal operational state and the discharge gas
defrosting state can be adjusted by the adjusting valves 145 and
146, so as to lower the suction temperature of the low-temperature
compressor, and to lower the discharge temperature of the
low-temperature compressor to better ensure the stable operation of
the low-temperature compressor set.
[0033] FIG. 6 shows a schematic diagram of the principles of the
medium and low-temperature integrated refrigeration/freezing system
shown in FIG. 5 in its normal operational state. Here, the parts
shown by the dashed lines in FIG. 6 represent the refrigerant
pipelines not involved in circulation during the normal operation,
while the parts shown by the solid lines represent the refrigerant
pipelines involved in the circulation during the normal operation.
The system has pipelines (branches) 160, 162, and 164 (including
sub-branches 164-1 and 164-2) that are similarly configured and
perform similar functions to the corresponding pipelines or
branches 50, 52, 54 of FIG. 4. An additional pipeline/branch 166 is
provided between a location along the main flowpath 167 downstream
of the condenser 22 and upstream of the intercooler 26 to the
pipeline/branch 162 downstream of the intercooler at the control
valve 144 for recirculating refrigerant in the defrost mode
(discussed below).
[0034] Similarly, a pipeline/branch 168 is provided from a location
downstream of the compressors 120 and 122 to upstream of the low
temperature compressor 122. The control valves 142 and 143 are
respectively positioned along the pipeline/branch 168 for diverting
compressed refrigerant in the defrost mode (discussed below). The
adjusting valve 146 is along a bypass pipeline/flowpath 170 joining
the suction conditions of the two compressors. The one-way valve
147 is along a bypass pipeline/flowpath 172 in parallel with the
expansion valve 152.
[0035] When the integrated system 100 is in the normal operational
state, the control valve 142 is set (shut off) to prevent flow
along the pipeline/flowpath branch 168 and the one-way valve 147 is
in a closed condition, and the control valve 14 is set to block
flow along the pipeline/branch flowpath 166 while permitting flow
along the pipeline/branch 162 from the intercooler 128 to the
expansion valve 152 and low temperature evaporator 132. The
low-temperature and low-pressure refrigerant is changed into the
high-temperature and high-pressure gas after having been compressed
by the medium-temperature compressor 120 and the low-temperature
compressor 122, the high-temperature and high-pressure gas enters
the condenser 124 via the control valve 141 for cooling and becomes
a high-temperature and high-pressure liquid accompanied by a
process of heat dissipation; then the high-temperature and
high-pressure liquid is divided into three pipelines 160, 162, 164
after having passed through the one-way valve 148 and the reservoir
126, and the detailed operations of the three pipelines have been
described above with respect to FIG. 4 and shall not be further
repeated here.
[0036] FIG. 7 shows a schematic diagram of the medium and
low-temperature integrated refrigeration/freezing system of FIG. 5
in the discharge gas defrosting state. Similarly, in FIG. 7, parts
shown by the dash lines represent the refrigerant pipelines not
involved in the circulation during the discharge gas defrosting,
while the parts shown by the solid lines represent the refrigerant
pipelines involved in the circulation during the discharge gas
defrosting. Particularly, when the integrated system is in the
discharge gas defrosting state, the control valve 141 is shut
off/closed, the one-way valve 148 is in a closed condition and the
expansion valves 152 and 154 are shut off/closed, the control valve
142 is open (to permit flow along the branch 168) and the one-way
valve 147 is in an open condition.
[0037] Referring to FIG. 7, the system's operation principles
during the discharge gas defrosting is also described according to
the refrigerant's direction of flow: the low-temperature and
low-pressure refrigerant, exits the medium temperature evaporator
130 and enters into the medium-temperature compressor 120 and, via
the adjusting valve 146, into the low-temperature compressor. The
refrigerant is compressed, by the compressors, is changed into the
high-temperature and high-pressure gas, enters the low-temperature
evaporator 132 (in a reverse of the refrigerant direction) via the
control valves 142 and 143. The refrigerant then enters the
expansion valve 150 via the one-way valve 147 (bypassing the
expansion valve), the control valve 144 and the reservoir 126, and
returns to the compressor set via the medium-temperature evaporator
130 after having been transformed into a low-temperature and
low-pressure liquid and gas two-phase flow by throttling in the
expansion valve 150. During the process of discharge gas
defrosting, the use of a condenser is not involved in any one of
the refrigerant pipelines. To further improve the efficiency of the
discharge gas defrosting and to reduce the time of the discharge
gas defrosting, a temperature sensor (not shown) may be embedded in
the low-temperature evaporator and the starting time and ending
time of the discharge gas defrosting can be determined quickly by
the intelligent control of relevant parameters by the control
system (controller). In a reengineering from the FIG. 4 baseline,
after the low-temperature evaporator is optimized by redesign, the
time of defrosting can be reduced and the defrosting can be
performed thoroughly.
[0038] It should be understood by a person skilled in the art that
the above-mentioned compressors, medium-temperature compressors and
low-temperature compressors are also applicable to compressor sets,
medium-temperature compressor sets and low-temperature compressor
sets. Therefore, the embodiments according to one or more aspects
of the present disclosure are not limited to the cases of a
compressor, a medium-temperature compressor and a low-temperature
compressor.
[0039] The embodiments of the present disclosure are described
above with reference to the accompanied drawings. However,
modifications and variations of the embodiment can be made by those
skilled in the art without departing from the spirit and scope of
the present disclosures. And these modifications and variations
fall within the scope of the present disclosure as defined in the
claims.
[0040] Although an embodiment is described above in detail, such
description is not intended for limiting the scope of the present
disclosure. It will be understood that various modifications may be
made without departing from the spirit and scope of the disclosure.
For example, when implemented in the reengineering of an existing
container configuration, details of the existing configuration may
influence or dictate details of any particular implementation.
Accordingly, other embodiments are within the scope of the
following claims.
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