U.S. patent application number 12/302478 was filed with the patent office on 2009-11-19 for refrigeration system.
Invention is credited to Azuma Kondo, Kazuyoshi Nomura, Yoshinari Oda, Masaaki Takegami, Kenji Tanimoto.
Application Number | 20090282848 12/302478 |
Document ID | / |
Family ID | 38778530 |
Filed Date | 2009-11-19 |
United States Patent
Application |
20090282848 |
Kind Code |
A1 |
Takegami; Masaaki ; et
al. |
November 19, 2009 |
REFRIGERATION SYSTEM
Abstract
In a refrigerant circuit (20), an air conditioning unit (12), a
cold-storage showcase (13), and a freeze-storage showcase (14) are
connected in parallel to an outdoor unit (11). When placing an
indoor heat exchanger (71) of the air conditioning unit (12) in the
thermo-off state, a degree-of-opening control means (101) provides
control so that an indoor expansion valve (72) is placed in the
fully closed state. Thereafter, the degree-of-opening control means
(101) detects the accumulated amount of refrigerant within the
indoor heat exchanger (71) and then adjusts the degree of opening
of the indoor expansion valve (72) depending on the refrigerant
amount detected.
Inventors: |
Takegami; Masaaki; (Osaka,
JP) ; Nomura; Kazuyoshi; (Osaka, JP) ; Kondo;
Azuma; (Osaka, JP) ; Oda; Yoshinari; (Osaka,
JP) ; Tanimoto; Kenji; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
38778530 |
Appl. No.: |
12/302478 |
Filed: |
May 25, 2007 |
PCT Filed: |
May 25, 2007 |
PCT NO: |
PCT/JP2007/060688 |
371 Date: |
November 25, 2008 |
Current U.S.
Class: |
62/222 ;
62/238.6 |
Current CPC
Class: |
F25B 2313/0314 20130101;
F25B 2600/2513 20130101; F25B 2313/0231 20130101; F25B 2313/0233
20130101; F25B 2400/22 20130101; F25B 1/10 20130101; F25B 2700/04
20130101; F25B 2400/19 20130101; F25B 13/00 20130101; F25B
2313/02743 20130101; F25B 2400/0751 20130101 |
Class at
Publication: |
62/222 ;
62/238.6 |
International
Class: |
F25B 41/04 20060101
F25B041/04; F25B 27/00 20060101 F25B027/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2006 |
JP |
2006-146923 |
Claims
1. A refrigeration system including a refrigerant circuit, the
refrigerant circuit being configured such that a plurality of
utilization side units are connected in parallel to a heat source
side unit having a compressor and a heat source side heat
exchanger, wherein at least one of the plurality of utilization
side units includes a heating heat exchanger capable of a heating
operation in which heat is released from refrigerant and an
expansion valve associated with the heating heat exchanger, the
refrigeration system including degree-of-opening control means for
performing: (a) when placing the heating heat exchanger in the
out-of-operation state, a first control operation of reducing the
degree of opening of the expansion valve to such an extent that the
expansion valve is either fully closed or very slightly opened; and
(b) after the completion of the first control operation, a second
control operation of adjusting, based on an index indicative of the
accumulated amount of refrigerant within the heating heat
exchanger, the degree of opening of the expansion valve.
2. The refrigeration system of claim 1, wherein the first control
operation of the degree-of-opening control means is an operation to
place the expansion valve in the fully closed state.
3. The refrigeration system of either claim 1 or claim 2, wherein,
in the second control operation of the degree-of-opening control
means, either the degree of refrigerant subcooling on the inlet
side of the heating heat exchanger or the degree of refrigerant
subcooling within the heating heat exchanger serves as the index
indicative of the accumulated amount of refrigerant within the
heating heat exchanger.
4. The refrigeration system of claim 3, wherein, in the second
control operation of the degree-of-opening control means, the
expansion valve is forcibly opened if the expansion valve remains
in the fully closed state for longer than a predetermined length of
time.
5. The refrigeration system of claim 1, wherein the utilization
side units other than the one that is provided with the heating
heat exchanger each include a respective refrigeration heat
exchanger capable of a refrigeration operation in which refrigerant
absorbs heat from air; wherein the refrigerant circuit is
configured to be capable of a heat recovery operation in which
refrigerant delivered out from the compressor dissipates heat in
the heating heat exchanger, absorbs heat in the refrigeration heat
exchanger, and then is drawn into the compressor; and wherein there
is provided operation control means which provides control so that
the heat recovery operation is temporarily carried out if, in the
second control operation of the degree-of-opening control means,
the index indicative of the accumulated amount of refrigerant
within the heating heat exchanger continues to be in excess of a
specified value for longer than a predetermined length of time.
Description
TECHNICAL FIELD
[0001] This invention generally relates to a refrigeration system
having a plurality of utilization side units and more particularly
to the prevention of the accumulation of refrigerant
("refrigerant's falling-asleep" in the industry jargon) in a
heating heat exchanger placed out of operation.
BACKGROUND ART
[0002] In the past, various refrigeration systems that perform a
refrigeration cycle by the circulation of refrigerant have widely
been applied to air conditioning systems and other like systems.
There is known, as such a type of refrigeration system, a so-called
multi-type refrigeration system in which a plurality of utilization
side units are connected in parallel to a heat source side
unit.
[0003] For example, JP-A-1996-159590 (hereinafter referred to as
the patent document) shows a refrigeration system which includes a
single heat source side unit having a compressor and a heat source
side heat exchanger, and two utilization side units each having a
utilization side heat exchanger (heating heat exchanger) and an
expansion valve.
[0004] In the refrigeration system of the patent document, each
expansion valve is opened at a predetermined degree of opening,
thereby making it possible for each utilization side heat exchanger
to individually carry out a space heating operation. More
specifically, for example, in the case where these two utilization
side units perform respective space heating operations at the same
time, both the expansion valves are placed in the opened state so
that refrigerant is fed to both the utilization side heat
exchangers. As a result, heat is released from the refrigerant
flowing through each utilization side heat exchanger to the indoor
air and each utilization side heat exchanger performs a heating
operation. As a result, indoor spaces respectively corresponding to
the utilization side heat exchangers are heated. On the other hand,
for example, in the case where space heating is carried out by one
of the utilization side units, it is arranged such that the
expansion valve associated with the one utilization side unit to be
placed in operation is opened while the expansion valve associated
with the other utilization side unit to be placed out of operation
is closed. As a result of such arrangement, refrigerant is fed only
to the utilization side unit in operation and only this utilization
side heat exchanger provides indoor space heating.
DISCLOSURE OF THE INVENTION
Problems that the Invention Intends to Overcome
[0005] Incidentally, if, as described above, one of the expansion
valves is closed in order to place its associated utilization side
unit in the out-of-operation state (the so-called thermo-off
state), this causes the possibility that there will occur a
phenomenon (known in the art as a phenomenon of "refrigerant's
falling-asleep"). More specifically, in such a phenomenon,
refrigerant condenses in the utilization side heat exchanger placed
in the out-of-operation state, resulting in the accumulation of
condensed liquid refrigerant therein. And if, as described above,
the refrigerant accumulates in large amounts within one of the
utilization side heat exchangers, the supply of refrigerant to the
other utilization side unit becomes scant. This gives rise to the
problem that the other utilization side unit degrades in
refrigeration capacity or heating capacity.
[0006] In view of the above problems with the prior art, the
present invention was made. Accordingly, an object of the present
invention is to ensure the prevention of any accumulation
("falling-asleep") of refrigerant within a utilization side heat
exchanger placed in the out-of-operation state.
Means for Overcoming the Problems
[0007] The present invention provides, as a first aspect, a
refrigeration system including a refrigerant circuit, the
refrigerant circuit being configured such that a plurality of
utilization side units (12, 13, 14) are connected in parallel to a
heat source side unit (11) having a compressor (41, 42) and a heat
source side heat exchanger (44), wherein at least one of the
plurality of utilization side units (12, 13, 14) includes a heating
heat exchanger (71) capable of a heating operation in which heat is
released from refrigerant and an expansion valve (72) associated
with the heating heat exchanger. And the refrigeration system
includes a degree-of-opening control means (101) for
performing:
(a) when placing the heating heat exchanger (71) in the
out-of-operation state, a first control operation of reducing the
degree of opening of the expansion valve (72) to such an extent
that the expansion valve (72) is either fully closed or very
slightly opened; and (b) after the completion of the first control
operation, a second control operation of adjusting, based on an
index indicative of the accumulated amount of refrigerant within
the heating heat exchanger (71), the degree of opening of the
expansion valve (72).
[0008] In the first aspect of the present invention, the plurality
of utilization side units (12,13, 14) are connected in parallel to
the heat source side unit (11). This arrangement constitutes a
so-called multi-type refrigeration system. In the refrigerant
circuit (20) of the refrigeration system, a vapor compression
refrigeration cycle is performed by the circulation of refrigerant.
Refrigerant is supplied to each of the utilization side units (12,
13, 14) where it evaporates or condenses, and by these utilization
side units (12, 13, 14), indoor space heating/cooling or showcase
storage compartment refrigeration is separately provided.
[0009] Here, in the present invention, when stopping the heating
heat exchanger (71) capable of performing a heating operation in
which heat is released from the refrigerant, the degree-of-opening
control means (101) first performs a first control operation. In
the first control operation, the degree of opening of the expansion
valve (72) associated with the heating heat exchanger (71) is
reduced to the fully closed degree or to an extremely small degree
as close to the fully closed degree as possible. As a result, since
almost no refrigerant is fed to the heating heat exchanger (71), no
heating operation is carried out in the heating heat exchanger
(71). On the other hand, if the expansion valve (72) is throttled
in such a manner, this causes the refrigerant within the heating
heat exchanger (71) to gradually condense, as a result of which
liquid refrigerant will accumulate within the heating heat
exchanger (71). This results in the occurrence of "refrigerant's
falling-asleep" in the heating heat exchanger (71).
[0010] To cope with the above, after the completion of the first
control operation, the degree-of-opening control means (101) of the
present invention carries out a second control operation in order
to prevent the occurrence of "refrigerant's falling-asleep" in the
heating heat exchanger (71). In the second control operation, the
index indicative of the accumulated amount of refrigerant within
the heating heat exchanger (71) is detected by means of a given
method. And based on the index detected, the degree of opening of
the expansion valve (72) is adequately adjusted. More specifically,
if condensed refrigerant keeps accumulating within the heating heat
exchanger (71) after the completion of the first control operation
and, as a result, the index indicative of the accumulated amount of
refrigerant within the heating heat exchanger (71) increases, then
the degree-of-opening control means (101) provides control so that
the degree of opening of the expansion valve (72) is increased. As
a result, the refrigerant accumulated within the heating heat
exchanger (71) is expelled through the expansion valve (72) to
outside the utilization side unit (12).
[0011] Meanwhile, if, after accomplishing the elimination of
"refrigerant's falling-asleep" in the heating heat exchanger (71)
in the way as described above, the degree of opening of the
expansion valve (72) still remains in the largely opened state,
this means that the supply of refrigerant to the heating heat
exchanger (71) is provided in vain. As a result, the other
utilization side unit (12) is likely to provide poor refrigeration
(heating) capacity. To cope with this, in the second control
operation, if the elimination of "refrigerant's falling-asleep" in
the heating heat exchanger (71) is accomplished and, as a result,
the aforesaid index decreases, then the degree of opening of the
expansion valve (72) is promptly reduced with the aid of the
degree-of-opening control means (101). As a result, the supply of
refrigerant to the heating heat exchanger (71) decreases, whereby
the supply of refrigerant to each of the other utilization side
units (13,14) increases accordingly.
[0012] The present invention provides, as a second aspect according
to the first aspect, a refrigeration system that is characterized
in that the first control operation of the degree-of-opening
control means (101) is an operation to place the expansion valve
(72) in the fully closed state.
[0013] In the second aspect of the present invention, at the time
of the operation that stops the heating heat exchanger (71), the
degree-of-opening control means (101) performs a first control
operation to place the expansion valve (72) in the fully closed
state. As a result, since no refrigerant flows in the utilization
side unit (12) provided with the heating heat exchanger (71), the
supply of refrigerant to each of the other utilization side units
(13,14) increases accordingly.
[0014] The present invention provides, as a third aspect according
to either one of the first and second aspects, a refrigeration
system that is characterized in that, in the second control
operation of the degree-of-opening control means (101), either the
degree of refrigerant subcooling on the inlet side of the heating
heat exchanger (71) or the degree of refrigerant subcooling within
the heating heat exchanger (71) serves as the index indicative of
the accumulated amount of refrigerant within the heating heat
exchanger (71).
[0015] In the third aspect of the present invention, the degree of
refrigerant subcooling is used as the index indicative of the
accumulated amount of refrigerant within the heating heat exchanger
(71). That is, if refrigerant condenses and accumulates in liquid
form within the heating heat exchanger (71) placed in the
out-of-operation state, this liquid refrigerant further dissipates
heat and then enters the subcooling state. Therefore, it is
possible to observe the accumulated amount of refrigerant within
the heating heat exchanger (71) by detecting the degree of
refrigerant subcooling within the heating heat exchanger (71). In
addition, if liquid refrigerant accumulates completely within the
heating heat exchanger (71), there is the possibility that
refrigerant will condense also in the vicinity of the inlet of the
heating heat exchanger (71) and enter the subcooling state.
Therefore, it is possible to observe the accumulated amount of
refrigerant within the heating heat exchanger (71) by detecting the
degree of refrigerant subcooling on the inlet side of the heating
heat exchanger (71).
[0016] The present invention provides, as a fourth aspect according
to the third aspect, a refrigeration system that is characterized
in that, in the second control operation of the degree-of-opening
control means (101), the expansion valve (72) is forcibly opened at
a predefined degree of opening if the expansion valve (72) remains
in the fully closed state for longer than a predetermined length of
time.
[0017] In the fourth aspect of the present invention, the expansion
valve (72) is forcibly opened if it has continuously been placed in
the fully closed state, although the degree of opening of the
expansion valve (72) is normally controlled based on the degree of
refrigerant subcooling by the degree-of-opening control means (101)
during the second control operation.
[0018] Incidentally, in the case where, like the aforesaid third
aspect of the present invention, the degree of refrigerant
subcooling on the inlet side of, or within the heating heat
exchanger (71) is detected, it is impossible, in some cases, to
accurately find the amount of refrigerant within the heating heat
exchanger (71) due to the influence of the ambient temperature of
the heating heat exchanger (71). More specifically, for example,
the saturated temperature corresponding to the pressure of high
pressure gas, Pc, and the temperature of refrigerant on the inlet
side of the heating heat exchanger (71), Th1, are detected by the
specific sensors, and if, when making a calculation of the degree
of subcooling from the temperature difference (the difference
between the temperatures Pc and Th1), the ambient temperature of
the heating heat exchanger (71) is relatively high, then the
temperature, Th1, detected by the sensor, too, tends to be high.
Therefore, under such a condition, the degree of refrigerant
subcooling detected by the sensors decreases, although there
actually is accumulated a large amount of refrigerant within the
heating heat exchanger (71). As a result, there is the possibility
that the expansion valve (72) will continuously remain in the fully
closed state.
[0019] To cope with the above, in the fourth aspect of the present
invention, the expansion valve (72) is forcibly opened if, in the
second control operation, the expansion valve (72) has continuously
been in the fully closed state for longer than a predetermined
length of time. In this case, it is preferred that the degree of
opening of the expansion valve (72) be as minimum as possible. With
this arrangement, that is, by opening the expansion valve (72) in
the above described manner, the elimination of "refrigerant's
falling-asleep" within the heating heat exchanger (71) can be
accomplished without fail, even when the degree of refrigerant
subcooling (Pc-Th1) is detected having a small value due to the
influence of the ambient temperature.
[0020] In addition, when, after the forced opening of the expansion
valve (72) in the above-described way, further adjusting the degree
of opening of the expansion valve (72) with the aid of the
degree-of-opening control means (101), the accurate amount of
refrigerant within the heating heat exchanger (71) can be detected
with ease. That is, if the expansion valve (72) is forcibly opened,
the continuous supply of refrigerant is provided to the heating
heat exchanger (71). As a result, the refrigerant flowing in the
heating heat exchanger (71) is less subject to the ambient
temperature. Therefore, it is avoided that the degree of
refrigerant subcooling is calculated having a low value, in spite
of the occurrence of "refrigerant's falling asleep" within the
heating heat exchanger (71). This therefore makes it possible that,
after the forced opening of the expansion valve (72), the degree of
opening of the expansion valve (72) can be adjusted properly by
accurate detection of the amount of refrigerant within the heating
heat exchanger (71).
[0021] The present invention provides, as a fifth aspect according
to the first aspect, a refrigeration system that is characterized
in that the utilization side units (13, 14) other than the
utilization side unit (12) that is provided with the heating heat
exchanger (71) each include a respective refrigeration heat
exchanger (81, 91) capable of a refrigeration operation in which
refrigerant absorbs heat from air; that the refrigerant circuit
(20) is configured to be capable of a heat recovery operation in
which refrigerant delivered out from the compressor dissipates heat
in the heating heat exchanger (71), absorbs heat in the
refrigeration heat exchanger (81, 91), and then is drawn into the
compressor (41, 42); and that there is provided an operation
control means (102) which provides control so that the heat
recovery operation is temporarily carried out if, in the second
control operation of the degree-of-opening control means (101), the
index indicative of the accumulated amount of refrigerant within
the heating heat exchanger (71) continues to be in excess of a
specified value for longer than a predetermined length of time.
[0022] In the fifth aspect of the present invention, the
refrigeration heat exchangers (81, 91) are disposed respectively in
the utilization side units (13, 14) other than the utilization side
unit (12) that is provided with the heating heat exchanger (71). In
each refrigeration heat exchanger (81, 91), the refrigerant absorbs
heat from air thereby to provide storage-compartment space
refrigeration. In the refrigerant circuit (20) of the refrigeration
system, it is possible to perform a heat recovery operation by the
feeding of refrigerant delivered out from the compressor (41, 42)
to the heating heat exchanger (71) and the refrigeration heat
exchangers (81, 91) in that order and then by the returning of
refrigerant to the intake side of the compressor (41, 42). That is,
in the heat recovery operation, there is performed a refrigeration
cycle in which refrigerant delivered out from the compressor (41,
42) is not fed to the heat source side heat exchanger (44) of the
heat source side unit (11) but is condensed in the heating heat
exchanger (71) while the refrigerant after condensation is pressure
reduced in the expansion valve (72) and then is evaporated in the
refrigeration heat exchanger (81, 82).
[0023] Here, if the elimination of "refrigerant's falling-asleep"
within the heating heat exchanger (71) fails to be accomplished
even after the execution of the second control operation by the
degree-of-opening control means (101), the operation control means
(102) provides control so that the heat recovery operation is
forcibly carried out in the refrigerant circuit (20). This causes
the positive supply of refrigerant to the heating heat exchanger
(71), thereby ensuring that the elimination of "refrigerant's
falling-asleep" within the heating heat exchanger is accomplished.
At the same time, the refrigerant discharged from within the
heating heat exchanger (71) and flowing through the refrigeration
heat exchanger (81, 82) is used for the refrigeration operation of
the refrigeration heat exchanger (81, 82).
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0024] in the first aspect of the present invention, when carrying
out an operation to stop the heating heat exchanger (71), the
degree of opening of the expansion valve (72) is reduced by a first
control operation, which is followed by the execution of a second
control operation to adjust the degree of opening of the expansion
valve (72) based on the index indicative of the accumulated amount
of refrigerant within the heating heat exchanger (71). Therefore,
in accordance with the present invention, it becomes possible that,
upon the detection of the occurrence of "refrigerant's
falling-asleep" within the heating heat exchanger (71), the degree
of opening of the expansion valve (72) is increased, whereby the
refrigerant accumulated within the heating heat exchanger (71) can
be fed to the other utilization side units (13, 14). That is, in
accordance with the present invention, it is ensured that the
elimination of "refrigerant's falling-asleep" within the heating
heat exchanger (71) in the out-of-operation state is accomplished
without fail, thereby making it possible to prevent the other
utilization side units (13, 14) from capacity degradation.
[0025] In addition, in accordance with the present invention, the
degree of opening of the expansion valve (72) can be made small if
the accumulated amount of refrigerant within the heating heat
exchanger (71) is small. Therefore, it is avoided that an excess
supply of refrigerant is provided to the heating heat exchanger
(71) despite the fact that the elimination of "refrigerant's
falling-asleep" within the heating heat exchanger (71) has already
been accomplished. This makes it possible to satisfactorily ensure
the supply of refrigerant to the other utilization side units (13,
14). Accordingly, it becomes possible to still further effectively
prevent the other utilization side units (13, 14) from capacity
degradation.
[0026] In addition, in the second aspect of the present invention,
the first control operation is carried out to place the expansion
valve (72) in the fully closed state, when stopping the heating
heat exchanger (71). Therefore, in accordance with the present
invention, it is possible to further increase the supply of
refrigeration to the other utilization side units (13, 14), thereby
enhancing their capacity.
[0027] In addition, in the third aspect of the present invention,
it is arranged such that, in the second control operation, the
accumulated amount of refrigerant within the heating heat exchanger
(71) is detected using the degree of refrigerant subcooling on the
inlet side of or within the heating heat exchanger (71). As a
result of such arrangement, in accordance with the present
invention, it is possible to easily observe the occurrence of
"refrigerant's falling-asleep" within the heating heat exchanger
(71) with the aid of the temperature sensors, the pressure sensors,
or other like sensors disposed in the refrigerant circuit (20).
[0028] Here, in the fourth aspect of the present invention, in view
of the fact that the degree of refrigerant subcooling decreases due
to the influence of the ambient temperature of the heating heat
exchanger (71), the expansion valve (72) is opened if, in the
second control operation, the expansion valve (72) continues to be
in the fully closed state for longer than a predetermined length of
time. Therefore, in accordance with the present invention, it is
possible to avoid the occurrence of such a condition that the
expansion valve (72) still remains in the closed state although
refrigerant is actually "falling asleep" within the heating heat
exchanger (71). This ensures that the elimination of "refrigerant's
falling-asleep" within the heating heat exchanger (71) is
accomplished without fail.
[0029] In addition, in the fourth aspect of the present invention,
after the expansion valve (72) is opened to allow the flow of
refrigerant through the heating heat exchanger (71), the degree of
opening of the expansion valve (72) can further be controlled
depending on the degree of refrigerant subcooling. As a result of
such arrangement, the temperature of refrigerant flowing on the
inflow side of the heating heat exchanger (71) or through the
inside of the heating heat exchanger (71) is less subject to the
influence of the ambient temperature of the heating heat exchanger
(71), whereby it becomes possible to accurately detect the amount
of refrigerant within the heating heat exchanger (71).
Consequently, in accordance with the present invention, it is
possible to properly control the degree of opening of the expansion
valve (72) depending on the accumulated amount of refrigerant
within the heating heat exchanger (71). This therefore ensures that
the elimination of "refrigerant's falling-asleep" within the
heating heat exchanger (71) is accomplished without fail and, in
addition, it is possible to satisfactorily ensure the supply of
refrigerant to the other utilization side units (13, 14).
[0030] In the fifth aspect of the present invention, the heat
recovery operation is carried out in the refrigerant circuit (20)
if the elimination of "refrigerant's falling-asleep" within the
heating heat exchanger (71) still remains unaccomplished even after
the execution of the second control operation by the
degree-of-opening control means (101). Therefore, in accordance
with the present invention, the elimination of "refrigerant's
falling-asleep" within the heating heat exchanger (71) can be
accomplished by the feed-in of refrigerant to the heating heat
exchanger (71). At this time, in the present invention, the
refrigerant delivered out from the compressor (41, 42) will not be
fed into the heat source side heat exchanger (44) and others, but
will be positively fed into the heating heat exchanger (71).
Therefore, in accordance with the present invention, it is ensured
that the refrigerant within the heating heat exchanger (71) is
expelled outside.
[0031] In addition, in the heat recovery operation, refrigerant is
evaporated in each of the refrigeration heat exchangers (81, 91)
while the accumulated refrigerant within the heating heat exchanger
(71) is being expelled outside. That is, the present invention
ensures that the elimination of "refrigerant's falling-asleep"
within the heating heat exchanger (71) can be accomplished without
the stop of the refrigeration operation by each of the
refrigeration heat exchangers (81, 91).
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In the drawings:
[0033] FIG. 1 is a plumbing diagram of a refrigerant circuit in a
refrigeration system according to an embodiment of the present
invention;
[0034] FIG. 2 is a plumbing diagram illustrating the flow of
refrigerant during the space cooling operation;
[0035] FIG. 3 is a plumbing diagram illustrating the flow of
refrigerant during the space heating operation;
[0036] FIG. 4 is a plumbing diagram illustrating the flow of
refrigerant immediately after the thermo-off operation of an indoor
heat exchanger;
[0037] FIG. 5 is a flowchart illustrating a second control
operation by a degree-of-opening control means;
[0038] FIG. 6 is a flowchart illustrating the operation of control
by an operation control means; and
[0039] FIG. 7 is a plumbing diagram illustrating the flow of
refrigerant during the heat recovery operation.
REFERENCE NUMERALS IN THE DRAWINGS
[0040] In the drawings: [0041] 10 refrigeration system [0042] 12
air conditioning unit (utilization side unit) [0043] 13
cold-storage showcase (utilization side unit) [0044] 14
freeze-storage showcase (utilization side unit) [0045] 20
refrigerant circuit [0046] 41 first compressor [0047] 42 second
compressor [0048] 71 indoor heat exchanger (heating heat exchanger)
[0049] 72 indoor expansion valve (expansion valve) [0050] 81
cold-storage heat exchanger (refrigeration heat exchanger) [0051]
91 freeze-storage heat exchanger (refrigeration heat exchanger)
[0052] 101 degree-of-opening control means 102 operation control
means
BEST MODE FOR CARRYING OUT THE INVENTION
[0053] Hereinafter, with reference to the accompanying drawings,
preferred embodiments of the present invention will be described in
detail.
[0054] A refrigeration system (10) according to the present
embodiment is of the type for the installation in a convenience
store or other facility. The refrigeration system (10) provides, at
the same time, refrigeration to a cold-storage compartment and a
freeze-storage compartment and air conditioning to an indoor
space.
[0055] As shown in FIG. 1, the refrigeration system (10) includes
an outdoor unit (11), an air conditioning unit (12), a cold-storage
showcase (13), and a freeze-storage showcase (14). The outdoor unit
(11) is provided with an outdoor circuit (40) which constitutes a
heat source side circuit. The air conditioning unit (12) is
provided with an air conditioning circuit (70) which constitutes a
first utilization side circuit. The cold-storage showcase (13) is
provided with a cold-storage circuit (80) which constitutes a
second utilization side circuit. The freeze-storage showcase (14)
is provided with a freeze-storage circuit (90) which constitutes a
third utilization side circuit. In the refrigeration system (1),
these utilization side circuits (70, 80, 90) are connected in
parallel to the outdoor circuit (40) thereby to constitute a
refrigerant circuit (20) which performs a vapor compression
refrigeration cycle.
[0056] The outdoor circuit (40) and each utilization side circuit
(70, 80, 90) are connected together by liquid side interunit piping
(31), first gas side interunit piping (32), and second gas side
interunit piping (33). One end of the liquid side interunit piping
(31) is connected to a liquid side closing valve (21) of the
outdoor circuit (40). The other end of the liquid side interunit
piping (31) diverges into three branches, namely a first liquid
branch pipe (31a), a second liquid branch pipe (31b), and a third
liquid branch pipe (31c). The first to third liquid branch pipes
(31a, 31b, 31c) are connected to the air conditioning circuit (70),
to the cold-storage circuit (80), and to the freeze-storage circuit
(90), respectively. One end of the first gas side interunit piping
(32) is connected to a first gas side closing valve (22) of the
outdoor circuit (40) and the other end thereof is connected to the
air conditioning circuit (70). One end of the second gas side
interunit piping (33) is connected to a second gas side closing
valve (23) of the outdoor circuit (40). The other end of the second
gas side interunit piping (33) diverges into two branches, namely a
first gas branch pipe (33a) and a second gas branch pipe (33b). The
first and second gas branch pipes (33a, 33b) are connected to the
cold-storage circuit (80) and to the freeze-storage circuit (90),
respectively.
Outdoor Unit
[0057] The outdoor circuit (40) of the outdoor unit (11) includes
three (first to third) compressors (41, 42, 43), an outdoor heat
exchanger (44), a receiver (45), an outdoor expansion valve (46),
and three (first to third) four-way selector valves (47, 48,
49).
[0058] The first to third compressors (41, 42, 43) are each formed
by a respective scroll compressor of the high pressure dome type.
The first compressor (41) constitutes a compressor of the variable
capacity type. That is, the first compressor (41) is configured
such that its speed of rotation is made variable by inverter
control. On the other hand, the second and third compressors (42,
43) each constitute a compressor of the fixed capacity type, that
is, whose speed of rotation is fixed.
[0059] Connected to the intake side of the first compressor (41) is
one end of a first intake pipe (51). The other end of the first
intake pipe (51) is connected to the second gas side closing valve
(23). Connected to the intake side of the second compressor (42) is
one end of a second intake pipe (52). The other end of the second
intake pipe (52) is connected to the third four-way selector valve
(49). Connected to the intake side of the third compressor (43) is
one end of a third intake pipe (53). The other end of the third
intake pipe (53) is connected to the second four-way selector valve
(48).
[0060] Connected to the delivery side of the first compressor (41)
is one end of a first delivery pipe (54). The other end of the
first delivery pipe (54) is connected through delivery piping (57)
to the first four-way selector valve (47). Connected to the
delivery side of the second compressor (42) is one end of a second
delivery pipe (55). The other end of the second delivery pipe (55)
is connected to the delivery piping (57). Connected to the delivery
side of the third compressor (43) is one end of a third delivery
pipe (56). The other end of the third delivery pipe (56) is
connected in the middle of the delivery piping (57).
[0061] The outdoor heat exchanger (44) is a fin-and-tube heat
exchanger of the cross fin type, and constitutes a heat source side
heat exchanger. There is arranged in the vicinity of the outdoor
heat exchanger (44) an outdoor fan (50). In the outdoor heat
exchanger (44), the exchange of heat takes place between the
outdoor air distributed by the outdoor fan (50) and the
refrigerant. One end of the outdoor heat exchanger (44) is
connected to the first four-way selector valve (47). The other end
of the outdoor heat exchanger (44) is connected through a first
liquid pipe (58) to the top of the receiver (45). The bottom of the
receiver (45) is connected through a second liquid pipe (59) to the
liquid side closing valve (21).
[0062] One ends of first and second bypass pipes (60, 61) are
connected in the middle of the first liquid pipe (58). The other
ends of the first and second bypass pipes (60, 62) are each
connected to the second liquid pipe (59). The outdoor expansion
valve (46) is disposed in the first bypass pipe (60). The outdoor
expansion valve (46) is formed by an electronic expansion valve
whose degree of opening is adjustable. One end of a liquid
injection pipe (62) is connected in the middle of the second bypass
pipe (61). The other end of the liquid injection pipe (62) is
connected in the middle of the first intake pipe (51). In addition,
the liquid injection pipe (62) is provided with a flow control
valve (63) whose degree of opening is adjustable.
[0063] Each of the first to third four-way selector valves (47, 48,
49) has four (first to fourth) ports. In the first four-way
selector valve (47), its ports are connected as follows: the first
port is connected to the delivery piping (57); the second port is
connected to the fourth port of the second four-way selector valve
(48); the third port is connected to the outdoor heat exchanger
(44); and the fourth port is connected to the first gas side
closing valve (22). In the second four-way selector valve (48), its
ports are connected as follows: the first and second ports are
connected to the third delivery pipe (56) and to the third intake
pipe (53), respectively, while the third port is closed. In the
third four-way selector valve (49), its ports are connected as
follows: the second to fourth ports are connected to the second
intake pipe (52), to the third intake pipe (53), and to the first
intake pipe (51), respectively, while the first port is closed.
[0064] Each of the four-way selector valves (47, 48, 49) is
selectively switchable between a first state (indicated by solid
line in FIG. 1) and a second state (indicated by broken line in
FIG. 1). When in the first state, the first and third ports fluidly
communicate with each other, while the second and fourth ports
fluidly communicate with each other. When in the second state, the
first and fourth ports fluidly communicate with each other, while
the second and third ports fluidly communicate with each other.
[0065] Various sensors and pressure switches are disposed in the
outdoor circuit (40). More specifically, the first intake pipe (51)
is provided with a first intake temperature sensor (111) and a
first intake pressure sensor (112). The third intake pipe (53) is
provided with a second intake temperature sensor (113) and a second
intake pressure sensor (114). The first delivery pipe (54) is
provided with a first high pressure switch (115). The second
delivery pipe (55) is provided with a second high pressure switch
(116). The third delivery pipe (56) is provided with a third high
pressure switch (117). The delivery piping (57) is provided with a
first delivery temperature sensor (118) and a first delivery
pressure sensor (119). The third delivery pipe (56) is provided
with a second delivery temperature sensor (120). The outdoor heat
exchanger (44) is provided, in its heat transfer tube, with an
outdoor side refrigerant temperature sensor (121). In addition,
there is disposed in the vicinity of the outdoor heat exchanger
(44) an outdoor temperature sensor (122).
[0066] In addition, the outdoor circuit (40) is provided with a
plurality of check valves configured to allow refrigerant to flow
in one direction only while stopping the flow of refrigerant in the
opposite direction. More specifically, a check valve (CV-1) is
disposed in piping between the first intake pipe (51) and the
second intake pipe (52). A check valve (CV-2) is disposed in piping
between the second intake pipe (52) and the third intake pipe (53).
In addition, the second delivery pipe (55) is provided with a check
valve (CV-3). The third delivery pipe (56) is provided with a
fourth check valve (CV-4). The first liquid pipe (58) is provided
with a check valve (CV-5). The second liquid pipe (59) is provided
with a check valve (CV-6). The second bypass pipe (61) is provided
with a check valve (CV-7). The check valves (CV-1, CV-2, . . . )
are so configured as to permit only the flow of refrigerant in
directions indicated by arrows assigned to the symbols
representative of these valves in FIG. 1.
Air Conditioning Unit
[0067] The air conditioning circuit (70) of the air conditioning
unit (12) is provided with an indoor heat exchanger (71) and an
indoor expansion valve (72). The indoor heat exchanger (71) is a
fin-and-tube heat exchanger of the cross fin type, and constitutes
a first utilization side heat exchanger. In addition, the indoor
heat exchanger (71) constitutes a heating heat exchanger capable of
a heating operation in which heat is released from the refrigerant.
There is disposed in the vicinity of the indoor heat exchanger (71)
an indoor fan (73). In the indoor heat exchanger (71), the exchange
of heat takes place between the indoor air distributed by the
indoor fan (73) and the refrigerant. The indoor expansion valve
(72) is formed by an electronic expansion valve whose degree of
opening is adjustable by a pulse motor.
[0068] In the air conditioning circuit (70), a first refrigerant
temperature sensor (123) is disposed in piping between the first
gas side interunit piping (32) and the indoor heat exchanger (71)
and a second refrigerant temperature sensor (124) is disposed in
the heat transfer tube of the indoor heat exchanger (71). In
addition, there is disposed in the vicinity of the indoor heat
exchanger (71) an indoor temperature sensor (125).
Cold-Storage Showcase
[0069] The cold-storage circuit (80) of the cold-storage showcase
(13) is provided with a cold-storage heat exchanger (81) and a
cold-storage expansion valve (82). The cold-storage heat exchanger
(81) is a fin-and-tube heat exchanger of the cross fin type, and
constitutes a second utilization side heat exchanger. In addition,
the cold-storage heat exchanger (81) is a refrigeration heat
exchanger in which refrigerant absorbs heat from air for the
provision of refrigeration to the cold-storage compartment. There
is disposed in the vicinity of the cold-storage heat exchanger (81)
a cold-storage fan (83). In the cold-storage heat exchanger (81),
the exchange of heat takes place between the storage compartment
air distributed by the cold-storage fan (83) and the
refrigerant.
[0070] In the cold-storage circuit (80), a first outlet refrigerant
temperature sensor (126) is disposed on the outflow side of the
cold-storage heat exchanger (81). The cold-storage expansion valve
(82) is formed by an expansion valve of the temperature sensing
type whose degree of opening can be adjusted depending on the
temperature detected by the first outlet refrigerant temperature
sensor (126). There is disposed in the vicinity of the upstream
side of the cold-storage expansion valve (82) a first solenoid
valve (SV-1) which is flexible in the degree of opening. In
addition, there is disposed in the vicinity of the cold-storage
heat exchanger (81) a first storage compartment temperature sensor
(127) for the detection of the temperature of storage compartment
air in the cold-storage showcase (13).
Freeze-Storage Showcase
[0071] The freeze-storage circuit (90) of the freeze-storage
showcase (14) is provided with a freeze-storage heat exchanger
(91), a freeze-storage expansion valve (92), and a booster
compressor (94). The freeze-storage heat exchanger (91) is a
fin-and-tube heat exchanger of the cross fin type, and constitutes
a third utilization side heat exchanger. In addition, the
freeze-storage heat exchanger (91) is a refrigeration heat
exchanger in which refrigerant absorbs heat from air for the
provision of refrigeration to the freeze-storage compartment. There
is disposed in the vicinity of the freeze-storage heat exchanger
(91) a freeze-storage fan (93). In the freeze-storage heat
exchanger (91), the exchange of heat takes place between the
storage compartment air distributed by the freeze-storage fan (93)
and the refrigerant.
[0072] In the freeze-storage circuit (90), a second outlet
refrigerant temperature sensor (128) is disposed on the outflow
side of the freeze-storage heat exchanger (91). The freeze-storage
expansion valve (92) is formed by an expansion valve of the
temperature sensing type whose degree of opening can be adjusted
depending on the temperature detected by the second outlet
refrigerant temperature sensor (128). There is disposed in the
vicinity of the upstream side of the freeze-storage expansion valve
(92) a second solenoid valve (SV-2) which is flexible in the degree
of opening. In addition, there is disposed in the vicinity of the
freeze-storage heat exchanger (91) a second storage compartment
temperature sensor (129) for the detection of the temperature of
storage compartment air in the freeze-storage showcase (14).
[0073] The booster compressor (94) is a scroll compressor of the
high pressure dome type, and constitutes a compressor of the
variable capacity type. A fourth intake pipe (95) and a fourth
deliver pipe (96) are connected to the intake side and to the
delivery side of the booster compressor (94), respectively. The
fourth delivery pipe (96) is provided with a fourth high pressure
switch (130), an oil separator (97), and a check valve (CV-8).
Connected to the oil separator (97) is an oil return pipe (98) for
the return of refrigeration oil separated from the refrigerant, to
the intake side of the booster compressor (94). The oil return pipe
(98) is provided with a capillary tube (98a).
[0074] In addition, the freeze-storage circuit (90) is provided
also with a third bypass pipe (99) by which the fourth intake pipe
(95) and the fourth delivery pipe (96) are connected together. The
third bypass pipe (99) is provided with a check valve (CV-9). The
third bypass pipe (99) is configured such that, for example, when
the booster compressor (94) breaks down, the refrigerant flowing in
the fourth intake pipe (95) is made to bypass the booster
compressor (94) and be fed to the fourth delivery pipe (96).
Controller
[0075] The refrigeration system (10) is provided with a controller
(100) for controlling the devices (targets for control) disposed in
the refrigerant circuit (20). The controller (100) is configured
such that it can receive signals from the sensors disposed in the
refrigerant circuit (20). And in response to the signals from the
sensors, the controller (100) controls the operation of each
compressor, the switching of each four-way selector valve and other
operations.
[0076] In addition, the controller (100) is provided with a
degree-of-opening control means (101) and an operation control
means (102) both of which are features of the present invention.
The degree-of-opening control means (101) and the operation control
means (102) together constitute a means for preventing the
accumulation of refrigerant in the indoor heat exchanger (71) when
the heating operation of the indoor heat exchanger (71) is stopped.
The operation of control by the degree-of-opening control means
(101) and the operation of control by the operation control means
(102) will fully be described hereinafter.
Running Operation
[0077] The following is a description of the running operation of
the refrigeration system (10) according to the present embodiment.
In the refrigeration system (10), it is possible to selectively
perform a space cooling operation in which the air conditioning
unit (12) provides indoor space cooling while simultaneously the
storage compartment of each showcase (13, 14) is being
refrigerated, or a space heating operation in which the air
conditioning unit (12) provides indoor space heating while
simultaneously the storage compartment of each showcase (13, 14) is
being refrigerated.
Space Cooling Operation
[0078] Referring now to FIG. 2, a typical space cooling operation
of the refrigeration system (10) will be described below.
[0079] In the space cooling operation of this example, the first
four-way selector valve (47), the second four-way selector valve
(48), and the third four-way selector valve (49) are all placed in
the first state. In addition, the outdoor expansion valve (46) and
the flow control valve (63) are fully closed and the first and
second solenoid valves (SV-1, SV-2) are opened. Furthermore, the
indoor expansion valve (72), the cold-storage expansion valve (82),
and the freeze-storage expansion valve (92) are properly adjusted
in their degree of opening. In addition, the fans (50, 73, 83, 93),
the first to third compressors (41, 42, 43), and the booster
compressor (94) are each placed in operation.
[0080] The flows of refrigerant compressed in the first to third
compressors (41, 42, 43) join together in the delivery piping (57).
Thereafter, the joined flow of refrigerant passes through the first
four-way selector valve (47) and flows through the outdoor heat
exchanger (44). In the outdoor heat exchanger (44), the refrigerant
dissipates heat to the outdoor air and condenses. The refrigerant
condensed in the outdoor heat exchanger (44) flows sequently
through the first liquid pipe (58), then through the receiver (45),
and then through the second liquid pipe (59), and is admitted to
the liquid side interunit piping (31). The refrigerant admitted to
the liquid side interunit piping (31) diverges into three branches,
namely, the first liquid branch pipe (31a), the second liquid
branch pipe (31b), and the third liquid branch pipe (31c).
[0081] The refrigerant admitted to the first liquid branch pipe
(31a) is pressure reduced during its passage through the indoor
expansion valve (72), and then flows through the indoor heat
exchanger (71). In the indoor heat exchanger (71), the refrigerant
absorbs heat from the indoor air and evaporates. As a result,
indoor space cooling is provided. The refrigerant evaporated in the
indoor heat exchanger (71) flows sequently through the first gas
side interunit piping (32), then through the first four-way
selector valve (47), then through the second four-way selector
valve (48), and then through the third intake pipe (53), and is
drawn into the third compressor (43).
[0082] The refrigerant admitted to the second liquid branch pipe
(31b) is pressure reduced during its passage through the
cold-storage expansion valve (82), and then flows through the
cold-storage heat exchanger (81). In the cold-storage heat
exchanger (81), the refrigerant absorbs heat from the storage
compartment air and evaporates. As a result, the storage
compartment of the cold-storage showcase (13) is refrigerated. In
the cold-storage showcase (13), the storage compartment temperature
is maintained at, for example, 5 degrees Centigrade. The
refrigerant evaporated in the cold-storage heat exchanger (81)
flows into the first gas branch pipe (33a).
[0083] The refrigerant admitted to the third liquid branch pipe
(31c) is pressure reduced during its passage through the
freeze-storage expansion valve (92), and then flows through the
freeze-storage heat exchanger (91). In the freeze-storage heat
exchanger (91), the refrigerant absorbs heat from the storage
compartment air and evaporates. As a result, the storage
compartment of the freeze-storage showcase (14) is refrigerated. In
the freeze-storage showcase (14), the storage compartment
temperature is maintained at, for example, minus 10 degrees
Centigrade. The refrigerant evaporated in the freeze-storage heat
exchanger (91) is compressed in the booster compressor (94), and
then flows into the second gas branch pipe (33b).
[0084] The joined flow of refrigerant in the second gas side
interunit piping (33) diverges again into the first and second
intake pipes (51, 52), the refrigerant diverged into the former of
which is drawn into the first compressor (41) and the refrigerant
diverged into the latter of which is drawn into the second
compressor (42).
Space Heating Operation
[0085] Referring now to FIG. 3, a typical space heating operation
of the refrigeration system (10) will be described below.
[0086] In the space beating operation of this example, the first
four-way selector valve (47) and the second four-way selector valve
(48) are placed in the second state, while the third four-way
selector valve (49) is placed in the first state. In addition, the
outdoor expansion valve (46) and the flow control valve (63) are
fully closed, while the first and second solenoid valves (SV-1,
SV-2) are opened. Furthermore, the indoor expansion valve (72), the
cold-storage expansion valve (82), and the freeze-storage expansion
valve (92) are properly adjusted in their degree of opening. In
addition, the fans (50, 73, 83, 93), the first and second
compressors (41, 42), and the booster compressor (94) are all
placed in operation.
[0087] The flow of refrigerant compressed in the first compressor
(41) and the flow of refrigerant compressed in the second
compressor (42) join together in the delivery piping (57) and the
joined flow of refrigerant again diverges in two refrigerant flows.
One refrigerant flow passes through the second four-way selector
valve (48) and flows through the outdoor heat exchanger (44) where
it condenses. Thereafter, the condensed refrigerant flows, through
the first liquid pipe (58), then through the receiver (45), and
then through the second liquid pipe (59) in that order, into the
liquid side interunit piping (31). Meanwhile, the other refrigerant
flow passes through the first four-way selector valve (47) and then
flows through the indoor heat exchanger (71). In the indoor heat
exchanger (71), the refrigerant dissipates heat to the indoor air
and condenses. As a result, indoor space heating is provided. The
refrigerant condensed in the indoor heat exchanger (71) is pressure
reduced during its passage through the indoor expansion valve (72),
and then flows into the first liquid branch pipe (31a).
[0088] The joined flow of refrigerant in the liquid side interunit
piping (31) again diverges in two branches, namely the second
liquid branch pipe (31b) and the third liquid branch pipe (31c).
The refrigerant admitted to the second liquid branch pipe (31b) is
used to provide refrigeration of the storage compartment of the
cold-storage showcase (13), as in the foregoing space cooling
operation. On the other hand, the refrigerant admitted to the third
liquid branch pipe (31c) is used to provide refrigeration of the
storage compartment of the freeze-storage showcase (14), as in the
foregoing space cooling operation. The flows of refrigerant used to
provide refrigeration of the showcases (13, 14) join together in
the second gas side interunit piping (33). The joined flow of
refrigerant is drawn into the first and second compressors (41,
42).
Air Conditioning Units Thermo-Off Operation in Space Heating
Operation
[0089] During the foregoing space heating operation, the heating
operation by the indoor heat exchanger (71) may no longer be
required in some cases, for example, when the room temperature
reaches a user preset temperature. Therefore, in the refrigeration
system (10), there is carried out a first control operation
(thermo-off operation) to temporarily place the indoor heat
exchanger (71) in the out-of-operation state if a given condition
holds in the foregoing space heating operation.
[0090] More specifically, in the thermo-off operation of the indoor
heat exchanger (71) in the space heating operation, the
degree-of-opening control means (101) of the controller (100)
provides control of the degree of opening of the indoor expansion
valve (72) so that the indoor expansion valve (72) is fully closed.
As a result, most of the refrigerant delivered out from both the
first compressor (41) and the second compressor (42) is fed towards
the outdoor heat exchanger (44), as shown in FIG. 5. The
refrigerant after condensation in the outdoor heat exchanger (44)
is fed, through the same distribution route as in the aforesaid
space heating operation, to each showcase (13, 14) where it is used
to provide refrigeration of the storage compartment.
[0091] On the other hand, in the air conditioning unit (12), the
indoor expansion valve (72) enters the fully closed state and no
refrigerant will flow through the indoor heat exchanger (71).
Consequently, in the indoor heat exchanger (71), there is no active
exchange of heat between the refrigerant and the indoor air and, as
a result, the indoor heat exchanger (71) is substantially placed in
the out-of-operation state (thermo-off state). Thereafter, if a
given condition holds (for example, if the room temperature falls
lower than a preset temperature level by more than a predetermined
value), this places the indoor heat exchanger (71) in the
thermo-off state and the foregoing space heating operation
resumes.
Degree-of-Opening Control Operation after Thermo-Off Operation
[0092] Incidentally, in the thermo-off operation of the indoor heat
exchanger (71) in the space heating operation, the indoor expansion
valve (72) enters the fully closed state as described above.
However, even on this occasion, the gas side of the indoor heat
exchanger (71) still remains in fluid communication with the
refrigerant circulation path. Therefore, after the thermo-off
operation, refrigerant flows into the indoor heat exchanger (71)
and gradually condenses to liquid form and this liquid refrigerant
after condensation will accumulate in gradual degrees within the
indoor heat exchanger (71). That is, in the indoor heat exchanger
(71) in the thermo-off state, there is the possibility that the
so-called "refrigerant's falling-asleep" may occur. If the
accumulated amount of refrigerant within the indoor heat exchanger
(71) increases as described above, the supply of refrigerant to
each showcase (13, 14) decreases accordingly, thereby producing the
problem that the cold-storage heat exchanger (81) and the
freeze-storage heat exchanger (91) deteriorate in their
refrigeration capacity. To cope with this problem, the
degree-of-opening control means (101) of the present embodiment
first provides control so that the indoor expansion valve (72) is
placed in the fully closed state when thermo-offing the air
conditioning unit (12) and, then, a degree-of-opening control
operation (i.e., the second control operation) is performed to
properly adjust the degree of opening of the indoor expansion valve
(72), whereby the elimination of "refrigerant's falling-asleep"
within the indoor heat exchanger (71) can be accomplished.
[0093] In the degree-of-opening control operation, in Step S1, a
determination is made as to whether or not the accumulated amount
of refrigerant within the indoor heat exchanger (71) is great. More
specifically, in Step S1, the pressure difference, (Pc-Th1),
between Pc (the saturated temperature corresponding to the high
pressure found from the values detected by the first delivery
temperature sensor (118) and the first delivery pressure sensor
(119)) and Th1 (the refrigerant temperature detected by the first
refrigerant temperature sensor (123)), is calculated. To sum up, in
Step S1, the degree of refrigerant subcooling, (Pc-Th1), in the
vicinity of the inlet of the indoor heat exchanger (71) is
calculated.
[0094] Here, if the inside of the indoor heat exchanger (71) is
filled with liquid refrigerant, then refrigerant on the inlet side
of the indoor heat exchanger (71) is also in the subcooling state,
and the degree of subcooling, (Pc-Th1), of this refrigerant, too,
increases. In other words, the degree of subcooling, (Pc-Th1), of
such refrigerant serves as an index indicative of the amount of
refrigerant within the indoor heat exchanger (71). Accordingly, if
the degree of subcooling, (Pc-Th1), exceeds T1 degrees Centigrade
(for example, 2 degrees Centigrade), then Step S1 makes a
determination that the accumulated amount of refrigerant within the
indoor heat exchanger (71) is great, and the control procedure
moves to Step S2. In Step S2, the current degree of opening of the
indoor expansion valve (72) is increased by an amount corresponding
to a predetermined number of pulses (for example, 352 pulses). As a
result, the refrigerant accumulated within the indoor heat
exchanger (71) is passed through the indoor expansion valve (72),
flows through the first liquid branch pipe (31a), and is fed into
each showcase (13, 14).
[0095] On the other hand, if the refrigerant accumulated within the
indoor heat exchanger (71) is expelled outside as described above,
the degree of subcooling, (Pc-Th1), will gradually decrease. And,
if, in Step S1, the degree of subcooling, (Pc-Th1), of the
refrigerant falls below T1 degrees Centigrade, then the control
procedure moves from Step S1 to Step S3. In Step S3, it makes a
determination as to whether or not the elimination of
"refrigerant's falling-asleep" within the indoor heat exchanger
(71) is accomplished. More specifically, if the degree of
refrigerant subcooling, (Pc-Th1), on the inflow side of the indoor
heat exchanger (71) continues to fall below T1 degrees Centigrade
for longer than t1 minutes (for example, 3 minutes), then Step S3
makes a determination that very little refrigerant has accumulated
within the indoor heat exchanger (71), and the control procedure
moves to Step S4. As a result, the indoor expansion valve (72)
enters the fully closed state.
[0096] In addition, in Step S3, the temperature difference,
(Pc-Th2), between PC (the saturated temperature corresponding to
the high pressure and Th2 (the refrigerant temperature, detected by
the second refrigerant temperature sensor (124)) is calculated.
That is, in Step S3, the degree of refrigerant subcooling,
(Pc-Th2), immediately before the outlet of the indoor heat
exchanger (71) is also calculated. And if the degree of subcooling,
(Pc-Th2), continues to fall below T2 degrees Centigrade (for
example, 5 degrees Centigrade) for longer than t2 minutes (for
example, 2 minutes), this makes a determination that very little
liquid refrigerant has accumulated within the indoor heat exchanger
(71), and the control procedure moves to Step S4. As a result, the
indoor expansion valve (72) enters the fully closed state. On the
other hand, if neither one of the aforesaid two conditions for Step
S3 holds, then the degree of opening of the indoor expansion valve
(72) is maintained at the current degree of opening.
[0097] Incidentally, there is the possibility that, when detecting
the amount of refrigerant within the indoor heat exchanger (71)
with the aid of the degree of refrigerant subcooling in Step S1 or
Step S3, it may not be detected accurately. More specifically, for
example, if the indoor fan (73) is stopped upon the start-up of the
thermo-off operation, the ambient temperature of the indoor heat
exchanger (71) becomes relatively high. On the other hand, in such
a condition, it is highly possible that, due to the influence of
the ambient temperature of the indoor heat exchanger (71), the
temperatures detected by the first refrigerant temperature sensor
(123) and the second refrigerant temperature sensor (124), too,
will increase above the actual refrigerant temperature. This may
result in the possibility that, in Step S1 or Step S3, the indoor
expansion valve (72) will remain in the fully closed state because
the value of the degree of refrigerant subcooling becomes small
although the accumulated amount of refrigerant within the indoor
heat exchanger (71) is great.
[0098] To cope with the above, if, in the degree-of-opening control
operation, Step S5 makes a determination that the indoor expansion
valve (72) continues to remain in the fully closed state for longer
than t3 minutes (for example, 20 minutes), then the control
procedure moves to Step S6 on the assumption that there is the
possibility that the amount of refrigerant within the indoor heat
exchanger (71) may not have been detected accurately. In Step S6,
the degree of opening of the indoor expansion valve (72) is opened
at a predetermined degree or opening (for example, 352 pulses). As
a result, if there is an accumulation of refrigerant within the
indoor heat exchanger (71), the refrigerant accumulated will be
expelled promptly to outside the indoor heat exchanger (71).
[0099] In addition, if refrigerant is made to flow and pass within
the indoor heat exchanger (71) as described above, this facilitates
the accurate detection of the amount of refrigerant within the
indoor heat exchanger (71) when making a determination in Step S1
or Step S3. That is, after the completion of Step S6, the
continuous supply of refrigerant to the indoor heat exchanger (71)
is made. As a result, the refrigerant flowing in the indoor heat
exchanger (71) is less subject to the influence of the ambient
temperature. Consequently, it is avoided that the value of the
degree of refrigerant subcooling will become small due to the
influence of the ambient temperature. Hence, when making a
determination in the following steps (Steps S1, S3), it becomes
possible to control the degree of opening of the indoor expansion
valve (72) by accurate detection of the amount of refrigerant
within the indoor heat exchanger (71).
[0100] As described above, in the degree-of-opening control
operation shown FIG. 5, each of Steps S1-S6 is repeatedly carried
out so that the degree of opening of the indoor expansion valve
(72) can be properly adjusted depending on the accumulated amount
of refrigerant within the indoor heat exchanger (71) in the
thermo-off state. As a result, the elimination of "refrigerant's
falling-asleep" within the indoor heat exchanger (71) is
accomplished, whereby it is avoided that the cold-storage heat
exchanger (81) and the freeze-storage heat exchanger (91) will
deteriorate in their refrigeration capacity.
Operation Selecting Control after the Thermo-Off Operation
[0101] On the other hand, there is the possibility that, even after
the execution of the degree-of-opening control operation after the
thermo-off operation of the indoor heat exchanger (71), the
elimination of "refrigerant's falling-asleep" within the indoor
heat exchanger (71) will still remain unaccomplished. More
specifically, in the case where the head difference of the
interunit piping (the first gas side interunit piping (32))
extending from the outdoor unit (11) to the air conditioning unit
(12) is great because the air conditioning unit (12) is installed
relatively higher than the outdoor unit (11) of the refrigeration
system (10), there is the possibility that the refrigerant
accumulated within the indoor heat exchanger (71) will not be
sufficiently expelled outside because the refrigerant delivered out
from each compressor (41, 42) is supplied only to the outdoor heat
exchanger (44) even when the degree of opening of the indoor
expansion valve (72) is placed in the fully opened state (for
example, 2000 pulses) by the degree-of-opening control
operation.
[0102] To cope with the above, in the refrigeration system (10) of
the present embodiment, in the case where, after the indoor heat
exchanger (71) is placed in the thermo-off state in the space
heating operation, the elimination of "refrigerant's
falling-asleep" within the indoor heat exchanger (71) still remains
unaccomplished even after the execution of the degree-of-opening
control operation, the operation control means (102) of the
controller (100) provides the following control.
[0103] As shown in FIG. 6, in the first place, Step S11 makes a
determination as to whether or not the elimination of
"refrigerant's falling-asleep" within the indoor heat exchanger
(71) still remains unaccomplished. More specifically, if the degree
of refrigerant subcooling, (Pc-Th1), on the inlet side of the
indoor heat exchanger (71) continues to remain greater than T1
degrees Centigrade for longer than t4 minutes (for example 20
minutes), then Step S11 makes a determination that the elimination
of "refrigerant's falling-asleep" within the indoor heat exchanger
(71) has not yet been accomplished, and the control procedure moves
to Step S12. As a result, in the refrigeration system (10), the
following heat recovery operation is carried out.
[0104] In the heat recovery operation, the first four-way selector
valve (47) is placed in the second state and the second and third
four-way selector valves (48, 49) are placed in the first state. In
addition, the outdoor expansion valve (46) and the flow control
valve (63) are fully closed, while the first and second solenoid
valves (SV-1, SV-2) are opened. Furthermore, the indoor expansion
valve (72), the cold-storage expansion valve (82), and the
freeze-storage expansion valve (92)) are properly adjusted in their
degree of opening. In addition, the fans (50, 73, 83, 93), the
first and second compressors (41, 42), and the booster compressor
(94) are all placed in operation.
[0105] The flows of refrigerant compressed respectively in the
first and second compressors (41, 42) join together in the delivery
piping (57). The joined flow of refrigerant passes through the
first four-way selector valve (47) and then flows through the
indoor heat exchanger (71). In the indoor heat exchanger (71), the
refrigerant accumulated therein is forced out by the high pressure
refrigerant and expelled outside the indoor heat exchanger (71). In
addition, since the refrigerant dissipates heat to the indoor air
and condenses in the indoor heat exchanger (71), the heating
operation is temporarily carried out in the indoor heat exchanger
(71). The refrigerant leaving the indoor heat exchanger (71) is
pressure reduced during its passage through the indoor expansion
valve (72) and then admitted to the first liquid branch pipe (31a).
The refrigerant admitted to the first liquid branch pipe (31a)
diverges into two branches, namely the second liquid branch pipe
(31b) and the third liquid branch pipe (31c).
[0106] The refrigerant admitted to the second liquid branch pipe
(31b) is used to provide refrigeration of the storage compartment
of the cold-storage showcase (13). In addition, the refrigerant
admitted to the third liquid branch pipe (31c) is used to provide
refrigeration of the storage compartment of the freeze-storage
showcase (14). The flows of refrigerant used for the refrigeration
of the showcases (13, 14) join together in the second gas side
interunit piping (33). Thereafter, the joined flow of refrigerant
is drawn into the first and second compressors (41, 42).
[0107] As described above, the heat recovery operation differs from
the aforesaid space heating operation in that the refrigerant
delivered from the first and second compressors (41, 42) is
supplied only towards the air conditioning unit (12). Consequently,
even in the installation situation where the head difference
between the outdoor unit (11) and the air conditioning unit (12) is
great, it is ensured that the supply of high pressure refrigerant
to the air conditioning unit (12) is provided without fail. As a
result, the refrigerant accumulated within the indoor heat
exchanger (71) is expelled outside without fail and is used to
provide refrigeration of each showcase (13, 14).
[0108] On the other hand, during the heat recovery operation as
described above, Step S13 (FIG. 6) makes a determination as to
whether or not the elimination of "refrigerant's falling-asleep"
within the indoor heat exchanger (71) is accomplished. More
specifically, if the degree of refrigerant subcooling within the
indoor heat exchanger (71), (Pc-Th2), continues to remain less than
T2 degrees Centigrade for longer than t5 minutes (for example, 2
minutes), Step S13 makes a determination that the elimination of
"refrigerant's falling-asleep" is accomplished, and the control
procedure moves to Step S14. As a result, in Step S14, the heat
recovery operation is brought to a stop and the indoor heat
exchanger (71) again enters the thermo-off state. In addition, also
when the heat recovery operation is continuously carried out for
longer than t6 minutes (for example, 3 minutes), Step S14 makes a
determination that the elimination of "refrigerant's
falling-asleep" is accomplished without fail, and the control
procedure moves to Step S14.
Advantageous Effects of the Embodiment
[0109] The foregoing embodiment has the following advantageous
effects.
[0110] In the foregoing embodiment, after placing the indoor heat
exchanger (71) in the thermo-off state in the space heating
operation, the degree-of-opening control operation, in which the
degree of opening of the indoor expansion valve (72) is adjusted
based on the index (the degree of refrigerant subcooling)
indicative of the accumulated amount of refrigerant within the
indoor heat exchanger (71), is carried out. More specifically, in
the degree-of-opening control operation, as the accumulated amount
of refrigerant within the indoor heat exchanger (71) increases, the
degree of opening of the indoor expansion valve (72) is increased.
Consequently, in accordance with the foregoing embodiment, the
refrigerant accumulated within the indoor heat exchanger (71) is
properly expelled outside for forwarding to the cold-storage
showcase (13) and to the freeze-storage showcase (14). Accordingly,
it is ensured that the elimination of "refrigerant's
falling-asleep" within the indoor heat exchanger (71) can be
accomplished without fail, whereby it becomes possible to prevent
the deterioration of refrigeration capacity in the storage
compartment of each showcase (13, 14).
[0111] In addition, in the degree-of-opening control operation, the
degree of opening of the expansion valve (72) is reduced if the
accumulated amount of refrigerant within the indoor heat exchanger
(71) is small. Consequently, in accordance with the aforesaid
embodiment, it can be avoided that the excess supply of refrigerant
is provided to the indoor heat exchanger (71) despite the fact that
the elimination of "refrigerant's falling-asleep" within the indoor
heat exchanger (71) has already been accomplished, thereby making
it possible that the supply of refrigerant to be provided to each
showcase (13, 14) is satisfactorily secured. Accordingly, it
becomes possible to more effectively prevent the capacity of
refrigeration of the storage compartment of each showcase (13, 14)
from deterioration.
[0112] In addition, in the degree-of-opening control operation of
the foregoing embodiment, the accumulated amount of refrigerant
within the indoor heat exchanger (71) is detected with the aid of
the degree of refrigerant subcooling on the inlet side of or within
the indoor heat exchanger (71). Consequently, in accordance with
the foregoing embodiment, it is possible to relatively easily
observe the occurrence of the "refrigerant's falling-asleep" within
the indoor heat exchanger (71).
[0113] Furthermore, in the degree-of-opening control operation of
the foregoing embodiment, the indoor expansion valve (72) is opened
if the indoor expansion valve (72) continues to remain in the fully
closed state for longer than a predetermined length of time, in
view of the fact that the degree of refrigerant subcooling
decreases due to the influence of the ambient temperature of the
indoor heat exchanger (71). Consequently, in accordance with the
foregoing embodiment, it can be avoided that the indoor expansion
valve (72) enters the state of remaining closed despite that fact
that the "refrigerant's falling-asleep" is in fact occurring in the
indoor heat exchanger (71). This makes it sure that the elimination
of "refrigerant's falling-asleep" within the indoor heat exchanger
(71) is accomplished without fail.
[0114] In addition, by the arrangement that allows the flow of
refrigerant within the indoor heat exchanger (71) as described
above, the degree of refrigerant subcooling is less subject to the
influence of the ambient temperature of the indoor heat exchanger
(71) in the subsequent degree-of-opening control operation, whereby
the amount of refrigerant within the indoor heat exchanger (71) can
be detected with accuracy. Consequently, in accordance with the
present embodiment, it is possible to properly control the degree
of opening of the expansion valve (72) depending on the accumulated
amount of refrigerant within the indoor heat exchanger (71). This
therefore makes it sure that the elimination of "refrigerant's
falling-asleep" within the indoor heat exchanger (71) can be
accomplished without fail and, in addition, the sufficient supply
of refrigerant to each showcase (13, 14) can be secured.
[0115] Furthermore, in the foregoing embodiment, the heat recovery
operation is carried out in the refrigerant circuit (20) if the
elimination of "refrigerant's falling-asleep" within the indoor
heat exchanger (71) still remains unaccomplished even when the
degree-of-opening control operation is performed by the
degree-of-opening control means (101) after the execution of the
thermo-off operation of the indoor heat exchanger (71). In the heat
recovery operation, the total amount of refrigerant delivered out
from each compressor (41, 42) is fed towards the indoor heat
exchanger (71). Accordingly, in accordance with the foregoing
embodiment, even in the case where the head difference of the
interunit piping extending from the outdoor unit (11) to the air
conditioning unit (12) is relatively great, it is ensured that the
refrigerant delivered out from each compressor (41, 42) can be fed
into the indoor heat exchanger (71), thereby making it sure that
the elimination of the occurrence of "refrigerant's falling-asleep"
within the indoor heat exchanger (71) can be accomplished.
Other Embodiments
[0116] The foregoing embodiment may be configured as follows.
[0117] In the foregoing embodiment, the number of air conditioning
units (12) connected to the outdoor unit (11) is one.
Alternatively, a plurality of air conditioning units of such a type
may be connected to the outdoor unit (11). Also in this case, the
elimination of "refrigerant's falling-asleep" in each indoor heat
exchanger can be accomplished by the execution of the foregoing
degree-of-opening control operation after the thermo-offing of the
indoor heat exchanger of each air conditioning unit.
[0118] In addition, in the foregoing embodiment, in the space
heating operation, the fully closing of the indoor expansion valve
(72) is carried out as the thermo-off operation of the indoor heat
exchanger (71). However, as the thermo-off operation, the degree of
opening of the indoor expansion valve (72) may be reduced to a very
small degree of opening. Also in this case, after that time, the
accumulation of refrigerant will gradually proceed within the
indoor heat exchanger (71). To cope with this, the foregoing
degree-of-opening control operation is carried out to eliminate the
"refrigerant's falling-asleep".
[0119] Furthermore, in the foregoing embodiment, the accumulated
amount of refrigerant within the indoor heat exchanger (71) in the
thermo-off state is found from the degree of refrigerant subcooling
on the inflow side of or within the indoor heat exchanger (71).
However, the accumulated amount of refrigerant within the indoor
heat exchanger (71) may be found by other than the above
method.
[0120] It should be noted that the above-described embodiments are
merely preferable exemplifications in nature and are no way
intended to limit the scope of the present invention, its
application, or its application range.
INDUSTRIAL APPLICABILITY
[0121] As has been described above, the present invention finds its
utility in the prevention of "refrigerant's falling-asleep" in a
heating heat exchanger placed in the out-of-operation state in a
refrigeration system having a plurality of utilization units.
* * * * *