JP4096984B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus provided with a supercooling circuit, and more particularly to a technology for controlling the capacity of the supercooling circuit.

  2. Description of the Related Art Conventionally, a refrigeration apparatus including a refrigerant circuit that performs a vapor compression refrigeration cycle is known. Among these refrigeration apparatuses, there is one in which 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.

  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 refrigerant piping. 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. Thus, 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 of the supercooling circuit are heat-exchanged to supercool the high-pressure liquid refrigerant. In addition, the degree of supercooling of the high-pressure liquid refrigerant can be increased. And the cooling capacity of the main refrigerant circuit can be increased by increasing the degree of supercooling of the high-pressure liquid refrigerant. Patent document 1 is mentioned as a prior art for controlling this supercooling circuit in the refrigeration apparatus provided with such a supercooling circuit.

  In the refrigeration apparatus of Patent Document 1, the first compressor of the main refrigerant circuit is configured with a variable capacity compressor, and based on the operating capacity of the first compressor and the low-pressure refrigerant pressure of the main refrigerant circuit, The start / stop control of the second compressor of the supercooling circuit is performed. Specifically, when the capacity of the variable capacity compressor is greater than or equal to a first predetermined value and the low-pressure refrigerant pressure is greater than or equal to a predetermined value, that is, when the main refrigerant circuit is in a cooling overload state, The second compressor of the circuit is activated. 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.

That is, the start / stop control is such that when the main refrigerant circuit is in a cooling overload state, the second compressor of the supercooling circuit is started, and when the main refrigerant circuit is not in the cooling overload state, the second compressor is stopped. It is configured.
Japanese Patent No. 3376844

  However, in the refrigeration apparatus of Patent Document 1, although the overload state of the main refrigerant circuit can be avoided by using the supercooling circuit, the supercooling circuit is activated if the main refrigerant circuit is not overloaded. do not do. In other words, 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, when the operation of the refrigeration system is such that the main refrigerant circuit is at a higher pressure than the normal pressure due to an increase in the outside air temperature, the input to the variable capacity compressor of the main refrigerant circuit becomes excessive, and the coefficient of performance decreases. Even in the operation, the second compressor of the supercooling circuit of the refrigeration apparatus in Patent Document 1 does not start when the low-pressure refrigerant pressure of the main refrigerant circuit is maintained.

  The present invention has been made in view of such points, and an object of the present invention is to provide a refrigeration apparatus having a supercooling circuit for increasing the cooling capacity, even if the refrigeration apparatus is not in an overload state. By actively operating the compressor of the circuit, the coefficient of performance of the refrigeration apparatus is improved.

The first invention is
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 order and refrigerated. The main refrigerant circuit (1b) that performs the cycle, the second compressor (20), the second condenser (24), the second expansion mechanism (26), and the supercooling heat exchanger (8) are connected in order. A refrigeration apparatus including a supercooling circuit (1a) for performing a refrigeration cycle and first capacity adjusting means capable of adjusting the capacity of the first compressor (2) is assumed.

The second compressor (20) is a variable capacity compressor (20), and includes a first high-pressure refrigerant pressure detection means (5) for detecting a high-pressure refrigerant pressure in the main refrigerant circuit (1b), and the excess compressor. A second high pressure refrigerant pressure detecting means (23) for detecting the high pressure refrigerant pressure of the cooling circuit (1a); and a second capacity adjusting means capable of adjusting a capacity of the second compressor (20), High pressure equivalent control means for controlling the high pressure refrigerant pressure value of the main refrigerant circuit (1b) and the high pressure refrigerant pressure value of the supercooling circuit (1a) by controlling the capacity adjusting means and the second capacity adjusting means. (32) .

The refrigeration apparatus of the first invention further comprises outlet liquid temperature detecting means (9) for detecting the refrigerant outlet liquid temperature on the main refrigerant circuit (1b) side of the supercooling heat exchanger (8), and the high pressure equivalent The control means (32) controls the second capacity adjusting means to increase the capacity of the second compressor (20) if the refrigerant outlet liquid temperature is higher than a predetermined value, and if lower than the predetermined value, the control means (32) A first control unit that controls the second capacity adjusting means to reduce the capacity of the second compressor (20) is provided.

In the first invention, for example, 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 (1a) as a target value. Using the high-pressure refrigerant pressure of the main refrigerant circuit (1b) as a target value, the high-pressure equivalent control means (32) can increase the capacity of the second compressor (20). Thereby, the high-pressure refrigerant pressure values of the main refrigerant circuit (1b) and the supercooling circuit (1a) can be made closer.

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

In the first invention, not only the high-pressure refrigerant pressure value of the main refrigerant circuit (1b) but also the set value at the refrigerant outlet liquid temperature of the main refrigerant circuit (1b) is set as a target value, and the high-pressure equivalent control means ( The first control unit 32) can control the capacity of the second compressor (20).

According to a second aspect of the present invention, in the first aspect of the invention, there is provided an intake refrigerant pressure detecting means (28) for detecting an intake refrigerant pressure of the second compressor (20), wherein the high pressure equivalent control means (32) If the refrigerant pressure is higher than a predetermined value, the second capacity adjusting means is controlled to increase the capacity of the second compressor (20). If the refrigerant pressure is lower than the predetermined value, the second capacity adjusting means is controlled to control the second capacity adjusting means. A second control unit for reducing the capacity of the second compressor (20) is provided.

In the second invention, not only the high pressure refrigerant pressure value of the main refrigerant circuit (1b) and the set value of the refrigerant outlet liquid temperature of the main refrigerant circuit (1b), but also the suction refrigerant pressure of the second compressor (20). The second control unit of the high-pressure equivalent control means (32) can control the capacity of the second compressor (20) with the set value at as a target value.

According to a third invention, in the first or second invention, there is provided an evaporation temperature detecting means (11) for detecting an evaporation temperature of the main refrigerant circuit (1b), and the high pressure equivalent control means (32) If the temperature is lower than a predetermined value, the first capacity adjusting means is controlled to reduce the capacity of the first compressor (2). If the temperature is higher than the predetermined value, the first capacity adjusting means is controlled to control the first capacity adjusting means. It is characterized by having a third control unit that increases the capacity of one compressor (2).

In the third aspect of the invention, not only the high-pressure refrigerant pressure value of the supercooling circuit (1a) but also the set value at the evaporation temperature of the main refrigerant circuit (1b) is set as the target value, and the high-pressure equivalent control means (32) The three control units can control the capacity of the first compressor (2).

  According to the present invention, by performing the high-pressure equivalent control, until the high-pressure refrigerant pressure of the supercooling circuit (1a) approaches the high-pressure refrigerant pressure of the main refrigerant circuit (1b), the supercooling circuit (1a) The second compressor (20) can be operated. Thereby, even if the main refrigerant circuit (1b) is not in an overload state, the second compressor (20) of the supercooling circuit (1a) can be operated. As a result, the cooling load of the refrigeration apparatus can be reduced. The main refrigerant circuit (1b) and the supercooling circuit (1a) can be shared. Here, regarding the sharing of the cooling load, the decrease in the cooling capacity of the main refrigerant circuit (1b) due to the decrease in the capacity of the first compressor (2) is the same as the cooling capacity due to the increase in the capacity of the second compressor (20). It becomes the composition which compensates with increase of.

  Further, the increase amount of the electric input due to the increase in the capacity of the second compressor (20) is smaller than the decrease amount of the electric input of the first compressor (2) due to the decrease in the cooling capacity of the main refrigerant circuit (1b). This is because the coefficient of performance of the supercooling circuit (1a) is larger than the coefficient of performance of the main refrigerant circuit (1b). Here, the reason why the coefficient of performance of the supercooling circuit (1a) is larger than that of the main refrigerant circuit (1b) is, for example, when the set temperature of the space to be cooled is −30 ° C., the evaporation saturation temperature of the main refrigerant circuit (1b) However, the evaporation saturation temperature of the supercooling circuit (1a) is around 0 ° C, and the low-pressure refrigerant pressure of the supercooling circuit (1a) 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 coefficient of performance of the supercooling circuit (1a) with a small high-low pressure difference is smaller than that of the main refrigerant circuit (1b) Because it becomes bigger.

  As described above, the cooling operation is not performed only by the main refrigerant circuit (1b) having a small coefficient of performance, but the cooling operation is shared by the main refrigerant circuit (1b) and the supercooling circuit (1a) having a large coefficient of performance. As a result, the total coefficient of performance of the refrigeration apparatus can be improved.

Further, according to the first aspect , during the high pressure equivalent control, the first control unit 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 of the supercooling circuit (1a) increases. This is because the supercooling capability 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 (1b) is also lowered. That is, if the upper Symbol pressure equivalent means increased capacity of the high pressure refrigerant pressure by the second compressor as a target value (20) of the main refrigerant circuit (1b), the refrigerant outlet fluid temperature by conditions It is possible that it falls too much than necessary. Therefore, in order to prevent the refrigerant outlet liquid temperature from dropping too much, the one control unit limits the increase in capacity of the second compressor (20).

Further, according to the second 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 of the supercooling circuit (1a) increases. 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 (1b) as a target value, as in the first invention, It is conceivable that the suction refrigerant pressure is too low. Therefore, in order to prevent the suction refrigerant pressure from dropping excessively, the two control units limit the increase in capacity of the second compressor (20).

According to the third aspect of the present invention, during the high pressure equivalent control, the third control unit of the high pressure equivalent control restricts a decrease in capacity in the first compressor (2) based on the evaporation temperature. be able to. 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 (1b) is reduced and the cooling capacity is reduced. This is because the target space is insufficiently cooled. That is, 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 (1a) as a target value, as in the first invention, It is conceivable that the evaporation temperature rises more than necessary. 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). Thereby, the high-pressure equivalent control means (32) can perform high-pressure equivalent control while maintaining the cooling capacity of the main refrigerant circuit (1b).

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

-Configuration of refrigeration equipment-
FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to this embodiment. This refrigeration apparatus is for cooling a space to be cooled (for example, a freezer compartment). The refrigeration apparatus includes a main refrigerant circuit (1b) 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 (1b). And a supercooling circuit (1a). The refrigeration apparatus is provided with a controller (high pressure equivalent control means) (32) for controlling the operation of the main refrigerant circuit (1b) and the supercooling circuit (1a).

<Main refrigerant circuit>
The main refrigerant circuit (1b) includes a first variable capacity compressor (first compressor) (2), a first outdoor heat exchanger (first condenser) (6), and the supercooling heat exchanger (8 ), A first expansion valve (first expansion mechanism) (10), and an indoor heat exchanger (first evaporator) (12) are sequentially connected by a refrigerant pipe to perform a vapor compression refrigeration cycle. ing.

  An inverter (not shown) is connected to the first variable capacity compressor (2). The inverter is configured to supply a current to the first variable displacement compressor (2) and to change the frequency of the current. 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, a first suction refrigerant pipe (15) is connected to the suction side of the first variable displacement compressor (2), and a 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).

  The first outdoor heat exchanger (6) is a cross-fin type fin-and-tube heat exchanger, and a first blower fan is located in the vicinity of the first outdoor heat exchanger (6). (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). .

  The said supercooling heat exchanger (8) is comprised with the plate fin type heat exchanger, and the 1st, 2nd flow path (8a, 8b) is formed in this plate fin type heat exchanger. . The refrigerant circulating through the main refrigerant circuit (1b) flows through the first flow path (8a), and the refrigerant circulating through the supercooling circuit (1a) flows through the second flow path (8b). And the refrigerant | coolant which flows through the said main refrigerant circuit (1b) side is cooled by this refrigerant | coolant exchanging heat. The 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) of the refrigerant flowing through the main refrigerant circuit (1b) side includes: The refrigerant pipe is connected to the supercooling heat exchanger (8) of the main refrigerant circuit (1b) and the first expansion valve (10).

  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.

  Similar to the first outdoor heat exchanger (6), the indoor heat exchanger (12) is a cross-fin fin-and-tube heat exchanger. Although not shown, the heat transfer tubes are arranged in a plurality of paths, and a large number of aluminum fins are installed orthogonal to the heat transfer tubes. 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 in the vicinity of 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).

  The main refrigerant circuit (1b) 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 supercooling heat exchanger. The other end is connected to the first high-pressure liquid refrigerant pipe (7) between the indoor heat exchanger (12) and the first variable capacity compressor (2). 1 It is connected to the 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).

<Supercooling circuit>
The supercooling circuit (1a) includes a second variable capacity compressor (20), a second outdoor heat exchanger (second condenser) (24), a second expansion valve (second expansion mechanism) (26), The supercooling heat exchanger (8) is connected to the refrigerant pipe in order to perform a vapor compression refrigeration cycle.

  Similarly to the first variable capacity compressor (2) of the main refrigerant circuit (1b), the second variable capacity compressor (20) is connected to an inverter (not shown). The capacity of the capacity type 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).

  The second outdoor heat exchanger (24) is constituted by a cross fin type fin-and-tube heat exchanger, similarly to the first outdoor heat exchanger (6) of the main refrigerant circuit (1b). A second blower fan (24a) and a second outside air temperature sensor (24b) are provided in the vicinity of the second outdoor heat exchanger (24). Although not shown, in the second outdoor heat exchanger (24), the heat transfer tubes are arranged in a plurality of paths, and a large number of aluminum fins are installed orthogonal 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).

  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).

  The supercooling heat exchanger (8) is constituted by a plate fin type heat exchanger as described above, and the second low-pressure refrigerant is provided in the second flow path (8b) in the plate fin type heat exchanger. Pipe (27) is connected.

<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. The high pressure equivalent control operation of the first variable capacity compressor (2) and the second variable capacity compressor (20) is performed in accordance with a detection signal from the second low pressure refrigerant pressure sensor (28). Yes.

-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 (1b) and the supercooling circuit (1a) will be described, and then the high-pressure equivalent control operation in the main refrigerant circuit (1b) and the supercooling circuit (1a) will be described.

<Cooling operation of main refrigerant circuit>
In the cooling operation of the main refrigerant circuit (1b), 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 degree of the 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.

  When the first variable capacity compressor (2) is started, high-pressure gas refrigerant is discharged from the discharge side of the first variable capacity compressor (2) through the first discharge refrigerant pipe (3). 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 a high-pressure liquid refrigerant. The refrigerant that has become the high-pressure liquid refrigerant flows out of the first outdoor heat exchanger (6) and is supercooled when passing through the first flow path (8a) of the supercooling heat exchanger (8). The supercooling heat exchanger (8) flows out.

  The supercooled high-pressure liquid refrigerant flows into the first expansion valve (10). The high-pressure liquid refrigerant flowing into the first expansion valve (10) is reduced in pressure when passing through the first expansion valve (10) to become a low-pressure liquid refrigerant, and flows into the indoor heat exchanger (12). The low-pressure liquid refrigerant flowing into the indoor heat exchanger (12) absorbs heat from the air in the cooling target space 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 to become 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.

  As described above, the refrigerant circulates in the main refrigerant circuit (1b) to cool the space to be cooled.

<Cooling operation of supercooling circuit>
In the cooling operation of the supercooling circuit (1a), 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 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.

  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). Flows 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). Heat is absorbed from the high-pressure liquid refrigerant in the main refrigerant circuit (1b). 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 flows into the second variable capacity compressor (20). The low pressure gas refrigerant that has flowed into the second variable capacity compressor (20) is compressed to become a 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 (1a) and the high-pressure liquid refrigerant in the main refrigerant circuit (1b) is cooled.

<High pressure equivalent control operation>
Next, the operation of high-pressure equivalent control in the main refrigerant circuit (1b) and the supercooling circuit (1a) will be described based on the control flow of FIG. Here, the high-pressure equivalent control means that the main refrigerant circuit (1b) and the subcooling circuit ((2)) are controlled 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 1a) and equalizes both high-pressure refrigerant pressures.

  When the cooling operation of the refrigeration apparatus is started, in step ST1, the outside air temperature Ta detected by the first outside air temperature sensor (6b) is larger than a predetermined value X1 (for example, X1 = 20 ° C.) and the first variable. When the frequency of the capacity type compressor (2) is 50% or more of the maximum frequency of the first variable capacity type compressor (2), or the frequency of the first variable capacity type compressor (2) is the first variable The high-pressure refrigerant pressure P1 detected by the first high-pressure refrigerant pressure sensor (5) of the main refrigerant circuit (1b) when the maximum frequency of the capacity type compressor (2) is 90% or more is the supercooling circuit (1a). ) Of the high pressure refrigerant pressure P2 detected by the second high pressure refrigerant pressure sensor (23). When the high-pressure refrigerant pressure P1 is equal to or lower than the high-pressure refrigerant pressure P2, the process proceeds to the normal control in step ST8 and returns to step 1 again without performing the 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.

  In step ST2, the refrigerant outlet liquid temperature T1 detected by the refrigerant outlet liquid temperature sensor (9) of the main refrigerant circuit (1b) is higher than a predetermined value X2 (for example, X2 = 0 ° C.), or the supercooling circuit. It is determined whether or not the suction refrigerant pressure PS detected by the second low-pressure refrigerant pressure sensor (28) of (1a) is higher than a predetermined value X3 (for example, X3 = 0.15 MPa). Here, the supercooling capacity of the supercooling heat exchanger (8) becomes too large so that the supercooling heat exchanger (8) and the second variable capacity compressor (20) do not malfunction. ing. That is, when the refrigerant outlet liquid temperature T1 is equal to or lower than the predetermined value X2 = 0 ° C. or the low-pressure refrigerant pressure value PS is equal to or lower than the predetermined value X3 = 0.15 MPa, the supercooling heat exchanger (8) is frozen punctured 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 risk that the refrigerant temperature discharged from the second variable capacity compressor (20) will rise excessively, and the routine goes to Step ST4.

  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 supercooling heat exchanger (8) While an 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 (1a) is lowered, and the process proceeds to step ST5.

  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 PS of the supercooling circuit (1a) decreases. While increasing, the process proceeds to step ST5.

  In step ST5, the evaporation temperature Te detected by the evaporation temperature sensor (11) provided in the main refrigerant circuit (1b) is less than the value obtained by subtracting α (for example, α = 10) from the cooling set temperature X4 in the cooling target space. Determine whether it is low. That is, it is determined whether or not the evaporation temperature Te is a temperature at which the space to be cooled can be cooled to the cooling set temperature X4. Specifically, if the evaporation temperature Te is lower than the value obtained by subtracting α from the cooling set temperature X4, the process proceeds to step ST7, and if not lower, the process proceeds to step ST6.

  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) increases, so that the evaporation temperature Te is lowered, while the high-pressure refrigerant pressure P1 of the main refrigerant circuit (1b) is increased, and the process returns to step ST1 again. .

  In step ST7, the frequency of the first variable capacity compressor (2) decreases. As a result, the cooling capacity of the indoor heat exchanger (12) decreases, so that the evaporation temperature Te increases, while the high-pressure refrigerant pressure P1 of the main refrigerant circuit (1b) decreases, and the process returns to step ST1 again. .

  The high pressure equivalent control operation is performed by repeating the above operation.

-Effect of the embodiment-
According to this embodiment, the refrigeration apparatus performs the high-pressure equivalent control operation, so that the high-pressure refrigerant pressure in the supercooling circuit (1a) approaches the high-pressure refrigerant pressure in the main refrigerant circuit (1b). The second compressor (20) of the cooling circuit (1a) can be actively operated. Thereby, even if the main refrigerant circuit (1b) is not in an overload state, the second compressor (20) of the supercooling circuit (1a) can be operated. As a result, the cooling load of the refrigeration apparatus can be reduced. The main refrigerant circuit (1b) and the supercooling circuit (1a) can be shared.

  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 (1b) and the subcooling circuit (1a). Here, the reason why the coefficient of performance is improved will be described based on FIG. 3 showing the refrigeration cycle simulation results of the main refrigerant circuit (1b) and the supercooling circuit (1a) of the present embodiment.

  In the refrigeration cycle simulation, the evaporation temperature in the indoor heat exchanger (12) of the main refrigerant circuit (1b) is −40 ° C., and the evaporation temperature in the supercooling heat exchanger (8) of the supercooling circuit (1a) is 0. ℃ and the cooling capacity of the above refrigeration equipment is fixed at 25.2Kw, changing the condensation temperature of the main refrigerant circuit (1b) and subcooling circuit (1a), and the effect of coefficient of performance due to the change of the condensation temperature Investigated about.

  A in FIG. 3 is the case where the cooling operation of the refrigeration apparatus is performed only by the main refrigerant circuit (1b), and B and C are the cases where the cooling operation is performed by the main refrigerant circuit (1b) and the supercooling circuit (1a). A is the condensation temperature of the main refrigerant circuit (1b) at 50 ° C., B is the condensation temperatures of the main refrigerant circuit (1b) and the subcooling circuit (1a) at 47 ° C. and 42 ° C., respectively, and C is the main refrigerant circuit (1b). ) And the condensation temperature of the supercooling circuit (1a) is 45 ° C.

  When comparing the coefficient of performance of the refrigeration system for each of A, B, and C, B and C have a larger coefficient of performance than A. This indicates that the coefficient of performance is larger in the cooling operation in the main refrigerant circuit (1b) and the subcooling circuit (1a) than in the cooling operation only in the main refrigerant circuit (1b). When comparing B and C, C has a higher coefficient of performance. This indicates that the coefficient of performance is larger when the condensation temperatures of the main refrigerant circuit (1b) and the subcooling circuit (1a) are set to the same value. Furthermore, when the coefficient of performance of the main refrigerant circuit (1b) and the supercooling circuit (1a) is compared for each of A, B, and C, the coefficient of performance of the supercooling circuit (1a) is higher in all cases.

  From the above, it is better to perform the high-pressure equivalent control operation with the main refrigerant circuit (1b) and the supercooling circuit (1a) with a large coefficient of performance rather than performing the cooling operation only with the main refrigerant circuit (1b) with a small coefficient of performance. The coefficient of performance of the refrigeration apparatus can be improved.

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

  For example, the main refrigerant circuit (1b) may be a refrigerant circuit that performs a two-stage compression refrigeration cycle, or a plurality of the indoor heat exchangers (12) may be installed in parallel.

  Further, the supercooling heat exchanger (8) does not have to be constituted by a plate heat exchanger, and may be constituted by a double pipe type or a shell and tube type heat exchanger.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  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.

It is a refrigerant circuit figure of the refrigerating device concerning an embodiment. It is a control flowchart of the freezing apparatus which concerns on embodiment. It is a table | surface which shows the relationship between the condensation temperature of a main refrigerant circuit and a supercooling circuit, and the coefficient of performance of a freezing apparatus.

Explanation of symbols

1 Refrigeration equipment
1a Supercooling circuit
1b 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 First expansion valve (first 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)

Claims (3)

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 order and refrigerated. The main refrigerant circuit (1b) that performs the cycle, the second compressor (20), the second condenser (24), the second expansion mechanism (26), and the supercooling heat exchanger (8) are connected in order. A refrigeration apparatus comprising a supercooling circuit (1a) for performing a refrigeration cycle, and first capacity adjusting means capable of adjusting the capacity of the first compressor (2),
The second compressor (20) is composed of a variable capacity compressor (20),
First high pressure refrigerant pressure detecting means (5) for detecting the high pressure refrigerant pressure of the main refrigerant circuit (1b), and second high pressure refrigerant pressure detecting means (23) for detecting the high pressure refrigerant pressure of the supercooling circuit (1a). And second capacity adjusting means capable of adjusting the capacity of the second compressor (20),
A high pressure for controlling the high pressure refrigerant pressure value of the main refrigerant circuit (1b) and the high pressure refrigerant pressure value of the supercooling circuit (1a) by controlling the first capacity adjusting means and the second capacity adjusting means. with an equivalent control means (32),
An outlet liquid temperature detecting means (9) for detecting a refrigerant outlet liquid temperature on the main refrigerant circuit (1b) 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 lowers it below the predetermined value. For example, a refrigeration apparatus comprising a first control unit that controls the second capacity adjusting means to reduce the capacity of the second compressor (20) . In claim 1,
An intake refrigerant pressure detecting means (28) for detecting an intake refrigerant pressure of the second compressor (20);
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 lower than the predetermined value. A refrigeration apparatus comprising a second control unit that controls the second capacity adjusting means to reduce the capacity of the second compressor (20) . In claim 1 or 2,
Evaporation temperature detection means (11) for detecting the evaporation temperature of the main refrigerant circuit (1b),
The high-pressure equivalent control means (32) controls the first capacity adjusting means to reduce the capacity of the first compressor (2) if the evaporation temperature is lower than a predetermined value, and if higher than the predetermined value, A refrigeration apparatus comprising a third control unit for controlling the first capacity adjusting means to increase the capacity of the first compressor (2) .

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