WO2008001667A1

WO2008001667A1 - Refrigeration device

Info

Publication number: WO2008001667A1
Application number: PCT/JP2007/062442
Authority: WO
Inventors: Satoru Sakae; Masaaki Takegami; Hiroto Nakajima; Iwao Shinohara
Original assignee: Daikin Industries, Ltd.
Priority date: 2006-06-30
Filing date: 2007-06-20
Publication date: 2008-01-03
Also published as: TW200817643A; JP4096984B2; JP2008008593A

Abstract

A refrigeration device having a super cooling circuit (1a) for enhancing cooling ability and a main refrigerant circuit (1b) for cooling a target cooling space. Even if the refrigeration device is not in an overloaded condition, high pressure equivalent control in which the pressure of a high pressure refrigerant in the main refrigerant circuit (1b) and the pressure of a high pressure refrigerant in the super cooling circuit (1a) are brought closer to each other is performed in order to improve the performance coefficient of the refrigeration device. Such control is performed by operating a second variable displacement compressor (20) for controlling the super cooling ability of the super cooling circuit (1a).

Description

Specification

Refrigeration equipment

Technical field

TECHNICAL FIELD [0001] The present invention relates to a refrigeration apparatus provided with a supercooling circuit, and particularly to a technology for controlling the capacity of a supercooling circuit.

Background art

Conventionally, a refrigeration apparatus including a refrigerant circuit that performs a vapor compression refrigeration cycle is known. In some of these refrigeration apparatuses, a main cooling circuit for cooling a space to be cooled is provided with a supercooling circuit including a supercooling heat exchanger for increasing the cooling capacity.

[0003] Specifically, in the main refrigerant circuit of the refrigeration apparatus, a first compressor, a first outdoor heat exchanger, a first expansion valve, and an indoor heat exchanger are sequentially connected by a refrigerant pipe. On the other hand, in the supercooling circuit, the second compressor, the second outdoor heat exchanger, the second expansion valve, and the supercooling heat exchanger are sequentially connected by the refrigerant pipe. When the supercooling circuit is attached to the main refrigerant circuit, the supercooling heat exchanger of the supercooling circuit is provided between the first outdoor heat exchanger of the main refrigerant circuit and the first expansion valve. Place in high pressure liquid piping. The supercooling heat exchanger is a heat exchanger that exchanges heat between refrigerants, and includes a first flow path through which the refrigerant in the main refrigerant circuit flows and a second flow path through which the refrigerant in the supercooling circuit flows. As a result, in the supercooling heat exchanger, the high-pressure liquid refrigerant condensed in the first outdoor heat exchanger of the main refrigerant circuit and the low-pressure refrigerant in the supercooling circuit are heat-exchanged, so that the high-pressure liquid refrigerant is superfluid. By cooling, the degree of supercooling of the high-pressure liquid refrigerant can be increased. And by increasing the degree of supercooling of the high-pressure liquid refrigerant, the cooling capacity of the main refrigerant circuit can be increased. Patent Document 1 is cited as a conventional technique for controlling the supercooling circuit in the refrigeration apparatus having the supercooling circuit.

[0004] In the refrigeration apparatus of Patent Document 1, the first compressor of the main refrigerant circuit is composed of a variable capacity compressor, and the operating capacity of the first compressor and the low-pressure refrigerant pressure of the main refrigerant circuit are adjusted. Based on this, on / off control of the second compressor of the supercooling circuit is performed. Specifically, the above capacity When the capacity of the variable compressor is equal to or greater than the first predetermined value and the low-pressure refrigerant pressure is equal to or greater than the predetermined value, that is, when the main refrigerant circuit is in a cooling overload state, the second compressor of the supercooling circuit is to start. On the other hand, when the capacity of the variable capacity compressor becomes equal to or lower than a second predetermined value lower than the first predetermined value, the second compressor of the supercooling circuit stops.

[0005] That is, the start / stop control is performed when the second compressor of the supercooling circuit starts when the main refrigerant circuit is in a cooling overload state, and does not enter the cooling overload state. Is configured to stop.

Patent Document 1: Japanese Patent No. 3376844

Disclosure of the invention

Problems to be solved by the invention

However, in the refrigeration apparatus disclosed in Patent Document 1, although the overload state of the main refrigerant circuit can be avoided by using the overcooling circuit, the main refrigerant circuit is in an overload state. Otherwise, the supercooling circuit will not start. That is, the supercooling circuit is merely configured as an auxiliary unit only to compensate for the lack of cooling capacity of the main refrigerant circuit. For example, in the operation of the refrigeration system, the main refrigerant circuit is at a higher pressure than normal due to a rise in outside air temperature, and the input to the variable capacity compressor of the main refrigerant circuit becomes excessive, resulting in a decrease in the coefficient of performance. Even in the running operation, if the low-pressure refrigerant pressure in the main refrigerant circuit is maintained, the second compressor of the supercooling circuit of the refrigeration apparatus in Patent Document 1 does not start.

[0007] The present invention has been made in view of power, and an object of the present invention is to provide a refrigeration apparatus including a supercooling circuit for increasing the cooling capacity, in which the refrigeration apparatus is not in an overload state. The other is to improve the coefficient of performance of the refrigeration system by actively operating the compressor of the supercooling circuit.

Means for solving the problem

[0008] The first invention provides a variable capacity first compressor (2), a first condenser (6), a supercooling heat exchanger (8), a first expansion mechanism (10), and a first evaporator ( 12) are connected in sequence to perform a refrigeration cycle, a main refrigerant circuit (lb), a second compressor (20), a second condenser (24), a second expansion mechanism (26), and the above supercooling heat exchanger (8) are connected in order to perform a refrigeration cycle (la) and the first compression It assumes a refrigeration system equipped with a first capacity adjusting means capable of adjusting the capacity of the machine (2).

[0009] The second compressor (20) includes a variable capacity compressor (20), and the main refrigerant circuit

first high pressure refrigerant pressure detecting means (5) for detecting the high pressure refrigerant pressure of (lb), second high pressure refrigerant pressure detecting means (23) for detecting the high pressure refrigerant pressure of the supercooling circuit (la), and the above A second capacity adjusting means capable of adjusting the capacity of the second compressor (20), and controlling the first capacity adjusting means and the second capacity adjusting means to control the main refrigerant circuit (lb). It is characterized by comprising high-pressure equivalent control means (32) for bringing the high-pressure refrigerant pressure value close to the high-pressure refrigerant pressure value of the supercooling circuit (la).

[0010] In the first invention, the high-pressure equivalent control means (32) can reduce the capacity of the first compressor (2) with the high-pressure refrigerant pressure of the supercooling circuit (la) as a target value. The high-pressure equivalent control means (32) can increase the capacity of the second compressor (20) with the high-pressure refrigerant pressure in the main refrigerant circuit (lb) as a target value. Thereby, the high-pressure refrigerant pressure values of the main refrigerant circuit (lb) and the supercooling circuit (la) can be made closer.

[0011] Here, regarding the cooling capacity of the main refrigerant circuit (lb) when both of the high-pressure refrigerant pressure values approach, the capacity of the first compressor (2) decreases, so that the main refrigerant circuit ( The amount of refrigerant flowing into the first evaporator (12) of lb) decreases, and the cooling capacity of the main refrigerant circuit (lb) decreases. On the other hand, as the capacity of the second compressor (20) increases, the supercooling capacity in the supercooling heat exchanger (8) of the main refrigerant circuit (1 b) increases, and the main refrigerant circuit (lb ), The degree of supercooling of the refrigerant flowing through it increases. This expansion of the degree of supercooling increases the cooling capacity of the main refrigerant circuit (lb).

[0012] A second invention comprises, in the first invention, an outlet liquid temperature detecting means (9) for detecting a refrigerant outlet liquid temperature on the main refrigerant circuit (lb) side of the supercooling heat exchanger (8). The high-pressure equivalent control means (32) increases the capacity of the second compressor (20) by controlling the second capacity adjusting means if the refrigerant outlet liquid temperature is higher than a predetermined value, If it is lower than the value, the second capacity adjusting means is controlled to reduce the capacity of the second compressor (20).

[0013] In the second invention, the set value at the refrigerant outlet liquid temperature of the main refrigerant circuit (lb), which is obtained only by the high pressure refrigerant pressure value of the main refrigerant circuit (lb), is used as a target value, and The first control unit of the stage (32) can control the capacity of the second compressor (20).

[0014] A third invention is the first or second invention, comprising suction refrigerant pressure detection means (28) for detecting the suction refrigerant pressure of the second compressor (20), wherein the high-pressure equivalent control means (32) controls the second capacity adjusting means to increase the capacity of the second compressor (20) if the suction refrigerant pressure is higher than a predetermined value, and if the suction refrigerant pressure is lower than the predetermined value, It is characterized by comprising a second control unit that controls the adjusting means to reduce the capacity of the second compressor (20).

[0015] In the third invention, the suction of the second compressor (20) includes only the high-pressure refrigerant pressure value of the main refrigerant circuit (lb) and the set value of the refrigerant outlet liquid temperature of the main refrigerant circuit (lb). The second controller of the high-pressure equivalent control means (32) can control the capacity of the second compressor (20) using the set value for the refrigerant pressure as a target value.

[0016] A fourth invention is the four inventions according to any one of the first to third powers, further comprising an evaporation temperature detecting means (11) for detecting an evaporation temperature of the main refrigerant circuit (lb), wherein the high-pressure equivalent control means (32) If the evaporation temperature is lower than a predetermined value, the first capacity adjustment means is controlled to reduce the capacity of the first compressor (2), and if higher than the predetermined value, the first capacity adjustment is performed. A third control unit that increases the capacity of the first compressor (2) by controlling the means is provided.

[0017] In the fourth invention, the high-pressure equivalent control means (32) using as a target a set value at the evaporation temperature of the main refrigerant circuit (lb), which is not only the high-pressure refrigerant pressure value of the supercooling circuit (la). The third control unit can control the capacity of the first compressor (2).

The invention's effect

[0018] According to the present invention, by performing the high-pressure equivalent control, the supercooling circuit (la) until the high-pressure refrigerant pressure of the supercooling circuit (la) approaches the high-pressure refrigerant pressure of the main refrigerant circuit (lb). 1) The second compressor (20) of a) can be operated. As a result, even if the main refrigerant circuit (lb) is not overloaded, the second compressor (20) of the supercooling circuit (la) can be operated. As a result, the cooling load of the refrigeration system can be reduced. The main refrigerant circuit (lb) and the supercooling circuit (la) can be shared. Here, regarding the sharing of the cooling load, the decrease in the cooling capacity of the main refrigerant circuit (lb) due to the decrease in the capacity of the first compressor (2) It becomes a configuration to compensate for the increase in cooling capacity due to the increase in capacity.

[0019] The increase in the electric input due to the increase in the capacity of the second compressor (20) is the decrease in the electric input of the first compressor (2) due to the decrease in the cooling capacity of the main refrigerant circuit (lb). Smaller than. This is because the coefficient of performance of the supercooling circuit (la) is larger than the coefficient of performance of the main refrigerant circuit (lb). Here, the reason why the coefficient of performance of the supercooling circuit (la) is larger than that of the main refrigerant circuit (lb) is that, for example, when the set temperature of the cooling target space is -30 ° C, the main refrigerant circuit (lb) The evaporation saturation temperature is around 140 ° C, the evaporation saturation temperature of the supercooling circuit (la) is around 0 ° C, and the low-pressure refrigerant pressure in the supercooling circuit (la) is high. If high-pressure equivalent control is performed while maintaining this low-pressure state, when both high-pressure refrigerant pressures have the same value, the performance coefficient of the supercooling circuit (la) with a small high-low-pressure difference is greater in the main refrigerant circuit (lb). It is because it becomes large compared.

[0020] As described above, the cooling operation is not performed only by the main refrigerant circuit (lb) having a small coefficient of performance. The cooling operation is shared by the main refrigerant circuit (lb) and the supercooling circuit (la) having a large coefficient of performance. By performing this, the total coefficient of performance of the refrigeration apparatus can be improved.

[0021] Further, according to the second invention, during the high-pressure equivalent control, the first controller of the high-pressure equivalent control can limit an increase in capacity in the second compressor (20). . Here, the reason for limiting the increase in the capacity of the second compressor (20) is that when the capacity of the second compressor (20) is increased, the high-pressure refrigerant pressure in the supercooling circuit (la) increases. This is because the supercooling capacity of the supercooling heat exchanger (8) is increased and the refrigerant outlet liquid temperature of the supercooling heat exchanger (8) of the main refrigerant circuit (lb) is also lowered. That is, as in the first invention, when the high-pressure equivalent means increases the capacity of the second compressor (20) by using only the high-pressure refrigerant pressure of the main refrigerant circuit (lb) as a target value, depending on conditions, It is conceivable that the above-mentioned refrigerant outlet liquid temperature is excessively lower than necessary. Therefore, in order to prevent the refrigerant outlet liquid temperature from dropping too much, the first control unit limits the increase in capacity of the second compressor (20).

[0022] Further, according to the third aspect of the invention, during the high pressure equivalent control, the second controller of the high pressure equivalent control can limit an increase in capacity in the second compressor (20). . Here, the reason for limiting the increase in the capacity of the second compressor (20) is that when the capacity of the second compressor (20) is increased, the high-pressure refrigerant pressure in the supercooling circuit (la) increases. ,Up This is because the suction refrigerant pressure of the second compressor (20) also decreases. That is, when the high pressure equivalent means increases the capacity of the second compressor (20) with only the high pressure refrigerant pressure of the main refrigerant circuit (lb) as a target value as in the first invention, Depending on the situation, it is conceivable that the suction refrigerant pressure is too low. Therefore, in order to prevent the suction refrigerant pressure from dropping too much, the second control unit limits the increase in capacity of the second compressor (20).

[0023] Further, according to the fourth aspect of the invention, during the high pressure equivalent control, the third controller of the high pressure equivalent control has a capacity of the first compressor (2) based on the evaporation temperature. The reduction can be limited. Here, the reason for limiting the capacity reduction of the first compressor (2) is that when the capacity of the first compressor (2) is decreased, the cooling capacity of the main refrigerant circuit (lb) decreases and the cooling capacity of the first compressor (2) decreases. This is because the target space is insufficiently cooled. That is, as in the first invention, when the high-pressure equivalent means reduces the capacity of the first compressor (2) by using only the high-pressure refrigerant pressure of the supercooling circuit (la) as a target value, depending on the conditions, It is conceivable that the evaporation temperature is too high. Therefore, in order to prevent the intake refrigerant pressure from rising excessively, the three control units limit the decrease in the capacity of the first compressor (2). As a result, the high-pressure equivalent control means (32) can perform high-pressure equivalent control while maintaining the cooling capacity of the main refrigerant circuit (lb).

Brief Description of Drawings

FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to an embodiment.

FIG. 2 is a control flow diagram of the refrigeration apparatus according to the embodiment.

FIG. 3 is a table showing the relationship between the condensation temperature of the main refrigerant circuit and the subcooling circuit and the coefficient of performance of the refrigeration apparatus.

Explanation of symbols

[0025] 1 Refrigeration equipment

la Supercooling circuit

lb Main refrigerant circuit

2 First variable capacity compressor (first compressor)

5 First high-pressure refrigerant pressure sensor (first high-pressure refrigerant pressure detection means) 6 Outdoor heat exchanger (first condenser)

8 Supercooling heat exchanger

9 Refrigerant outlet liquid temperature sensor (outlet liquid temperature detection means)

10 1st expansion valve (1st expansion mechanism)

11 Evaporation temperature sensor (Evaporation temperature detection means)

12 Indoor heat exchanger (first evaporator)

20 Second variable capacity compressor (second compressor)

23 Second high-pressure refrigerant pressure sensor (second high-pressure refrigerant pressure detection means)

24 Second outdoor heat exchanger (second condenser)

26 Second expansion valve (second expansion mechanism)

28 Second low-pressure refrigerant pressure sensor (intake refrigerant pressure detection means)

32 Controller (High-pressure equivalent control means)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0027] Configuration of refrigeration apparatus

FIG. 1 is a refrigerant circuit diagram of the refrigeration apparatus according to this embodiment. This refrigeration apparatus is for cooling a space to be cooled (for example, a freezing room). The refrigeration apparatus includes a main refrigerant circuit (lb) for cooling the space to be cooled, and a supercooling heat exchanger (8) for cooling the refrigerant (high-pressure liquid refrigerant) flowing through the main refrigerant circuit (lb). And a supercooling circuit (la). The refrigerating apparatus is provided with a controller (high pressure equivalent control means) (32) for controlling the operation of the main refrigerant circuit (lb) and the supercooling circuit (la).

The main refrigerant circuit (lb) includes a first variable capacity compressor (first compressor) (2), a first outdoor heat exchanger (first condenser) (6), and the supercooling heat exchanger ( 8) and the first expansion valve (first expansion mechanism) (10) and the indoor heat exchanger (first evaporator) (12) are connected in order by refrigerant piping so that a vapor compression refrigeration cycle is performed. It is composed.

[0029] An inverter (not shown) is connected to the first variable capacity compressor (2). The inverter supplies current to the first variable capacity compressor (2) and supplies the current. The flow frequency can be changed. That is, the capacity of the first variable capacity compressor (2) can be freely changed within a certain range by the inverter. On the other hand, the first suction refrigerant pipe (15) is connected to the suction side of the first variable displacement compressor (2), and the first discharge refrigerant pipe (3) is connected to the discharge side. The first suction refrigerant pipe (15) is provided with a first suction temperature sensor (17) and a first low-pressure refrigerant pressure sensor (16). The first discharge refrigerant pipe (3) is provided with a first discharge temperature sensor (4) and a first high-pressure refrigerant pressure sensor (first high-pressure refrigerant pressure detection means) (5). The first discharge refrigerant pipe (3) connects the first variable capacity compressor (2) and the first outdoor heat exchanger (6).

[0030] The first outdoor heat exchanger (6) is a cross-fin type fin-and-tube heat exchanger, and in the vicinity of the first outdoor heat exchanger (6) One blower fan (6a) and a first outside air temperature sensor (6b) are provided. Although not shown, in the first outdoor heat exchanger (6), the heat transfer tubes are arranged in a plurality of paths, and a large number of aluminum fins are installed perpendicular to the heat transfer tubes. The first high-pressure liquid refrigerant pipe (7) connecting the first outdoor heat exchanger (6) and the first expansion valve (10) is provided with the supercooling heat exchanger (8). Yes.

[0031] The supercooling heat exchanger (8) is composed of a plate fin type heat exchanger, and the first and second flow paths (8a, 8b) are provided in the pre-fin type heat exchanger. Is formed. The refrigerant circulating in the main refrigerant circuit (lb) flows through the first flow path (8a), and the refrigerant circulating through the supercooling circuit (la) flows through the second flow path (8b). The refrigerant exchanges heat to cool the refrigerant flowing on the main refrigerant circuit (lb) side. In addition, a refrigerant outlet liquid temperature sensor (9) (outlet liquid temperature detecting means) for measuring the temperature of the outlet side of the supercooling heat exchanger (8) for the refrigerant flowing through the main refrigerant circuit (1b) side is provided. The refrigerant pipe for connecting the supercooling heat exchanger (8) and the first expansion valve (10) of the main refrigerant circuit (lb) is provided.

[0032] The first expansion valve (10) is an electric expansion valve whose opening degree can be adjusted, and the opening degree can be appropriately changed by an electric signal.

[0033] Similar to the first outdoor heat exchanger (6), the indoor heat exchanger (12) is a cross-fin type fin-and-tube heat exchanger. Although not shown, the heat transfer tubes are arranged in a plurality of paths, and a number of aluminum fins are installed perpendicular to the heat transfer tubes. The An evaporation temperature sensor (evaporation temperature detecting means) (11) is provided on the inlet side of the indoor heat exchanger (12), and a third blower fan (12a) is provided near the indoor heat exchanger (12). ) And an indoor temperature sensor (12b). The indoor heat exchanger (12) and the first variable capacity compressor (2) are connected by the first suction refrigerant pipe (15).

[0034] The main refrigerant circuit (lb) is provided with a liquid injection pipe (18), and one end of the liquid injection pipe (18) is connected to the first outdoor heat exchanger (6) and the excess refrigerant. Connected to the first high-pressure liquid refrigerant pipe (7) between the cooling heat exchanger (8) and the other end between the indoor heat exchanger (12) and the first variable capacity compressor (2). It is connected to the first suction refrigerant pipe (15). The liquid injection pipe (18) is provided with a pressure reducing valve (19) for reducing the pressure of the refrigerant flowing through the liquid injection pipe (18).

The supercooling circuit (la) consists of a second variable capacity compressor (20), a second outdoor heat exchanger (second condenser) (24), and a second expansion valve (second expansion mechanism) (26). And the supercooling heat exchanger (8) are sequentially connected by a refrigerant pipe so as to perform a vapor compression refrigeration cycle.

[0036] Similar to the first variable capacity compressor (2) of the main refrigerant circuit (lb), the second variable capacity compressor (20) is connected to an inverter (not shown). The capacity of the second variable capacity compressor (20) can be freely changed within a certain range. On the other hand, a second suction refrigerant pipe (30) is connected to the suction side of the second variable capacity compressor (20), and a second discharge refrigerant pipe (21) is connected to the discharge side. The second suction refrigerant pipe (30) is provided with a second suction temperature sensor (29) and a second low-pressure refrigerant pressure sensor (suction refrigerant pressure detection means) (28). The second discharge refrigerant pipe (21) is provided with a second discharge temperature sensor (22) and a second high-pressure refrigerant pressure sensor (second high-pressure refrigerant pressure detection means) (23). The second discharge refrigerant pipe (21) connects the second variable capacity compressor (20) and the second outdoor heat exchanger (24).

[0037] The second outdoor heat exchanger (24) is a cross-fin type fin-and-tube heat exchanger similar to the first outdoor heat exchanger (6) of the main refrigerant circuit (lb). In the vicinity of the second outdoor heat exchanger (24), a second blower fan (2½) and a second outside air temperature sensor (24b) are provided. Although not shown, the second outdoor heat exchanger (24) has a plurality of heat transfer tubes. It is arranged in several passes, and a large number of aluminum fins are installed perpendicular to the heat transfer tubes. The second outdoor heat exchanger (24) and the second expansion valve (26) are connected by a second high-pressure liquid refrigerant pipe (25).

[0038] The second expansion valve (26) is an electric expansion valve whose opening degree can be adjusted, and the opening degree can be appropriately changed by an electric signal. The second expansion valve (26) and the supercooling heat exchanger (8) are connected by a second low-pressure refrigerant pipe (27).

[0039] As described above, the supercooling heat exchanger (8) is composed of a plate fin type heat exchanger, and the second channel (8b) in the plate fin type heat exchanger has a second channel (8b). 2 Low pressure refrigerant pipe (27) is connected.

[0040] <Controller>

The controller (32) includes a refrigerant outlet liquid temperature sensor (9), an evaporation temperature sensor (11), a first high-pressure refrigerant pressure sensor (5), and a second high-pressure refrigerant pressure sensor (23) provided in the refrigeration apparatus. In response to the detection signal from the second low-pressure refrigerant pressure sensor (28), the high-pressure equivalent control operation of the first variable capacity compressor (2) and the second variable capacity compressor (20) is performed. Yes.

[0041] Operation of refrigeration equipment

The operation of the refrigeration apparatus of this embodiment will be described. First, the cooling operation of the main refrigerant circuit (lb) and the supercooling circuit (la) will be described, and then the high-pressure equivalent control operation in the main refrigerant circuit (lb) and the supercooling circuit (la) will be described.

In the cooling operation of the main refrigerant circuit (lb), the refrigerant circulates in the circuit using the first outdoor heat exchanger (6) as a condenser and the indoor heat exchanger (12) as an evaporator. The opening of the expansion valve (10) is adjusted to perform the vapor compression refrigeration cycle. Further, the opening degree of the pressure reducing valve (19) of the liquid injection pipe (18) is adjusted according to the operating state.

[0043] When the first variable displacement compressor (2) is started, high-pressure gas refrigerant is discharged from the discharge side of the first variable displacement compressor (2) through the first discharge refrigerant pipe (3). Is done. The discharged high-pressure gas refrigerant flows into the first outdoor heat exchanger (6), radiates heat to the outside air in the first outdoor heat exchanger (6), and condenses to become high-pressure liquid refrigerant. The refrigerant that has become the high-pressure liquid refrigerant flows out of the first outdoor heat exchanger (6) and passes through the first flow path (8a) of the supercooling heat exchanger (8). At this time, it is supercooled and flows out of the supercooling heat exchanger (8).

[0044] The supercooled high-pressure liquid refrigerant flows into the first expansion valve (10). The high-pressure liquid refrigerant that has flowed into the first expansion valve (10) is reduced in pressure when passing through the first expansion valve (10), becomes a low-pressure liquid refrigerant, and flows into the indoor heat exchanger (12). The low-pressure liquid coolant flowing into the indoor heat exchanger (12) absorbs heat from the air in the space to be cooled when passing through the indoor heat exchanger (12). The low-pressure liquid refrigerant that has absorbed heat from the air in the space to be cooled evaporates into a low-pressure gas refrigerant and flows out of the indoor heat exchanger (12). The low-pressure gas refrigerant that has flowed out of the indoor heat exchanger (12) passes through the first suction refrigerant pipe (15) and flows into the first variable capacity compressor (2). The low-pressure gas refrigerant that has flowed into the first variable capacity compressor (2) is compressed to become high-pressure gas refrigerant, and is discharged from the first variable capacity compressor (2) again.

[0045] As described above, the refrigerant circulates in the main refrigerant circuit (lb) to cool the space to be cooled.

In the cooling operation of the supercooling circuit (la), the refrigerant circulates in the circuit using the second outdoor heat exchanger (24) as a condenser and the supercooling heat exchanger (8) as an evaporator. The opening degree of the expansion valve (26) is adjusted to perform the vapor compression refrigeration cycle.

When the second variable capacity compressor (20) is started, high pressure gas refrigerant is discharged from the discharge side of the second variable capacity compressor (20) through the second discharge refrigerant pipe (21). The The discharged high-pressure gas refrigerant flows into the second outdoor heat exchanger (24) and radiates heat to the outside air in the second outdoor heat exchanger (24), and condenses to become a high-pressure liquid refrigerant.

[0048] The high-pressure liquid refrigerant flows out of the second outdoor heat exchanger (24) and flows into the second expansion valve (26). The high-pressure liquid refrigerant flowing into the second expansion valve (26) is reduced in pressure when passing through the second expansion valve (26) to become a low-pressure liquid refrigerant, and the second flow of the supercooling heat exchanger (8). Into the road. The low-pressure liquid refrigerant flowing into the second flow path of the supercooling heat exchanger (8) flows through the first flow path when passing through the second flow path of the supercooling heat exchanger (8). Absorbs heat from the high-pressure liquid refrigerant in the main refrigerant circuit (lb). The low-pressure liquid refrigerant in the second flow path that has absorbed heat from the high-pressure liquid refrigerant in the first flow path evaporates to become a low-pressure gas refrigerant and flows out of the supercooling heat exchanger (8). The low-pressure gas refrigerant that has flowed out of the supercooling heat exchanger (8) passes through the second suction refrigerant pipe (30) and passes through the second possible refrigerant. It flows into the variable capacity compressor (20). The low-pressure gas refrigerant flowing into the second variable capacity compressor (20) is compressed to become high-pressure gas refrigerant, and is discharged from the second variable capacity compressor (20) again.

As described above, the refrigerant circulates in the supercooling circuit (la), and the high-pressure liquid coolant in the main refrigerant circuit (lb) is cooled.

[0050] <High pressure equivalent control operation>

Next, the operation of high-pressure equivalent control in the main refrigerant circuit (lb) and the supercooling circuit (la) will be described based on the control flow in FIG. Here, the high pressure equivalent control means that the main refrigerant circuit (lb) and the supercooling circuit are controlled by performing capacity control by increasing / decreasing the operating frequency of the first and second variable capacity compressors (2, 20). This is a control that adjusts the high-pressure refrigerant pressure with (la) to equalize both high-pressure refrigerant pressures.

[0051] When the cooling operation of the refrigeration apparatus is started, in step ST1, the first outside air temperature sensor

The outside air temperature Ta detected in (6b) is larger than a predetermined value XI (for example, X1 = 20 ° C), and the frequency of the first variable displacement compressor (2) is the first variable displacement compressor ( 2) When the frequency is 50% or more of the maximum frequency, or when the frequency of the first variable displacement compressor (2) is 90% or more of the maximum frequency of the first variable displacement compressor (2) The high-pressure refrigerant pressure P1 detected by the first high-pressure refrigerant pressure sensor (5) in the main refrigerant circuit (lb) is detected by the second high-pressure refrigerant pressure sensor (23) in the supercooling circuit (la). Determine whether pressure is greater than P2. If the high-pressure refrigerant pressure P1 is less than or equal to the high-pressure refrigerant pressure P2, the process proceeds to the normal control in step ST8 and returns to step 1 again without performing high-pressure equivalent control. On the other hand, when the high-pressure refrigerant pressure P1 is higher than the high-pressure refrigerant pressure P2, the process proceeds to step ST2.

[0052] In step ST2, the refrigerant outlet liquid temperature T1 detected by the refrigerant outlet liquid temperature sensor (9) of the main refrigerant circuit (lb) is higher than a predetermined value X2 (for example, X2 = 0 ° C). Alternatively, it is determined whether or not the suction refrigerant pressure PS detected by the second low-pressure refrigerant pressure sensor (28) of the supercooling circuit (la) is higher than a predetermined value X3 (for example, X3 = 0.15 MPa). Here, the supercooling heat exchanger (8) has a supercooling capacity that is not increased so that the supercooling heat exchanger (8) and the second variable capacity compressor (20) do not malfunction. I have to. That is, the refrigerant outlet liquid When the temperature Tl is the predetermined value X2 = 0 ° C or less, or the low-pressure refrigerant pressure value PS is the predetermined value X3 = 0.15 MPa or less, the subcooling heat exchanger (8) may cause freezing puncture in the former. In the latter case, it is determined that the compression ratio of the second variable capacity compressor (20) may increase and the discharged refrigerant temperature may excessively increase, and the process proceeds to step ST3. On the other hand, when the refrigerant outlet liquid temperature T1 is higher than the predetermined value X2 = 0 ° C or the low pressure refrigerant pressure value P3 is higher than the predetermined value X3 = 0.15 MPa, the supercooling heat exchanger (8) It is determined that there is no possibility that the temperature of the refrigerant discharged from the freezing puncture or the second variable capacity compressor (20) will rise excessively, and the routine goes to Step ST4.

[0053] In step ST3, the frequency of the second variable capacity compressor (20) decreases. As a result, the supercooling capacity of the supercooling heat exchanger (8) decreases, so that the refrigerant outlet liquid temperature T1 and the low pressure refrigerant pressure P3 rise, and the freezing puncture of the supercooling heat exchanger (8) occurs. While the excessive increase in the refrigerant temperature discharged from the second variable capacity compressor (20) is avoided, the high-pressure refrigerant pressure PS in the supercooling circuit (la) is lowered, and the process proceeds to step ST5.

[0054] In step ST4, the frequency of the second variable capacity compressor (20) is increased. As a result, the supercooling capacity of the supercooling heat exchanger (8) increases, so that the refrigerant outlet liquid temperature T1 and the low pressure refrigerant pressure P3 drop while the high pressure refrigerant pressure of the supercooling circuit (la) is reduced. While PS increases, go to step ST5.

[0055] In step ST5, the evaporation temperature Te detected by the evaporation temperature sensor (11) provided in the main refrigerant circuit (lb) subtracts α (eg, α = 10) from the cooling set temperature X4 in the cooling target space. It is determined whether it is lower than the value. That is, it is determined whether or not the evaporation temperature Te is a temperature at which the cooling target space can be cooled to the cooling set temperature X4. Specifically, if the evaporation temperature Te is lower than the value obtained by subtracting the cooling set temperature X4, the process proceeds to step ST7, and if not lower, the process proceeds to step ST6.

[0056] In step ST6, the frequency of the first variable capacity compressor (2) is increased. As a result, the cooling capacity of the indoor heat exchanger (12) is increased, so that the evaporation temperature Te is lowered, while the high-pressure refrigerant pressure P1 of the main refrigerant circuit (lb) is increased, while the step is repeated. Return to ST 1.

[0057] In step ST7, the frequency of the first variable capacity compressor (2) decreases. This Thus, the cooling capacity of the indoor heat exchanger (12) is reduced, so that the evaporation temperature Te is increased while the high-pressure refrigerant pressure P1 of the main refrigerant circuit (lb) is decreased, but the process returns to step ST1. Return.

[0058] The high-pressure equivalent control operation is performed by repeating the above operation.

[0059] Effect of One Embodiment

According to this embodiment, the refrigeration apparatus performs the high-pressure equivalent control operation until the high-pressure refrigerant pressure in the supercooling circuit (la) approaches the high-pressure refrigerant pressure in the main refrigerant circuit (lb). The second compressor (20) in the supercooling circuit (la) can be actively operated. As a result, even if the main refrigerant circuit (lb) is not overloaded, the second compressor (20) of the supercooling circuit (la) can be operated. As a result, the cooling load of the refrigeration apparatus can be reduced. It can be shared by the main refrigerant circuit (lb) and the supercooling circuit (la).

In the present embodiment, the coefficient of performance of the refrigeration apparatus can be improved by sharing the cooling load of the refrigeration apparatus between the main refrigerant circuit (lb) and the subcooling circuit (la). Here, the reason why the coefficient of performance is improved will be described with reference to FIG. 3 showing the refrigeration cycle simulation results of the main refrigerant circuit (lb) and the supercooling circuit (la) of the present embodiment.

[0061] In the refrigeration cycle simulation, the evaporation temperature in the indoor heat exchanger (12) of the main refrigerant circuit (lb) is -40 ° C, and the supercooling heat exchanger (8) of the supercooling circuit (la) is The evaporating temperature is 0 ° C, the cooling capacity of the refrigeration system is constant at 25.2 Kw, and the condensation temperature of the main refrigerant circuit (lb) and subcooling circuit (la) is changed. The effect of coefficient of performance due to changes was investigated.

[0062] In Fig. 3, A is the case where the cooling operation of the refrigeration apparatus is performed only in the main refrigerant circuit (lb), and B and C are the cases where the main refrigerant circuit (lb) and the supercooling circuit (la) are performed. It is. A is the condensation temperature of the main refrigerant circuit (lb) is 50 ° C, B is the condensation temperature of the main refrigerant circuit (lb) and the subcooling circuit (la) is 47 ° C and 42 ° C, respectively. The condensation temperature of the refrigerant circuit (lb) and supercooling circuit (la) is 45 ° C.

[0063] When comparing the coefficient of performance of the refrigeration unit for each of A, B, and C, B and C have a larger coefficient of performance than A. This is a cooling operation only with the main refrigerant circuit (lb). This shows that the coefficient of performance is larger when the cooling operation is performed in the main refrigerant circuit (lb) and the subcooling circuit (la). In addition, when comparing B and C, the coefficient of performance is higher for C. This indicates that the coefficient of performance is larger when the condensing temperatures of the main refrigerant circuit (lb) and the subcooling circuit (la) are set to the same value. Furthermore, when the coefficient of performance of the main refrigerant circuit (lb) and the subcooling circuit (la) is compared for each of AB and C, the coefficient of performance of the subcooling circuit (la) exceeds all.

[0064] From the above, the cooling operation is not performed only with the main refrigerant circuit (lb) having a small coefficient of performance. The high-pressure equivalent control operation is performed with the main refrigerant circuit (lb) and the supercooling circuit (la) having a large coefficient of performance. The performance coefficient of the refrigeration apparatus can be improved by doing so.

[0065] << Other Embodiments >>

About the said embodiment, it is good also as the following structures.

[0066] For example, the main refrigerant circuit (lb) may be a refrigerant circuit that performs a two-stage compression refrigeration cycle, and a plurality of the indoor heat exchangers (12) are installed in parallel. Moyore.

[0067] Further, the supercooling heat exchanger (8) may be a double pipe type or a shell and tube type heat exchanger that does not need to be a plate type heat exchanger.

[0068] The above embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Industrial applicability

[0069] As described above, the present invention relates to a refrigeration apparatus including a supercooling circuit, and is particularly useful for a capacity control technique for the supercooling circuit.

Claims

The scope of the claims

[1] Variable capacity first compressor (2), first condenser (6), supercooling heat exchanger (8), first expansion mechanism (10) and first evaporator (12) connected in sequence The main refrigerant circuit (lb) that performs the refrigeration cycle, the second compressor (20), the second condenser (24), the second expansion mechanism (26), and the supercooling heat exchanger (8) are sequentially arranged. A refrigeration apparatus comprising a supercooling circuit (la) connected to perform a refrigeration cycle, and first capacity adjusting means capable of adjusting the capacity of the first compressor (2),

The second compressor (20) comprises a variable capacity compressor (20),

First high-pressure refrigerant pressure detection means (5) for detecting the high-pressure refrigerant pressure in the main refrigerant circuit (lb), and second high-pressure refrigerant pressure detection means (2 3) for detecting the high-pressure refrigerant pressure in the supercooling circuit (la). ) And second capacity adjusting means capable of adjusting the capacity of the second compressor (20), and controlling the first capacity adjusting means and the second capacity adjusting means to control the main refrigerant circuit ( 1) A refrigeration apparatus comprising high-pressure equivalent control means (32) for bringing the high-pressure refrigerant pressure value of b) close to the high-pressure refrigerant pressure value of the supercooling circuit (la).

[2] In claim 1,

An outlet liquid temperature detecting means (9) for detecting the refrigerant outlet liquid temperature on the main refrigerant circuit (lb) side of the supercooling heat exchanger (8),

If the refrigerant outlet liquid temperature is higher than a predetermined value, the high-pressure equivalent control means (32) controls the second capacity adjusting means to increase the capacity of the second compressor (20), and from the predetermined value A refrigeration apparatus comprising a first control unit that controls the second capacity adjusting means to reduce the capacity of the second compressor (20) if it is low.

[3] In claim 1,

Provided is an intake refrigerant pressure detection means (28) for detecting the intake refrigerant pressure of the second compressor (20) .The high pressure equivalent control means (32) is configured to provide the second capacity if the intake refrigerant pressure is higher than a predetermined value. The capacity of the second compressor (20) is increased by controlling the adjusting means, and if it is lower than a predetermined value, the capacity of the second compressor (20) is decreased by controlling the second capacity adjusting means. A refrigeration apparatus comprising a second control unit.

[4] In claim 1, Evaporation temperature detection means (11) for detecting the evaporation temperature of the main refrigerant circuit (lb) is provided, and the high pressure equivalent control means (32) is configured to adjust the first capacity adjustment means if the evaporation temperature is lower than a predetermined value. To control the first capacity adjusting means to increase the capacity of the first compressor (2) if the capacity of the first compressor (2) is higher than a predetermined value. A refrigeration apparatus comprising a portion.