Field of the Invention
[0001] The present invention relates to a refrigeration apparatus, an environment forming
apparatus, and a refrigeration method.
Background Art
[0002] Conventionally, as disclosed in
JP S54-31657 A, a refrigeration apparatus including a refrigeration circuit provided with a supercooler
is known. In this type of refrigeration apparatus, in a main refrigeration circuit
including a compressor, a condenser, an expansion valve, and an evaporator, a supercooler
is provided between the condenser and the expansion valve. The supercooler is connected
to a supercooling refrigeration circuit provided with another compressor, another
condenser, and another expansion valve. In the supercooler, a refrigerant in the main
refrigeration circuit is supercooled by a refrigerant in the supercooling refrigeration
circuit, so that the refrigeration capacity in the main refrigeration circuit can
be increased.
[0003] When the supercooler is configured to exchange heat between the refrigerant in the
supercooling refrigeration circuit and the refrigerant in the main refrigeration circuit,
as compared with a case where only one refrigeration circuit exhibits an equivalent
refrigeration capacity, a compressor having a smaller compressor capacity as compared
with the compressor in the one refrigeration circuit can exhibit the equivalent refrigeration
capacity. Thus, energy saving is achieved by providing the supercooler, but further
energy saving is required.
Summary of the Invention
[0004] An object of the present invention is not only to achieve energy saving by using
a supercooling heat exchanger but also to achieve further energy saving.
[0005] A refrigeration apparatus according to one aspect of the present invention includes
a main refrigeration circuit in which a first refrigerant is sealed and which is provided
with a first compressor, a first condenser, a supercooling heat exchanger, a first
expansion mechanism, and a first evaporator, a supercooling refrigeration circuit
in which a second refrigerant is sealed and which is provided with a second compressor,
a second condenser, and a second expansion mechanism and which is connected to the
supercooling heat exchanger, and a controller configured to execute superheating degree
setting control and superheating degree control. The supercooling heat exchanger is
configured to supercool the first refrigerant in the main refrigeration circuit by
evaporation of the second refrigerant in the supercooling refrigeration circuit. The
controller is configured to set, in the superheating degree setting control, a target
value of a degree of superheat of the second refrigerant on an outlet side of the
supercooling heat exchanger to a first value when a refrigeration request degree is
a first request value, and set the target value of the degree of superheat to a second
value larger than the first value when the refrigeration request degree is a second
request value smaller than the first request value. The controller is configured to
control, in the superheating degree control, the second expansion mechanism based
on the target value of the degree of superheat set by the superheating degree setting
control.
[0006] An environment forming apparatus according to one aspect of the present invention
includes an environment chamber and the refrigeration apparatus for cooling an inside
of the environment chamber.
[0007] A refrigeration method according to one aspect of the present invention is a refrigeration
method using a refrigeration apparatus, the refrigeration apparatus including a main
refrigeration circuit in which a first refrigerant is sealed and which is provided
with a first compressor, a first condenser, a supercooling heat exchanger, a first
expansion mechanism, and a first evaporator, and a supercooling refrigeration circuit
in which a second refrigerant is sealed and which is provided with a second compressor,
a second condenser, and a second expansion mechanism and which is connected to the
supercooling heat exchanger, the refrigeration method comprising: receiving a refrigeration
request degree in the refrigeration apparatus; setting a target value of a degree
of superheat of the second refrigerant on an outlet side of the supercooling heat
exchanger to a first value when the received refrigeration request degree is a first
request value; setting a target value of the degree of superheat to a second value
larger than the first value when the received refrigeration request degree is a second
request value smaller than the first request value; controlling the second expansion
mechanism based on the set target value of the degree of superheat; and supercooling
the first refrigerant in the main refrigeration circuit by evaporation of the second
refrigerant in the supercooling heat exchanger into which the second refrigerant having
a flow rate adjusted by the second expansion mechanism flows.
Brief Description of the Drawings
[0008]
Fig. 1 is a diagram schematically illustrating a configuration of a refrigeration
apparatus according to a first embodiment.
Fig. 2 is a diagram schematically illustrating a control device including a controller
of the refrigeration apparatus.
Fig. 3 is a diagram for describing a relationship between a refrigeration request
degree and a target superheating degree.
Fig. 4 is a diagram for describing a relationship between the refrigeration request
degree and the target superheating degree.
Fig. 5 is a diagram for describing a relationship between the refrigeration request
degree and the target superheating degree.
Fig. 6 is a diagram for describing an operation of the refrigeration apparatus.
Fig. 7 is a diagram schematically illustrating a configuration of a refrigeration
apparatus according to a second embodiment.
Fig. 8 is a diagram schematically illustrating a configuration of a refrigeration
apparatus according to a modification of the second embodiment.
Fig. 9 is a diagram schematically illustrating a configuration of a refrigeration
apparatus according to a third embodiment.
Fig. 10 is a diagram schematically illustrating an environment forming apparatus according
to a fourth embodiment.
Description of Embodiments
[0009] Hereinafter, embodiments of the present invention will be described in detail with
reference to the drawings.
(First Embodiment)
[0010] As illustrated in Fig. 1, a refrigeration apparatus 10 according to a first embodiment
includes a main refrigeration circuit 15 in which a first refrigerant is sealed, and
a supercooling refrigeration circuit 16 in which a second refrigerant is sealed. The
first refrigerant may be, for example, a refrigerant such as R-449A, R-404A, or R-448A.
The second refrigerant may be a refrigerant of the same type as the first refrigerant,
or may be a refrigerant of a type different from the first refrigerant. The second
refrigerant may be, for example, a refrigerant such as R-449A, R-404A, R-448A, R-134a,
or R-513A.
[0011] The main refrigeration circuit 15 is provided with a first compressor 1, a first
condenser 2, a supercooling heat exchanger 14, a first expansion mechanism 3, and
a first evaporator 4 in this order. When the first compressor 1 operates, the first
refrigerant circulates in the main refrigeration circuit 15, thereby performing a
vapor compression refrigeration cycle. The refrigeration apparatus 10 may be used
to cool air inside a freezer or a refrigerator, or may be used to generate cooling
water by a chiller. Alternatively, the refrigeration apparatus 10 may be used in an
environment forming apparatus such as an environment testing apparatus for providing
a temperature environment of a predetermined temperature. Note that, in the present
embodiment, it is assumed that the refrigeration apparatus 10 is used in a freezer.
[0012] The first compressor 1 is responsible for a compression process of a refrigeration
cycle, and is configured to suction and compress the first refrigerant. The first
compressor 1 includes, for example, a scroll type compression mechanism, a screw type
compression mechanism, or the like, and is configured to drive the compression mechanism
by a motor at a constant rotation speed. Note that the first compressor 1 may be configured
so that the rotation speed of the motor can be adjusted by an inverter. In addition,
the first compressor 1 may include one unit compressor, but alternatively may include
two or more unit compressors connected in parallel and having different capacities.
[0013] The first condenser 2 is responsible for a condensation process of the refrigeration
cycle, and is configured to exchange heat of the first refrigerant discharged from
the first compressor 1 with a cooling medium such as air, water, or a refrigerant
to condense the first refrigerant.
[0014] The first expansion mechanism 3 is responsible for an expansion process of the refrigeration
cycle, and is configured to expand the first refrigerant in a liquid state condensed
in the first condenser 2. Note that, when the supercooling heat exchanger 14 is functioning,
the first refrigerant having a higher supercooling degree in the supercooling heat
exchanger 14 flows into the first expansion mechanism 3.
[0015] The first expansion mechanism 3 includes, for example, an electronic expansion valve.
Thus, by adjusting the valve opening degree of the first expansion mechanism 3, it
is possible to arbitrarily change the flow rate of the first refrigerant flowing through
the supercooling heat exchanger 14 and the first evaporator 4 in the main refrigeration
circuit 15.
[0016] The first evaporator 4 is responsible for an evaporation process of the refrigeration
cycle, and is configured to exchange heat between the first refrigerant in a liquid
state decompressed in the first expansion mechanism 3 and air to evaporate the first
refrigerant. The first evaporator 4 cools air (object to be cooled) supplied to the
inside of the freezer (the room to be cooled). Note that, when the refrigeration apparatus
10 is provided in a chiller that generates cooling water, the first evaporator 4 evaporates
the first refrigerant to cool the cooling water (object to be cooled).
[0017] The supercooling refrigeration circuit 16 is provided with a second compressor 11,
a second condenser 12, a second expansion mechanism 13, and a supercooling heat exchanger
14 in this order. When the second compressor 11 operates, the second refrigerant circulates
in the supercooling refrigeration circuit 16, thereby performing a vapor compression
refrigeration cycle.
[0018] The second compressor 11 is responsible for a compression process of a refrigeration
cycle, and is configured to suction and compress the second refrigerant. The second
compressor 11 includes, for example, a scroll type compression mechanism, a screw
type compression mechanism, or the like, and is configured to drive the compression
mechanism by a motor at a constant rotation speed. Note that the second compressor
11 may be configured so that the rotation speed of the motor can be adjusted by an
inverter. In addition, the second compressor 11 may include one unit compressor, or
alternatively may include two or more unit compressors connected in parallel and having
different capacities.
[0019] The capacity of the second compressor 11 is smaller than the capacity of the first
compressor 1. Note that the relationship between the capacities of the first compressor
1 and the second compressor 11 is not limited thereto.
[0020] The second condenser 12 is responsible for a condensation process of the refrigeration
cycle, and is configured to exchange heat of the second refrigerant discharged from
the second compressor 11 with a cooling medium such as air, water, or a refrigerant
to condense the second refrigerant.
[0021] The second expansion mechanism 13 is responsible for an expansion process of the
refrigeration cycle, and is configured to expand the second refrigerant in a liquid
state condensed in the second condenser 12. The second expansion mechanism 13 includes,
for example, an electronic expansion valve. Thus, by adjusting the valve opening degree
of the second expansion mechanism 13, it is possible to arbitrarily change the flow
rate of the second refrigerant flowing through the supercooling heat exchanger 14
in the supercooling refrigeration circuit 16.
[0022] The supercooling heat exchanger 14 is configured to cause heat exchange between the
first refrigerant flowing through the main refrigeration circuit 15 and the second
refrigerant flowing through the supercooling refrigeration circuit 16. The second
refrigerant decompressed by the second expansion mechanism 13 and adjusted in flow
rate flows into the supercooling heat exchanger 14, and the first refrigerant in a
liquid state flowing out of the first condenser 2 flows into the supercooling heat
exchanger. Then, in the supercooling heat exchanger 14, the second refrigerant evaporates
to supercool the first refrigerant in a liquid state.
[0023] The supercooling refrigeration circuit 16 is provided with an inflow side temperature
detector 21 and an outflow side temperature detector 22, the inflow side temperature
detector 21 being for detecting the temperature of the second refrigerant flowing
into the supercooling heat exchanger 14, and the outflow side temperature detector
22 being for detecting the temperature of the second refrigerant flowing out of the
supercooling heat exchanger 14. The temperature detectors 21 and 22 each output a
signal indicating the detected temperature.
[0024] The signals output from the temperature detectors 21 and 22 are input to the controller
100. The controller 100 includes a microcomputer including a CPU that executes arithmetic
processing, a ROM that stores a processing program, data, and the like, and a RAM
that temporarily stores data, and the like. By executing the processing program stored
in the controller 100, as illustrated in Fig. 2, the controller 100 can function as
a reception unit 101, a superheating degree deriving unit 102, a superheating degree
setting unit 103, a superheating degree control unit 104, a compressor control unit
105, and a refrigeration capacity control unit 106.
[0025] The reception unit 101 is configured to repeatedly receive a refrigeration request
degree at predetermined time intervals, and temporarily store the received refrigeration
request degree. The refrigeration request degree is generated by a generator 120,
and the refrigeration request degree generated by the generator 120 is input to the
reception unit 101. Note that, in Fig. 2, the generator 120 is configured separately
from the controller 100, but the generator 120 of the refrigeration request degree
may be one function of the controller 100.
[0026] For example, the generator 120 repeatedly receives signals from a sensor 121 that
detects the in-freezer temperature (or the temperature of the room to be cooled in
the freezer), an input device 122 for inputting the set value of the in-freezer temperature,
and the like at predetermined time intervals, and calculates the refrigeration request
degree each time. The refrigeration request degree is a dimensionless numerical value
that indicates the refrigeration load in the freezer, and is calculated by, for example,
a difference value between a detection value and a set value of the in-freezer temperature.
Thus, the larger the difference of the detected in-freezer temperature from the set
value of the in-freezer temperature, the larger the refrigeration request degree.
Since the refrigeration request degree can change from moment to moment, the generator
120 outputs the refrigeration request degree every predetermined time.
[0027] The superheating degree deriving unit 102 is configured to derive a difference value
between the temperature detected by the outflow side temperature detector 22 and the
temperature detected by the inflow side temperature detector 21 as the degree of superheat
of the second refrigerant on the outlet side of the supercooling heat exchanger 14.
That is, in the supercooling refrigeration circuit 16, the second refrigerant in a
liquid state decompressed by the second expansion mechanism 13 is saturated or nearly
saturated. Thus, the temperature difference between the temperature of the second
refrigerant in a gaseous state flowing out of the supercooling heat exchanger 14 and
the temperature of the second refrigerant in a liquid state flowing into the supercooling
heat exchanger 14 corresponds to the degree of superheat of the second refrigerant
on the outlet side of the supercooling heat exchanger 14.
[0028] Note that the degree of superheat of the second refrigerant on the outlet side of
the supercooling heat exchanger 14 can also be calculated by other methods. For example,
a temperature detector (or outflow side temperature detector 22) and a pressure detector
may be disposed on the outlet side of the supercooling heat exchanger 14, and the
superheating degree deriving unit 102 may calculate the degree of superheat of the
second refrigerant using a saturated vapor temperature corresponding to the pressure
detected by the pressure detector and the temperature detected by the temperature
detector (or outflow side temperature detector 22). In this case, since the pressure
detected by the pressure detector becomes the suction pressure of the second compressor
11, the saturated vapor temperature corresponding to the suction pressure to the second
compressor 11 can be obtained. The method of calculating the degree of superheat is
not limited to the refrigeration apparatus 10 according to the first embodiment, and
is also applicable to the refrigeration apparatuses 10 according to the second and
third embodiments described later.
[0029] The superheating degree setting unit 103 is configured to set a target superheating
degree, which is a target value of the degree of superheat of the second refrigerant
on the outlet side of the supercooling heat exchanger 14. That is, the controller
100 stores logic for setting the target superheating degree. As illustrated in Fig.
3, the logic is configured to set the target superheating degree to a value in accordance
with the received refrigeration request degree. Specifically, the target superheating
degree is set to a first value when the received refrigeration request degree is equal
to or more than a preset threshold TV, and is set to gradually increase from the first
value as the refrigeration request degree decreases when the received refrigeration
request degree is less than the threshold TV. That is, the controller 100 can execute
superheating degree setting control of setting the target superheating degree to a
second value larger than the first value when the received refrigeration request degree
is a second request value that is a refrigeration request degree smaller than a first
request value while setting the value of the target superheating degree as the first
value when the received refrigeration request degree is the first request value. Further,
in the superheating degree setting control, when the received refrigeration request
degree is less than the threshold TV, the target superheating degree is set to a larger
value as the refrigeration request degree is smaller.
[0030] Fig. 3 illustrates an example in which the manner of changing the target superheating
degree varies depending on whether the refrigeration request degree is equal to or
more than the threshold TV or less than the threshold TV, but it is not limited thereto.
For example, as illustrated in Fig. 4, the target superheating degree may be set to
gradually increase as the refrigeration request degree decreases without providing
the threshold TV. Even in this case, the target superheating degree becomes the minimum
value when the refrigeration request degree is the maximum request value, and the
target superheating degree can take a value higher than the minimum value when the
refrigeration request degree is smaller than the maximum request value. Specifically,
when the refrigeration request degree is the maximum request value, the superheating
degree setting unit 103 sets the target superheating degree of the second refrigerant
to the minimum value, and when the refrigeration request degree is smaller than the
maximum request degree, the target superheating degree can be set to a value larger
than the target superheating degree set when the refrigeration request degree is the
maximum request value. If the target superheating degree is set in this manner, the
threshold TV may or may not be set.
[0031] Here, the maximum request value means a request value when the set value is the minimum
value that can be set and the in-freezer temperature is the highest value that can
be taken in a case where the refrigeration request degree is calculated by, for example,
the difference value between the detection value and the set value of the in-freezer
temperature. That is, the maximum request value is a maximum value of a value obtained
from a conceivable condition as the refrigeration request degree.
[0032] Note that, as illustrated in Fig. 5, in a case where the threshold TV is set in advance,
the target superheating degree may be set so that the target superheating degree gradually
increases as the refrigeration request degree decreases when being equal to or more
than the threshold TV, and on the other hand, the target superheating degree may be
set so that the target superheating degree becomes constant when the refrigeration
request degree being less than the threshold TV. Even in this case, when the refrigeration
request degree is the maximum request value, the target superheating degree becomes
the minimum value, and when the refrigeration request degree is smaller than the maximum
request value, the target superheating degree can take a value higher than the minimum
value.
[0033] The superheating degree control unit 104 is configured to control the second expansion
mechanism 13 so that the degree of superheat of the second refrigerant derived by
the superheating degree deriving unit 102 becomes the target superheating degree set
by the superheating degree setting unit 103. That is, the controller 100 can execute
superheating degree control of controlling the second expansion mechanism 13 based
on the target superheating degree.
[0034] When the opening degree of the second expansion mechanism 13 is reduced, the flow
rate of the second refrigerant flowing through the supercooling refrigeration circuit
16 is reduced. Thus, the second refrigerant is further superheated in the supercooling
heat exchanger 14, and the degree of superheat of the second refrigerant on the outlet
side of the supercooling heat exchanger 14 is further increased. On the other hand,
when the opening degree of the second expansion mechanism 13 is increased, the flow
rate of the second refrigerant flowing through the supercooling refrigeration circuit
16 increases. Thus, the second refrigerant is not superheated so much in the supercooling
heat exchanger 14, and the degree of superheat of the second refrigerant on the outlet
side of the supercooling heat exchanger 14 becomes smaller. Therefore, the superheating
degree control unit 104 controls the second expansion mechanism 13 so that the degree
of superheat of the second refrigerant approaches the target superheating degree.
[0035] The compressor control unit 105 is configured to stop the second compressor 11 after
the target superheating degree is increased to a predetermined maximum value. That
is, the controller 100 can execute compressor control for stopping the second compressor
11 after the superheating degree target value is gradually increased.
[0036] When the target superheating degree is increased to the maximum value, the degree
of supercool of the first refrigerant on the outlet side of the supercooling heat
exchanger 14 decreases accordingly. Therefore, the refrigeration capacity exhibited
by the first evaporator 4 is also reduced. Thus, since the second compressor 11 is
stopped in a state where the degree of supercool is small, even if the second compressor
11 is stopped, occurrence of control disturbance of the temperature in the freezer
can be suppressed. Note that the configuration for stopping the second compressor
11 after the target superheating degree is increased to the maximum value can be omitted.
[0037] The refrigeration capacity control unit 106 is configured to control the first expansion
mechanism 3 so that the flow rate of the first refrigerant passing through the first
expansion mechanism 3 is adjusted in accordance with the refrigeration request degree
received by the reception unit 101. That is, the controller 100 can execute refrigeration
capacity control for controlling the first expansion mechanism 3 based on the refrigeration
request degree.
[0038] Specifically, information in which a target evaporation temperature is assigned to
the received refrigeration request degree is stored, and the refrigeration capacity
control unit 106 controls the first expansion mechanism 3 so as to obtain the target
evaporation temperature obtained from the received refrigeration request degree. That
is, the refrigeration capacity control unit 106 is configured to adjust the flow rate
of the first refrigerant flowing into the first evaporator 4 in accordance with the
refrigeration request degree.
[0039] Note that the control of the first expansion mechanism 3 by the refrigeration capacity
control unit 106 is not limited to control to obtain a target evaporation temperature.
It is sufficient if the flow rate of the first refrigerant flowing into the first
evaporator 4 is adjusted in accordance with the received refrigeration request degree
without setting a target evaporation temperature. In this case, for example, information
in which the opening degree of the first expansion mechanism 3 is assigned to the
refrigeration request degree may be stored, and the opening degree of the first expansion
mechanism 3 may be set according to the refrigeration request degree.
[0040] Here, a refrigeration method using the refrigeration apparatus 10 having the above
configuration will be described with reference to Fig. 6.
[0041] When a target temperature of the in-freezer temperature (or the temperature of the
room to be cooled in the freezer or the temperature in the freezing compartment) is
set and operation of the refrigeration apparatus 10 is started, the controller 100
receives the refrigeration request degree generated by the generator 120 (step ST11),
and receives the temperature detected by the inflow side temperature detector 21 and
the temperature detected by the outflow side temperature detector 22 (step ST12).
The refrigeration capacity control unit 106 of the controller 100 adjusts the opening
degree of the first expansion mechanism 3 based on the received refrigeration request
degree (step ST13). That is, the refrigeration capacity control unit 106 adjusts the
opening degree of the first expansion mechanism 3 based on the refrigeration request
degree so as to obtain the target evaporation temperature. Thus, in the main refrigeration
circuit 15, the flow rate of the first refrigerant according to the refrigeration
request degree is obtained, and thus desired refrigeration capacity is exhibited.
[0042] On the other hand, in the supercooling refrigeration circuit 16, the superheating
degree deriving unit 102 derives a difference value between the temperature detected
by the outflow side temperature detector 22 and the temperature detected by the inflow
side temperature detector 21 as the degree of superheat of the second refrigerant
on the outlet side of the supercooling heat exchanger 14 (step ST14). Furthermore,
the superheating degree setting unit 103 sets the target superheating degree, which
is a target value of the degree of superheat of the second refrigerant on the outlet
side of the supercooling heat exchanger 14, to a value corresponding to the refrigeration
request degree (step ST15). Specifically, the superheating degree setting unit 103
sets the target superheating degree to the first value when the received refrigeration
request degree is equal to or more than the preset threshold TV. On the other hand,
when the received refrigeration request degree is less than the threshold TV, the
superheating degree setting unit 103 sets the target superheating degree so that the
target superheating degree gradually increases from the first value as the refrigeration
request degree decreases.
[0043] Subsequently, the superheating degree control unit 104 controls the second expansion
mechanism 13 so that the degree of superheat of the second refrigerant derived by
the superheating degree deriving unit 102 becomes the target superheating degree set
by the superheating degree setting unit 103 (step ST16). At this time, if the received
refrigeration request degree is equal to or more than the threshold TV, the target
superheating degree is set to the first value, and thus the second expansion mechanism
13 is controlled so that the degree of superheat becomes the first value. At this
time, the target superheating degree is set to the first value regardless of the change
in the refrigeration request degree, but in the main refrigeration circuit 15, the
first expansion mechanism 3 is controlled according to the refrigeration request degree.
That is, in the main refrigeration circuit 15, the flow rate of the first refrigerant
flowing through the first evaporator 4 changes according to the refrigeration request
degree. Thus, the second expansion mechanism 13 is adjusted in accordance with a change
in the flow rate of the first refrigerant. However, since the target superheating
degree is set to a constant value, the control of the second expansion mechanism 13
is not complicated.
[0044] On the other hand, when the received refrigeration request degree gradually decreases
and becomes less than the threshold TV, the target superheating degree is set to a
higher value. Thus, the opening degree of the second expansion mechanism 13 is adjusted
to be smaller than the opening degree when the refrigeration request degree is equal
to or more than the threshold TV. Moreover, in this case, the second expansion mechanism
13 is controlled so that the target superheating degree increases as the refrigeration
request degree decreases. Thus, the opening degree of the second expansion mechanism
13 becomes smaller as the refrigeration request degree becomes smaller. Thus, the
flow rate of the second refrigerant flowing through the supercooling heat exchanger
14 is reduced, so that the degree of supercool of the first refrigerant on the outlet
side of the supercooling heat exchanger 14 is further reduced. Therefore, as compared
with a case where the superheating degree target value is maintained at a constant
value, the degree of supercool of the first refrigerant is smaller, and the refrigeration
capacity exhibited in the first evaporator 4 is reduced. Moreover, power of the first
compressor 1 is also reduced, so that energy consumption in main refrigeration circuit
15 is reduced.
[0045] Furthermore, after the value of the refrigeration request degree decreases and the
target superheating degree increases to the maximum value, the second compressor 11
is stopped (step ST17). Therefore, energy consumption in the supercooling refrigeration
circuit 16 is further reduced. At this time, since the refrigeration capacity exhibited
in the supercooling heat exchanger 14 is reduced, even if the second compressor 11
is stopped, occurrence of control disturbance of the temperature in the freezer is
suppressed.
[0046] Note that the control for stopping the second compressor 11 (step ST17) can be omitted.
In addition, after the target superheating degree is increased to the maximum value
or when the target superheating degree reaches a predetermined ratio (that is, a ratio
at which the second refrigerant hardly flows) to the maximum value, the second expansion
mechanism 13 may be switched from the control based on the target superheating degree
to the control according to the refrigeration request degree. That is, the controller
100 may be capable of executing supercooling degree adjustment control of controlling
the second expansion mechanism 13 based on the refrigeration request degree.
[0047] As described above, in the present embodiment, in the supercooling heat exchanger
14, the second refrigerant in the supercooling refrigeration circuit 16 evaporates
to supercool the first refrigerant in the main refrigeration circuit 15, and thus
the refrigeration capacity exhibited by the main refrigeration circuit 15 increases
accordingly. Therefore, as compared with a case where only one refrigeration circuit
exhibits an equivalent refrigeration capacity, a compressor having a smaller compressor
capacity can exhibit the equivalent refrigeration capacity. Furthermore, when the
value of the refrigeration request degree is the second request value (or when the
value of the refrigeration request degree is smaller than the first request value),
the target value of the degree of superheat of the second refrigerant on the outlet
side of the supercooling heat exchanger 14 is set to the second value (larger than
the first value). Then, the second expansion mechanism 13 is controlled based on the
target value of the degree of superheat of the second refrigerant on the outlet side
of the supercooling heat exchanger 14. Thus, the flow rate of the second refrigerant
circulating in the supercooling refrigeration circuit 16 decreases as compared with
the flow rate based on the target value of the degree of superheat when the refrigeration
request degree is the first request value. Thus, power of the second compressor 11
of the supercooling refrigeration circuit 16 decreases as compared with that in a
case where the target superheating degree is controlled to be constant, so that further
energy saving of the supercooling refrigeration circuit 16 can be achieved when the
refrigeration request degree is relatively small.
[0048] Further, in the present embodiment, since the target superheating degree is set to
the minimum value when the refrigeration request degree is the maximum request value,
the flow rate of the second refrigerant circulating through the supercooling refrigeration
circuit 16 is maximized by controlling the second expansion mechanism 13 to achieve
the target superheating degree. Thus, the degree of supercool of the first refrigerant
on the outlet side of the supercooling heat exchanger 14 in the main refrigeration
circuit 15 also increases. Therefore, a larger refrigeration capacity can be exhibited.
[0049] Further, in the present embodiment, the target superheating degree is set as the
first value when the refrigeration request degree is equal to or more than the preset
threshold TV, and the value of the target superheating degree is gradually increased
from the first value as the refrigeration request degree decreases when the refrigeration
request degree is less than the threshold TV. Thus, when the refrigeration request
degree is equal to or more than the threshold TV, a predetermined refrigeration capacity
can be exhibited, and when the refrigeration request degree is less than the threshold
TV and stable, further energy saving of the supercooling refrigeration circuit 16
can be achieved.
(Second Embodiment)
[0050] As illustrated in Fig. 7, in a second embodiment, a bypass flow path 18 is provided
in the supercooling refrigeration circuit 16. Here, the same components as those of
the first embodiment are denoted by the same reference numerals, and a detailed description
thereof will be omitted.
[0051] The bypass flow path 18 is a flow path for returning the second refrigerant flowing
out of the second condenser 12 to the second compressor 11 without flowing through
the supercooling heat exchanger 14. One end portion of the bypass flow path 18 is
connected to a portion of the supercooling refrigeration circuit 16 between the second
condenser 12 and the second expansion mechanism 13, and the other end portion is connected
to a portion of the supercooling refrigeration circuit 16 between the supercooling
heat exchanger 14 and the second compressor 11.
[0052] The bypass flow path 18 is provided with a bypass expansion mechanism 17 and a bypass
evaporator 5. The bypass evaporator 5 is disposed on the downstream side of the bypass
expansion mechanism 17 in the bypass flow path 18, and exchanges heat between the
second refrigerant decompressed by the bypass expansion mechanism 17 and the air supplied
to the inside of the freezer (the room to be cooled). Note that, when the refrigeration
apparatus 10 is provided in a chiller that generates cooling water, the bypass evaporator
5 evaporates the second refrigerant to cool the cooling water (object to be cooled).
[0053] The bypass expansion mechanism 17 includes, for example, an electronic expansion
valve, and the opening degree thereof is controlled by the controller 100. That is,
the refrigeration capacity control unit 106 is configured to control the first expansion
mechanism 3 and the bypass expansion mechanism 17 in accordance with the refrigeration
request degree.
[0054] The controller 100 can execute, for example, rapid cooling control to cause both
the first evaporator 4 and the bypass evaporator 5 to function in a state where the
supercooling heat exchanger 14 does not function. Further, the controller 100 can
also execute supercooling control to cause only the first evaporator 4 to function
while causing the supercooling heat exchanger 14 to function. In addition, the controller
100 can execute intermediate cooling control in which only the first evaporator 4
functions in a state where the supercooling heat exchanger 14 does not function. Further,
the controller 100 can execute weak cooling control for causing only the bypass evaporator
5 to function. Note that any of the rapid cooling control, the intermediate cooling
control, and the weak cooling control can be omitted. In addition, other control can
be performed.
[0055] In the rapid cooling control, the first expansion mechanism 3 and the bypass expansion
mechanism 17 are controlled to have opening degrees according to the refrigeration
request degree. Thus, the air supplied into the freezer is cooled by both the first
evaporator 4 and the bypass evaporator 5. That is, the refrigeration capacity control
unit 106 controls the first expansion mechanism 3 and the bypass expansion mechanism
17 in accordance with the refrigeration request degree received by the reception unit
101. In this rapid cooling control, the second expansion mechanism 13 is closed to
cause the bypass evaporator 5 to function. The rapid cooling control is executed when
the refrigeration request degree is large and the in-freezer temperature is relatively
high. In the rapid cooling control, compressor power increases, but a large refrigeration
capacity can be exhibited.
[0056] In the supercooling control, the first expansion mechanism 3 and the second expansion
mechanism 13 are controlled to the opening degrees according to the refrigeration
request degree, while the bypass expansion mechanism 17 is closed. That is, in the
supercooling control, the operation using the supercooling heat exchanger 14 is performed
in the main refrigeration circuit 15 without using the bypass evaporator 5. In this
case, in the supercooling control, the same control as the control described in the
first embodiment is executed. In addition, in the supercooling control, the bypass
expansion mechanism 17 may be controlled to open as the opening degree of the first
expansion mechanism 3 decreases. In this case, since the opening degree of the first
expansion mechanism 3 decreases and the opening degree of the bypass expansion mechanism
17 increases as the refrigeration request degree decreases, it is possible to suppress
control disturbance at the time of switching or transition from the supercooling control
to the weak cooling control.
[0057] That is, the refrigeration capacity control unit 106 controls the first expansion
mechanism 3 so that the flow rate of the first refrigerant passing through the first
evaporator 4 is adjusted in accordance with the refrigeration request degree received
by the reception unit 101. Further, the superheating degree control unit 104 also
controls the second expansion mechanism 13 so that the degree of superheat of the
second refrigerant derived by the superheating degree deriving unit 102 becomes the
target superheating degree set by the superheating degree setting unit 103. At this
time, the superheating degree setting unit 103 sets the value of the target superheating
degree when the received refrigeration request degree is the first request value as
the first value, and sets the target superheating degree as the second value larger
than the first value when the received refrigeration request degree is the second
request value that is a refrigeration request degree smaller than the first request
value. Therefore, in the supercooling control, the second expansion mechanism 13 is
controlled while the target superheating degree illustrated in Fig. 3 (or Figs. 4
and 5) is set.
[0058] The intermediate cooling control is executed when the refrigeration request degree
is smaller as compared with the refrigeration request degree for the supercooling
control. In the intermediate cooling control, while the first expansion mechanism
3 is controlled to have the opening degree according to the refrigeration request
degree, the bypass expansion mechanism 17 and the second expansion mechanism 13 are
closed. Further, the second compressor 11 is stopped. Therefore, the air supplied
into the freezer is cooled only by first evaporator 4. At this time, since the first
refrigerant is not supercooled by the supercooling heat exchanger 14, the refrigeration
capacity is reduced as compared with the supercooling control.
[0059] In the intermediate cooling control, the first expansion mechanism 3 is controlled
according to the refrigeration request degree. Thus, when the refrigeration request
degree gradually decreases in the intermediate cooling control, the opening degree
of the first expansion mechanism 3 also decreases accordingly. The first compressor
1 may be stopped when the first expansion mechanism 3 is reduced to the minimum opening
degree (or a predetermined opening degree set in advance). However, since disturbance
of control may be induced when the first compressor 1 is stopped, a first bypass flow
path 3 1 and a second bypass flow path 32 illustrated in Fig. 8 may be provided in
the main refrigeration circuit 15, and the first compressor 1 may be continuously
operated. In this case, the operation of the first compressor 1 can be continued even
in a state where the first expansion mechanism 3 is extremely narrowed.
[0060] The first bypass flow path 31 is a flow path for allowing the refrigerant (liquid
refrigerant) flowing out of the first condenser 2 to flow into the first compressor
1 without passing through the first evaporator 4. The second bypass flow path 32 is
a flow path for allowing the refrigerant (gas refrigerant) discharged from the first
compressor 1 to flow into the first compressor 1 without passing through the first
condenser 2 and the first evaporator 4. Further, by providing the first bypass flow
path 31 and the second bypass flow path 32, the suction pressure of the first compressor
1 does not excessively decrease, and the flow rate of the refrigerant flowing to the
first evaporator 4 can be adjusted until the opening degree of the first expansion
mechanism 3 is closed without the liquid refrigerant not suctioned into the first
compressor 1. The first bypass flow path 31 is provided with a flow rate regulator
33 such as a thermal expansion valve or an electronic expansion valve, and the second
bypass flow path 32 is provided with a bypass valve 34 such as a suction pressure
regulating valve or an electronic expansion valve.
[0061] The weak cooling control is executed when the refrigeration request degree is smaller
as compared with the refrigeration request degree to be subjected to the intermediate
cooling control. In other words, the supercooling control is executed when the received
refrigeration request degree is the first request value and the second request value,
but the weak cooling control is executed when the received refrigeration request degree
is a third request value that is a further smaller value.
[0062] In the weak cooling control, while the first expansion mechanism 3 and the second
expansion mechanism 13 are closed, the bypass expansion mechanism 17 is controlled
to an opening degree according to the refrigeration request degree. Therefore, the
air supplied into the freezer is not cooled by the first evaporator 4 but is cooled
only by the bypass evaporator 5. In this case, the first compressor 1 is stopped.
However, since there is a possibility that disturbance of control is induced when
the first compressor 1 is stopped, the operation of the first compressor 1 may be
continued by providing the first bypass flow path 31 and the second bypass flow path
32 illustrated in Fig. 8. Accordingly, even when the first expansion mechanism 3 is
closed, the first compressor 1 can be continuously operated.
[0063] Therefore, in the present embodiment, when the refrigeration request degree is the
third request value lower than the second request value, the flow rate of the second
refrigerant circulating in the supercooling refrigeration circuit 16 decreases as
compared with the flow rate based on the target superheating degree when the refrigeration
request degree is the second request value. In this case, the bypass expansion mechanism
17 is controlled so that the second refrigerant flows to the bypass flow path 18,
and the first expansion mechanism 3 is controlled so that the first refrigerant does
not flow through the first evaporator 4 in the main refrigeration circuit 15. Thus,
the refrigeration capacity exhibited by the first evaporator 4 decreases, and the
refrigeration capacity is exhibited in the bypass evaporator 5. At this time, since
the capacity of the second compressor 11 is smaller than the capacity of the first
compressor 1, energy required for driving the compressors 1 and 11 are saved. Further,
when the first compressor 1 is stopped, energy is further saved.
[0064] Note that, although descriptions of other configurations, operations, and effects
are omitted, the description of the first embodiment can be applied to the description
of the second embodiment.
(Third Embodiment)
[0065] As illustrated in Fig. 9, in the third embodiment, a low-temperature refrigeration
circuit 19 is connected to the main refrigeration circuit 15 to form a so-called binary
refrigeration circuit. Note that, here, the same components as those in the first
and second embodiments are denoted by the same reference numerals, and a detailed
description thereof will be omitted.
[0066] The main refrigeration circuit 15 is provided with a cascade bypass flow path 35.
One end portion of the cascade bypass flow path 35 is connected between the supercooling
heat exchanger 14 and the first expansion mechanism 3 in the main refrigeration circuit
15, and the other end portion is connected between the first evaporator 4 and the
first compressor 1 in the main refrigeration circuit 15.
[0067] The cascade bypass flow path 35 is provided with a cascade expansion mechanism 8
and a cascade heat exchanger 52. The cascade heat exchanger 52 is disposed on the
downstream side of the cascade expansion mechanism 8 in the cascade bypass flow path
35, and the first refrigerant decompressed by the cascade expansion mechanism 8 flows
into the cascade heat exchanger 52.
[0068] The cascade expansion mechanism 8 includes, for example, an electronic expansion
valve, and is controlled by the controller 100. Note that the cascade expansion mechanism
8 is not limited to an electronic expansion valve. For example, the cascade expansion
mechanism 8 may include a thermal expansion valve. In this case, the cascade expansion
mechanism 8 is not controlled by the controller 100, but is adjusted to an opening
degree according to the temperature of the first refrigerant flowing through the cascade
bypass flow path 35. In this case, temperature detectors 28 and 29 to be described
later are omitted.
[0069] In the cascade bypass flow path 35, temperature detectors 28 and 29 are provided
so as to be located on the upstream side and the downstream side of the cascade heat
exchanger 52.
[0070] The cascade heat exchanger 52 is connected to the low-temperature refrigeration circuit
19. A third refrigerant is sealed in the low-temperature refrigeration circuit 19.
The third refrigerant may be, for example, a refrigerant having a boiling point lower
than that of the first refrigerant, such as R-473A, R508A, or R-23.
[0071] The low-temperature refrigeration circuit 19 is provided with a low-temperature compressor
51, a low-temperature precooler 56, a cascade heat exchanger 52, a low-temperature
expansion mechanism 53, and a low-temperature evaporator 6 in this order.
[0072] The low-temperature compressor 51 includes, for example, a scroll type compression
mechanism, a screw type compression mechanism, or the like, and is configured to drive
the compression mechanism by a motor at a constant rotation speed. Note that the low-temperature
compressor 51 may be configured so that the rotation speed of the motor can be adjusted
by an inverter. Further, the low-temperature compressor 51 may include one unit compressor,
but may alternatively include two or more unit compressors connected in parallel and
having different capacities.
[0073] The low-temperature precooler 56 is configured to exchange heat of the third refrigerant
discharged from the low-temperature compressor 51 with a cooling medium such as air,
water, or a refrigerant to precool the third refrigerant.
[0074] The cascade heat exchanger 52 causes heat exchange between the first refrigerant
having a low temperature in the cascade expansion mechanism 8 and the third refrigerant
precooled by the low-temperature precooler 56. Thus, the third refrigerant is supercooled.
[0075] The low-temperature expansion mechanism 53 is configured to expand the third refrigerant
condensed in the cascade heat exchanger 52.
[0076] The low-temperature expansion mechanism 53 includes, for example, an electronic expansion
valve. Thus, by adjusting the valve opening degree of the low-temperature expansion
mechanism 53, it is possible to arbitrarily change the flow rate of the third refrigerant
flowing through the cascade heat exchanger 52 and the low-temperature evaporator 6
in the low-temperature refrigeration circuit 19. The opening degree of the low-temperature
expansion mechanism 53 is controlled by the controller 100. That is, the refrigeration
capacity control unit 106 is configured to control the low-temperature expansion mechanism
53 in accordance with the refrigeration request degree.
[0077] The low-temperature evaporator 6 exchanges heat between the third refrigerant in
a liquid state decompressed by the low-temperature expansion mechanism 53 and air
supplied into the freezer to evaporate the third refrigerant. Note that, when the
refrigeration apparatus 10 is provided in a chiller that generates cooling water,
the low-temperature evaporator 6 evaporates the third refrigerant to cool the antifreeze
liquid.
[0078] The function of the controller 100 includes a second superheating degree deriving
unit 107 that calculates the degree of superheat of the first refrigerant flowing
out of the cascade heat exchanger 52 from the difference between the temperatures
detected by the temperature detectors 28 and 29.
[0079] Further, the function of the controller 100 includes a cascade control unit 108 that
controls the cascade expansion mechanism 8 based on the degree of superheat of the
first refrigerant obtained by the second superheating degree deriving unit 107. That
is, the cascade control unit 108 controls the cascade expansion mechanism 8 so that
the degree of superheat of the first refrigerant on the outlet side of the cascade
heat exchanger 52 becomes the target superheating degree. The target superheating
degree of the first refrigerant is a constant value. Thus, the cascade expansion mechanism
8 is controlled so that the flow rate of the first refrigerant in the cascade bypass
flow path 35 increases when the heat load applied to the low-temperature evaporator
6 is high and the heat load of the third refrigerant flowing through the cascade heat
exchanger 52 increases.
[0080] The controller 100 determines whether to perform the binary refrigeration operation
or the primary refrigeration operation according to the set temperature or the operating
condition. In the primary refrigeration operation, since the operation is performed
as in the second embodiment, the description thereof is omitted here. In the binary
refrigeration operation, since the first expansion mechanism 3 and the bypass expansion
mechanism 17 are closed, the first evaporator 4 and the bypass evaporator 5 do not
function. Further, the cascade heat exchanger 52 functions to cause the main refrigeration
circuit 15 to become a cascade circuit, and the supercooling heat exchanger 14 functions
to cause the supercooling refrigeration circuit 16 to become a supercooling circuit.
In this case, the second expansion mechanism 13 and the low-temperature expansion
mechanism 53 are controlled according to the refrigeration request degree. That is,
the controller 100 controls the second expansion mechanism 13 and the low-temperature
expansion mechanism 53 so that the opening degrees of the second expansion mechanism
13 and the low-temperature expansion mechanism 53 decrease as the refrigeration request
degree decreases. Thus, in the low-temperature refrigeration circuit 19 and the supercooling
refrigeration circuit 16, the refrigerant circulation amount corresponding to the
refrigeration request degree can be obtained. Note that the second compressor 11 may
be stopped after the opening degree of the second expansion mechanism 13 decreases
to the minimum opening degree or when the second expansion mechanism 13 is closed.
[0081] Note that, although descriptions of other configurations, operations, and effects
are omitted, the description of the first and second embodiments can be applied to
the description of the third embodiment.
(Fourth Embodiment)
[0082] Fig. 10 illustrates a fourth embodiment. Note that, here, the same components as
those of the first to third embodiments are denoted by the same reference numerals,
and a detailed description thereof will be omitted.
[0083] The fourth embodiment is an example in which the refrigeration apparatus 10 is applied
to an environment forming apparatus 60 such as an environment testing apparatus. The
environment forming apparatus 60 includes an environment chamber 61 and adjusts the
inside of the environment chamber 61 to a predetermined temperature environment. The
environment forming apparatus 60 further includes an air-conditioning chamber 62 for
generating air whose temperature is adjusted, and the first evaporator 4 of the refrigeration
apparatus 10 is disposed in the air-conditioning chamber 62. Note that, in the refrigeration
apparatus 10 described in the second embodiment, the bypass evaporator 5 is also disposed
in the air-conditioning chamber 62. In the refrigeration apparatus 10 described in
the third embodiment, the bypass evaporator 5 and the low-temperature evaporator 6
are also disposed in the air-conditioning chamber 62.
[0084] In the air-conditioning chamber 62, a heater 64 for heating the air and a blower
65 for blowing out the temperature-adjusted air to the environment chamber 61 are
disposed on the downstream side of the first evaporator 4. In the environment chamber
61, the sensor 121 for detecting a temperature of the object to be cooled (or room
temperature of the environment chamber 61) is installed. The input device 122 is used
to input a set temperature of the temperature in the environment chamber 61. The environment
forming apparatus 60 can set a wide range of temperatures such as a negative temperature
range, a normal temperature range, or a high temperature range, and may have a program
operation function of changing a plurality of temperatures stepwise or continuously.
[0085] Note that the environment forming apparatus 60 may be configured to obtain not only
a predetermined temperature environment but also a predetermined humidity environment.
In this case, a humidifier (not illustrated) is provided. In this case, the first
evaporator 4 can also function as a dehumidifier. Further, in the refrigeration apparatus
10 including the second evaporator 5, the second evaporator 5 can also function as
a dehumidifier.
[0086] The generator 120 calculates the refrigeration request degree using the detection
temperature by the sensor 121 and the set temperature from the input device 122.
[0087] The output of the heater 64 is controlled based on the detection temperature by the
sensor 121 and the set temperature from the input device 122. That is, the predetermined
refrigeration capacity is exhibited by the control of the first expansion mechanism
3 and the second expansion mechanism 13 of the refrigeration apparatus 10, but the
temperature detected by the sensor 121 may be lower than the set temperature. At this
time, the room temperature of environment chamber 61 is finely adjusted by the heater
64. Thus, if excessive cooling by the refrigeration apparatus 10 can be suppressed,
not only the electric power of the refrigeration apparatus 10 can be suppressed, but
also the electric power of the heater 64 can be suppressed. In this regard, when the
refrigeration request degree is small, the circulation amount of the refrigerant can
be further reduced by the second expansion mechanism 13, and the refrigeration capacity
can be reduced. Therefore, the electric power of the heater 64 can also be suppressed,
and further energy saving can be achieved. In addition, since the target superheating
degree of the second refrigerant on the outlet side of the supercooling heat exchanger
14 is changed by the superheating degree setting unit 103, and the superheating degree
control unit 104 controls the second expansion mechanism 13 based on the target superheating
degree, both followability to a set temperature and energy saving after the temperature
is reached can be obtained, which is particularly preferable when a program operation
is executed. Note that the heater 64 can be omitted.
[0088] Note that, although descriptions of other configurations, operations, and effects
are omitted, the description of the first to third embodiments can be applied to the
description of the fourth embodiment.
(Other Embodiments)
[0089] It should be understood that the embodiment disclosed herein is illustrative in all
respects and is not restrictive. The present invention is not limited to the above
embodiments, and various modifications, improvements, and the like can be made without
departing from the gist of the present invention. For example, in the above embodiment,
the controller 100 controls the first expansion mechanism 3 based on the refrigeration
request degree, but instead, the controller may control the first expansion mechanism
3 based on the degree of supercool of the first refrigerant at the outlet of the supercooling
heat exchanger 14.
[0090] In addition, although not illustrated, the same function as the first bypass flow
path 31 and the second bypass flow path 32 of the main refrigeration circuit 15 may
also be provided in the supercooling refrigeration circuit 16 of Figs. 1, 7, 8, and
9. In this case, further energy saving is possible. That is, a bypass flow path for
allowing the refrigerant (liquid refrigerant) flowing out of the second condenser
12 to flow into the second compressor 11 without passing through the supercooling
heat exchanger 14 may be provided. In addition, a bypass flow path may be provided
for allowing the refrigerant (gas refrigerant) discharged from the second compressor
11 to flow into the second compressor 11 without passing through the second condenser
12 and the bypass evaporator 5.
[0091] In addition, when the first compressor 1 is configured so that the rotation speed
of the motor can be adjusted by the inverter, the controller 100 may control the motor
rotation speed of the first compressor 1 based on the refrigeration request degree
instead of controlling the first expansion mechanism 3.
Here, the embodiments will be outlined.
[0092]
- (1) A refrigeration apparatus according to the embodiment includes a main refrigeration
circuit in which a first refrigerant is sealed and which is provided with a first
compressor, a first condenser, a supercooling heat exchanger, a first expansion mechanism,
and a first evaporator, a supercooling refrigeration circuit in which a second refrigerant
is sealed and which is provided with a second compressor, a second condenser, and
a second expansion mechanism and which is connected to the supercooling heat exchanger,
and a controller configured to execute superheating degree setting control and superheating
degree control. The supercooling heat exchanger is configured to supercool the first
refrigerant in the main refrigeration circuit by evaporation of the second refrigerant
in the supercooling refrigeration circuit. The controller is configured to set, in
the superheating degree setting control, a target value of a degree of superheat of
the second refrigerant on an outlet side of the supercooling heat exchanger to a first
value when a refrigeration request degree is a first request value, and set the target
value of the degree of superheat to a second value larger than the first value when
the refrigeration request degree is a second request value smaller than the first
request value. The controller is configured to control, in the superheating degree
control, the second expansion mechanism based on the target value of the degree of
superheat set by the superheating degree setting control.
[0093] In the refrigeration apparatus, the supercooling heat exchanger supercools the first
refrigerant in the main refrigeration circuit by evaporating the second refrigerant
in the supercooling refrigeration circuit. Thus, a refrigeration capacity exhibited
by the main refrigeration circuit is increased accordingly. Therefore, as compared
with a case where only one refrigeration circuit exhibits an equivalent refrigeration
capacity, a compressor having a smaller compressor capacity can exhibit the equivalent
refrigeration capacity. Further, when a value of the refrigeration request degree
is the second request value (when the value of the refrigeration request degree is
smaller than the first request value), the target value of the degree of superheat
of the second refrigerant on the outlet side of the supercooling heat exchanger is
set to the second value (a value larger than the first value). Then, the second expansion
mechanism is controlled based on the target value of the degree of superheat of the
second refrigerant on the outlet side of the supercooling heat exchanger. Thus, a
flow rate of the second refrigerant circulating in the supercooling refrigeration
circuit decreases as compared with a flow rate based on the target value of the degree
of superheat when the refrigeration request degree is the first request value. Thus,
power of the second compressor of the supercooling refrigeration circuit decreases
as compared with that in a case where the target value of the degree of superheat
is controlled to be constant, so that the supercooling refrigeration circuit can further
save energy when the refrigeration request degree is relatively small.
[0094] (2) The controller may be configured to set the target value of the degree of superheat
to a minimum value in the superheating degree setting control when the refrigeration
request degree is a maximum request value.
[0095] In this aspect, since the target value of the degree of superheat becomes the minimum
value when the refrigeration request degree is the maximum request value, the second
expansion mechanism is controlled based on the target value of the degree of superheat,
so that the flow rate of the second refrigerant circulating through the supercooling
refrigeration circuit is maximized. Thus, a degree of supercool of the first refrigerant
on the outlet side of the supercooling heat exchanger in the main refrigeration circuit
also increases. Therefore, a larger refrigeration capacity can be exhibited.
[0096] (3) The controller may be configured to set, in the superheating degree setting control,
the target value of the degree of superheat to the first value when the refrigeration
request degree is equal to or more than a preset threshold, and gradually increase
the target value of the degree of superheat from the first value as the refrigeration
request degree decreases when the refrigeration request degree is less than the threshold.
[0097] According to this aspect, a predetermined refrigeration capacity is exhibited when
the refrigeration request degree is equal to or more than the threshold, and further
energy saving of the supercooling refrigeration circuit can be achieved as the refrigeration
request degree decreases at a time of stabilization when the refrigeration request
degree is less than the threshold.
[0098] (4) The controller may be configured to gradually increase, in the superheating degree
setting control, the target value of the degree of superheat from the first value
as the refrigeration request degree decreases. In this case, the controller may be
configured to stop the second compressor after gradually increasing the target value
of the degree of superheat from the first value.
[0099] In this aspect, the second compressor stops when the refrigeration request degree
decreases, so that energy saving can be further achieved in the supercooling refrigeration
circuit.
[0100] (5) The degree of superheat may be obtained from a temperature difference of the
second refrigerant flowing-in and flowing-out the supercooling heat exchanger in the
supercooling refrigeration circuit.
[0101] (6) A bypass flow path may be connected to the supercooling refrigeration circuit
so as to bypass the supercooling heat exchanger. In this case, the bypass flow path
may be provided with a bypass expansion mechanism and a bypass evaporator. In addition,
a capacity of the second compressor may be smaller than a capacity of the first compressor.
The controller may be configured to control the first expansion mechanism so that
the first refrigerant does not flow through the first evaporator and control the bypass
expansion mechanism so that the second refrigerant flows through the bypass evaporator
when the refrigeration request degree is a third request value smaller than the second
request value.
[0102] In this aspect, when the refrigeration request degree is the third request value
smaller than the second request value, the flow rate of the second refrigerant circulating
in the supercooling refrigeration circuit decreases as compared with the flow rate
when it is based on the target value of the degree of superheat when the refrigeration
request degree is the second request value. In this case, the first expansion mechanism
is controlled so that the first refrigerant does not flow through the first evaporator
in the main refrigeration circuit, and the bypass expansion mechanism is controlled
so that the second refrigerant flows through the bypass flow path in the supercooling
refrigeration circuit. Thus, a refrigeration capacity exhibited by the first evaporator
decreases, and a refrigeration capacity is exhibited in the bypass evaporator. At
this time, since the capacity of the second compressor is smaller than the capacity
of the first compressor, energy required for driving the compressor is saved.
[0103] (7) The environment forming apparatus according to the embodiment includes an environment
chamber and the refrigeration apparatus for cooling an inside of the environment chamber.
[0104] In the environment forming apparatus, when the refrigeration request degree is low,
the target value of the degree of superheat in the refrigeration apparatus is increased,
so that the flow rate of the second refrigerant in the supercooling refrigeration
circuit decreases. Thus, the power of the second compressor of the supercooling refrigeration
circuit decreases as compared with that in a case where the target value of the degree
of superheat is controlled to be constant. Moreover, the refrigeration capacity of
the main refrigeration circuit is also smaller as compared with that in a case where
the target value of the degree of superheat is controlled to be constant. Therefore,
energy saving can be achieved.
[0105] (8) The environment forming apparatus may further include a heater configured to
operate when a temperature of air in the environment chamber is lower than a predetermined
temperature. In this aspect, when the target value of the degree of superheat is increased
in a case where the refrigeration request degree is low, the flow rate of the second
refrigerant in the supercooling refrigeration circuit decreases. Thus, the refrigeration
capacity of the main refrigeration circuit is also smaller as compared with that in
a case where the target value of the degree of superheat is controlled to be constant.
Accordingly, the temperature of the air in the environment chamber is suppressed from
excessively decreasing, so that the output of the heater can be reduced. Therefore,
further energy saving can be achieved.
[0106] (9) A refrigeration method according to the embodiment is a refrigeration method
using a refrigeration apparatus, the refrigeration apparatus including a main refrigeration
circuit in which a first refrigerant is sealed and which is provided with a first
compressor, a first condenser, a supercooling heat exchanger, a first expansion mechanism,
and a first evaporator, and a supercooling refrigeration circuit in which a second
refrigerant is sealed and which is provided with a second compressor, a second condenser,
and a second expansion mechanism and which is connected to the supercooling heat exchanger,
the refrigeration method comprising: receiving a refrigeration request degree in the
refrigeration apparatus; setting a target value of a degree of superheat of the second
refrigerant on an outlet side of the supercooling heat exchanger to a first value
when the received refrigeration request degree is a first request value; setting a
target value of the degree of superheat to a second value larger than the first value
when the received refrigeration request degree is a second request value smaller than
the first request value; controlling the second expansion mechanism based on the set
target value of the degree of superheat; and supercooling the first refrigerant in
the main refrigeration circuit by evaporation of the second refrigerant in the supercooling
heat exchanger into which the second refrigerant having a flow rate adjusted by the
second expansion mechanism flows.
[0107] As described above, according to the above embodiment, not only energy saving can
be achieved by using the supercooling heat exchanger, but also further energy saving
can be achieved.