JP2014088974A - Refrigerator and refrigeration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerator and the like capable of improving energy-saving performance while securing high reliability.SOLUTION: A refrigerator includes: at least a low stage-side compressor 1 compressing a refrigerant and discharging the same; an auxiliary radiator 2 for allowing the refrigerant discharged by the low stage-side compressor 1 to exchange heat with ambient air so that the refrigerant radiates heat; a high stage-side compressor 3 compressing the refrigerant radiating heat in the auxiliary radiator 2 and discharging the same; and a high stage-side radiator 4 for allowing the refrigerant discharged by the high stage-side compressor 3 to exchange heat with the ambient air so that the refrigerant radiates heat. The high stage-side radiator 4 and the auxiliary radiator 2 are constituted on the basis of a prescribed radiation amount ratio as a ratio of a radiation amount of the refrigerant in the auxiliary radiator 2 to the total radiation amount of a radiation amount to make the refrigerant radiate heat to achieve a saturated gas state in the auxiliary radiator 2 and a radiation amount of the refrigerant in the high stage-side radiator 4 when a temperature of the ambient air is a prescribed low ambient temperature.

Description

  The present invention relates to a refrigerator and the like. In particular, the present invention relates to the construction of a refrigerant circuit using an auxiliary radiator in a two-stage refrigeration cycle.

  For example, in a refrigeration system using a refrigeration cycle (heat pump cycle), a compressor, a radiator (condenser), a throttle device (decompression device), and a cooler (evaporator) are basically connected by a refrigerant pipe. The refrigerant circuit which circulates is constituted.

  In a refrigeration apparatus, there is a two-stage cycle refrigeration apparatus that performs a refrigerant compression process divided into two stages, a low-stage side and a high-stage side, in order to perform cooling in a low temperature range of minus several tens of degrees. In such a two-stage cycle refrigeration apparatus, for example, an apparatus in which an auxiliary radiator is installed in front of a high-stage compressor has been proposed. The refrigerant discharged from the low-stage compressor is radiated by an auxiliary radiator, cooled, and sucked into the high-stage compressor, thereby improving the operation efficiency (see, for example, Patent Document 1). .

Japanese Patent No. 4219198

  In the refrigeration apparatus described in Patent Document 1, it is said that the operation efficiency can be improved by an auxiliary radiator that cools the refrigerant discharged from the low-stage compressor. However, in such a refrigeration apparatus, there is a possibility that the refrigerant may condense in the auxiliary radiator depending on the outside air temperature, the operating condition of the compressor, and the like. If the high-stage compressor sucks the liquid refrigerant (liquid refrigerant) formed by the condensation, there is a possibility that the liquid refrigerant may be damaged.

  In Japanese Patent Laid-Open No. 2004-228688, the compressor is prevented from being damaged by preventing the refrigerant from condensing in the auxiliary radiator by increasing the rotational speed of the compressor. However, when the rotational speed of the compressor is increased, the cooling capacity increases, so that the balance between the cooling load and the cooling capacity is lost, and the object to be cooled may be overcooled. Moreover, energy saving property may fall because the frequency of starting and stopping of the refrigeration apparatus increases.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a refrigerator or the like that can achieve energy saving while ensuring high reliability.

  The refrigerator according to the present invention includes a low-stage compressor that compresses and discharges a refrigerant, an auxiliary radiator that radiates the refrigerant by heat-exchange between the refrigerant discharged from the low-stage compressor and ambient air, and an auxiliary At least a high-stage compressor that compresses and discharges the refrigerant radiated by the radiator, and a high-stage radiator that radiates the refrigerant by exchanging heat between the refrigerant discharged from the high-stage compressor and the ambient air. When the ambient air temperature is a predetermined low ambient temperature, the amount of heat released from the auxiliary radiator to radiate the refrigerant to the saturated gas state and the total amount of heat released from the refrigerant in the high-stage radiator The high-stage heat radiator and the auxiliary heat radiator are configured based on a predetermined heat radiation amount ratio that is a ratio of the heat radiation amount of the refrigerant in the auxiliary heat radiator.

  The present invention is based on a predetermined heat release amount ratio between a heat release amount for radiating the refrigerant to the saturated gas state by the auxiliary radiator and a heat release amount of the refrigerant in the high stage side radiator at a predetermined low ambient temperature. Since the side radiator and auxiliary radiator are configured, a radiator that supports liquid compression of the high stage compressor that occurs when the ambient temperature is low is configured, and liquid compression of the high stage compressor is performed throughout the year. This makes it possible to obtain high reliability and energy saving.

It is a figure which shows the structure of the freezing apparatus which concerns on Embodiment 1 of this invention. It is the schematic which shows the structure of the integrated radiator 7 of the refrigeration apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between enthalpy and pressure in a freezing apparatus. It is a figure which shows the relationship between an intermediate pressure and a compressor input. It is the figure explaining the heat dissipation in the case where the low stage side condensing temperature is lower than the outside air temperature and when it is higher with the Mollier diagram. It is a figure for demonstrating the relationship between the heat dissipation of the auxiliary radiator 2, and COP. It is a figure for demonstrating the heat dissipation of the integrated radiator 7 of the refrigeration apparatus which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the heat dissipation rate of the auxiliary radiator in the integrated radiator of the refrigeration apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the thermal radiation amount ratio of the auxiliary radiator 2 for every refrigerant | coolant. It is a figure for demonstrating sufficient heat processing capability with respect to the thermal radiation amount which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the freezing apparatus which concerns on Embodiment 2 of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a refrigeration apparatus including a refrigerator according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a refrigeration apparatus according to Embodiment 1 of the present invention. In FIG. 1, a low-stage compressor 1, an auxiliary radiator 2, a high-stage compressor 3, a high-stage radiator 4, an expansion valve 5 as a pressure reducing device, and an evaporator 6 that functions as a cooler are sequentially connected. Thus, a refrigerant circuit is configured. In the present embodiment, the refrigerator 11 includes the low-stage compressor 1, the auxiliary radiator 2, the high-stage compressor 3, the high-stage radiator 4 and the expansion valve 5, and the evaporator 6 is a load. The indoor unit 12 which becomes an apparatus has. Here, the expansion valve 5 may be included in the indoor unit 12.

  The low-stage compressor 1 compresses and discharges the refrigerant from the suction side pipe side. The auxiliary radiator 2 exchanges heat between the refrigerant discharged from the low-stage compressor 1 and the ambient air (outside air), and radiates the refrigerant. The high stage compressor 3 compresses and discharges the refrigerant radiated by the auxiliary radiator 2. The high stage side radiator 4 exchanges heat between the refrigerant discharged from the high stage side compressor 3 and the ambient air, and radiates (condenses) the refrigerant. The expansion valve 5 depressurizes the refrigerant radiated by the high stage side radiator 4. The evaporator 6 evaporates the refrigerant decompressed by the expansion valve 5.

  Here, the high-stage radiator 4 and the auxiliary radiator 2 constitute an integrated radiator 7. A radiator fan 8 is provided in the vicinity of the integrated radiator 7. The radiator fan 8 allows the outside air to pass through the integrated radiator 7, exchanges heat with the refrigerant passing through the heat transfer tube of the integrated radiator 7, and then exhausts the outside air after the heat exchange to the outside of the integrated radiator 7. Let

  FIG. 2 is a schematic diagram showing the configuration of the integrated radiator 7 of the refrigeration apparatus according to Embodiment 1 of the present invention. In FIG. 2, the integrated radiator 7 is a plate fin tube type heat exchanger configured by passing a heat transfer tube 72 through a flat plate heat transfer fin 71. Here, in the present embodiment, the high-stage radiator 4 and the auxiliary radiator 2 are integrated by sharing the heat transfer fins 71, but the heat transfer fins 71 are divided and configured. May be. Due to the integration, the manufacture of the heat exchanger is facilitated. On the other hand, if the heat transfer fins 71 are divided between the auxiliary radiator 2 and the high-stage side radiator 4 that are at a high temperature, the thermal insulation effect is increased, and thus the auxiliary radiator 2 and the high-stage side heat dissipation. Both units 4 can dissipate heat more efficiently.

  Further, in the integrated radiator 7, as shown in FIG. 2, the auxiliary radiator 2 for cooling the high-temperature gaseous refrigerant (gas refrigerant) discharged from the low-stage compressor 1 is provided above the heat exchanger. The upper stage radiator 4 is arranged in the lower part (lower side in the gravity direction). Thereby, the heat radiation of the auxiliary radiator 2 does not interfere with the high-stage radiator 4 side. Therefore, the heat transfer fluid heated by the auxiliary radiator 2 does not move to the high stage radiator 4 side, and both the auxiliary radiator 2 and the high stage radiator 4 can efficiently radiate heat.

  In the present embodiment, as shown in FIG. 2, the radiation of the auxiliary radiator 2 with respect to the total radiation amount of the integrated radiator 7 (the radiation amount of the high-stage radiator 4 + the radiation amount of the auxiliary radiator 2). The apparatus is characterized in that the heat dissipation ratio is within a range equal to or less than the heat dissipation ratio at a predetermined low ambient temperature and the integrated radiator 7 (the high-stage radiator 4 and the auxiliary radiator 2) is configured. . Details will be described later.

In the present embodiment, the refrigerant used for the refrigeration apparatus configured as described above is carbon dioxide (CO ₂ ). For example, as the indoor unit 12 to be connected to the refrigerator 11 of the present embodiment, for example, in a supermarket showcase or the like, piping or the like may be opened due to rearrangement or the like, and refrigerant leakage may occur. There is. Therefore, considering refrigerant leakage, it is desirable to use CO ₂ having a small influence on global warming as the refrigerant.

Further, the refrigeration apparatus of the present embodiment can also be applied to a showcase with a built-in refrigerator. The showcase with a built-in refrigerator has a small amount of refrigerant leakage because the refrigerant circuit is not opened. For this reason, it may be a conventionally used HFC refrigerant having a high global warming potential, but is essentially a refrigerant having a small influence on global warming, such as HFO refrigerant, HC refrigerant, CO ₂ , ammonia, Water is desirable.

The operation of the refrigeration apparatus configured as described above will be described based on the refrigerant flow.
The low stage compressor 1 compresses the CO ₂ refrigerant. The compressed and discharged CO ₂ refrigerant is cooled by radiating heat with the auxiliary radiator 2 in the integrated radiator 7 and then sucked into the high-stage compressor 3. The high stage side compressor 3 further compresses the CO ₂ refrigerant. The CO ₂ refrigerant compressed and discharged by the high-stage compressor 3 is condensed by radiating heat from the high-stage radiator 4 in the integrated radiator 7 and then depressurized by the expansion valve 5 to be evaporated. 6 flows in. The CO ₂ refrigerant that has flowed into the evaporator 6 evaporates and returns to the low-stage compressor 1. The load is cooled when the CO ₂ refrigerant evaporates in the evaporator 6.

  In the refrigeration apparatus of the present embodiment, the low-stage high pressure (intermediate pressure) is adjusted by the capacity ratio between the low-stage compressor 1 and the high-stage compressor 3. Here, in the present embodiment, the low-stage-side high-pressure can be adjusted by adopting a variable operating capacity type that can control the rotation speed of the motor that drives the compressor. The low-stage high pressure may be adjusted according to the excluded volume ratio of the high-stage compressor 3.

  FIG. 3 is a diagram illustrating a relationship between enthalpy and pressure in the refrigeration apparatus. In the refrigeration apparatus of the present embodiment, the cooling load changes according to the outside air temperature, the refrigeration capacity (heat exchange amount of the evaporator 6) is determined for the cooling load, and the determined refrigeration capacity is kept constant. The refrigerant flow rate is controlled by the low-stage compressor 1 so as to keep it. For this reason, even if the driving speed of the high stage compressor 3 is increased from a certain operating state to increase the capacity of the high stage compressor 3, the driving speed of the low stage compressor 1 does not follow. . Therefore, when the capacity of the high-stage compressor 3 increases, the high-stage suction pressure decreases, and the low-stage high pressure (low-stage discharge pressure) also decreases. Conversely, if the capacity of the high-stage compressor 3 is reduced, the low-stage high pressure increases.

  As is apparent from FIG. 3, when the driving speed of the high-stage compressor 3 is increased and the low-stage high pressure is decreased, the input (electric power) of the high-stage compressor 3 is increased (WH1 <WH2). On the other hand, the input of the low-stage compressor 1 is small (WL1> WL2).

  By the way, when the compression ratios of the low-stage compressor 1 and the high-stage compressor 3 are substantially equal, the total input (input of the high-stage compressor 3 + input of the low-stage compressor 1) is minimized. The operating efficiency of the entire two-stage cycle is optimal. Therefore, the capacity of the high-stage compressor 3 is adjusted, and the low-stage high pressure is adjusted so that the compression ratio between the low-stage compressor 1 and the high-stage compressor 3 is substantially equal. Therefore, the low stage side high pressure is not supercritical. For this reason, the saturation temperature at which the phase change occurs due to the pressure is determined.

  FIG. 4 is a diagram showing the relationship between the intermediate pressure and the input of the compressor. FIG. 4 is a summary of the above-described relationship, where the horizontal axis is the low-stage high pressure (intermediate pressure) and the vertical axis is the input in the two-stage cycle refrigeration system, and the input (enthalpy difference) of the high-stage compressor 3. ) And the input (enthalpy difference) of the low-stage compressor 1 and their total inputs. As shown in FIG. 4, it can be seen that the total input becomes the smallest when the compressor inputs in the high-stage compressor 3 and the low-stage compressor 1 are substantially the same. At this time, COP (= refrigeration capacity / (high stage side compressor input + low stage side compressor input)) is maximized.

  From the above, the capacity control of the high-stage compressor 3 is controlled with the target of the low-stage high pressure (hereinafter referred to as the optimum intermediate pressure) in which the compression ratio between the high-stage compressor 3 and the low-stage compressor 1 is substantially the same. Do. Thereby, the effect that the COP of the two-stage cycle refrigeration apparatus is maximized can be obtained. Here, in the present embodiment, a case where the capacity control of the high-stage compressor 3 is performed will be described. However, the present invention is not limited thereto, and the compression ratio of the low-stage compressor 1 and the high-stage compressor 3 are not limited thereto. What is necessary is just to adjust the capacity | capacitance ratio of the capacity | capacitance of the low stage side compressor 1 and the capacity | capacitance of the high stage side compressor 3 so that the compression ratio of this may become equivalent.

  The high stage side high pressure varies depending on the temperature of the ambient air related to heat exchange with the refrigerant in the high stage side radiator 4. In the present embodiment, the high-stage radiator 4 is housed in a refrigerator 11 installed outdoors. For this reason, it is the outside air that exchanges heat with the refrigerant in the high-stage radiator 4. For example, if the outside air temperature rises, the high stage side high pressure rises and the optimum intermediate pressure also rises. On the other hand, if the outside air temperature decreases, the optimum intermediate pressure similarly decreases. Thus, the optimum intermediate pressure changes with the outside air temperature.

  Here, in this embodiment, in order to maintain the pressure operation range of the compressor, the rotational speed of the radiator fan 8 is controlled to adjust the high stage side high pressure. At this time, as in the present embodiment, the capacity control of the high-stage compressor 3 is performed with the target of the optimum intermediate pressure that makes the compression ratios of the high-stage compressor 3 and the low-stage compressor 1 substantially the same. Then, the saturation temperature of the refrigerant at the optimum intermediate pressure may be higher than the outside air temperature.

<Difference in heat dissipation of auxiliary radiator 2 when low-stage side condensation temperature is lower and higher than outside temperature>
Next, the heat radiation amount of the auxiliary radiator 2 will be considered. In the refrigeration apparatus of the present embodiment, since the pressure control as described above is performed, there are cases where the saturation temperature of the optimum intermediate pressure becomes lower than the outside air temperature (ambient temperature) and becomes higher (including the same case). is there. Since the auxiliary radiator 2 is a radiator that radiates the heat of the refrigerant to the outside air, the refrigerant discharged from the low-stage compressor 1 can exchange heat with the outside air at the auxiliary radiator 2 only to the maximum outside temperature. It does not fall. Also, when the low-stage side condensation temperature is lower than the outside air temperature and when it is higher than the outside air temperature, the amount of heat released differs even when the auxiliary radiator 2 lowers the refrigerant at the discharge temperature to the same outside air temperature.

  FIG. 5 is a diagram illustrating the amount of heat released when the condensation temperature is lower and higher than the outside air temperature with the Mollier diagram. FIG. 5A shows the heat dissipation enthalpy difference when the condensation temperature is higher than the outside air temperature, and FIG. 5B shows the heat dissipation enthalpy difference when the condensation temperature is lower than the outside air temperature.

(A) When the condensation temperature is higher than the outside air temperature Consider the case where the temperature of the refrigerant discharged from the compressor (the temperature at point a) is, for example, 80 ° C. to 90 ° C., the outside air temperature is 20 ° C., and the condensation temperature is 25 ° C. .
Since the radiator is a radiator that radiates the heat of the refrigerant to the outside air, as shown in FIG. 5A, the refrigerant at 80 ° C. to 90 ° C. (point a) is exchanged with the outside air by the radiator. First, it lowers to 25 ° C. (point b) which is the condensation temperature in the gas state. And it is condensed and liquid state is maintained while maintaining 25 ° C. (point c). Since the outside air temperature is 20 ° C., the refrigerant can further dissipate heat and falls to 20 ° C. (point d) in a liquid state. In this way, when the condensation temperature is higher than the outside air temperature, the refrigerant condenses, so that cooling accompanied with a phase change is performed.

(B) When the condensing temperature is lower than the outside air temperature The temperature of the refrigerant discharged from the low-stage compressor 1 (the temperature at point a) is, for example, 80 ° C to 90 ° C, the outside air temperature is 20 ° C, and the condensing temperature is 10 ° C. Think about the case. Since the auxiliary radiator 2 is a radiator that radiates the heat of the refrigerant to the outside air, as described above, the refrigerant at 80 ° C. to 90 ° C. has a maximum outside air temperature of 20 ° C. due to heat exchange with the outside air in the auxiliary radiator 2. It will only go down. Therefore, as shown in FIG. 5B, the refrigerant (point a) at 80 ° C. to 90 ° C. becomes 20 ° C. (point b) while being in a gas state in the auxiliary radiator 2. For this reason, when the condensation temperature is lower than the outside air temperature, the auxiliary radiator 2 cannot perform the cooling accompanied by the phase change due to the condensation, and performs the cooling in the gaseous state.

<Relationship between heat dissipation of auxiliary radiator 2 and COP>
FIG. 6 is a diagram for explaining the relationship between the heat dissipation amount of the auxiliary radiator 2 and the COP. FIG. 6 shows a Mollier diagram of a two-stage cycle. In configuring the two-stage cycle, the case where the heat dissipation amount in the auxiliary radiator 2 is Qsub1 (FIG. 6A) and the case where Qsub2 is set (FIG. 6B) are compared (Qsub1 <Qsub2). As shown in FIG. 6, when the refrigeration capacity is constant, θh1 <θh2, so that heat is radiated with the heat radiation amount Qsub2 compared to the heat radiated with the heat radiation amount Qsub1 (enthalpy difference). ) Can be reduced (WH1> WH2). For this reason, if the suction temperature of the high-stage compressor 3 is low, the compressor power is reduced even with the same boost amount. Therefore, the input of the high stage compressor 3 can be reduced when the amount of heat radiation of the auxiliary radiator 2 is large.

  In the refrigeration apparatus of the present embodiment, constant control of the refrigeration capacity is performed, and COP = refrigeration capacity / (input of the high-stage compressor 3 + input of the low-stage compressor 1). If the input of the side compressor 3 can be reduced, the COP can be increased.

  By arranging the above contents, the COP can be maximized by the operation control in which the compression ratio of the high-stage compressor 3 and the compression ratio of the low-stage compressor 1 are substantially the same, and the auxiliary radiator 2 As the amount of heat released increases, the value of COP can be increased.

  Therefore, if the amount of heat released is just a saturated gas at the refrigerant outlet of the auxiliary radiator 2, the maximum COP can be obtained while avoiding liquid compression of the high stage compressor 3. The heat radiation amount of the auxiliary radiator 2 is ensured to such an extent that the refrigerant discharged from the low-stage compressor 1 is in a saturated gas state. Hereinafter, this heat dissipation amount is referred to as a required heat dissipation amount. In order to achieve this required heat dissipation amount, for example, the air volume of the radiator fan 8 is controlled or the structural design of the auxiliary radiator 2 itself is performed. Thus, by setting the heat radiation amount of the auxiliary radiator 2 to the required heat radiation amount, the maximum COP can be obtained while avoiding liquid compression of the high stage compressor 3.

  Here, if the compression ratio in the high stage side compressor 3 and the low stage side compressor 1 is controlled so that the low stage side condensation temperature is lower than the outside air temperature, cooling of the refrigerant in the auxiliary radiator 2 (heat radiation) ) Does not involve a phase change, it is possible to avoid the liquid compression of the high stage compressor 3 without fail. However, since the optimum intermediate pressure that makes the compression ratios of the high-stage compressor 3 and the low-stage compressor 1 substantially the same is not targeted, the maximum COP cannot be obtained.

  By the way, the required heat dissipation varies depending on the outside air temperature. Therefore, in order to obtain the maximum COP while avoiding liquid compression of the high-stage compressor 3 throughout the year, it is necessary to grasp the required heat dissipation amount under low outside air conditions and the required heat dissipation amount under high outside air conditions. It is necessary to keep. In the refrigeration apparatus of the present embodiment, there is a predetermined heat dissipation amount ratio according to the outside air condition between the required heat dissipation amount of the auxiliary radiator 2 and the heat dissipation amount of the high stage side radiator 4. Here, in this embodiment, since the auxiliary radiator 2 and the high-stage radiator 4 are configured by the integrated radiator 7, the predetermined heat dissipation ratio is based on the total heat dissipation of the integrated radiator 7. It is replaced with the ratio of the heat dissipation amount of the auxiliary radiator 2. Therefore, by setting the smaller heat dissipation rate ratio, which is the smaller one of the heat dissipation rate at low outside air conditions and the heat dissipation rate at high outside air conditions, liquid compression of the high stage compressor 3 is avoided throughout the year. However, a refrigeration apparatus capable of obtaining the maximum COP can be configured.

  As will be described later, the ratio of the heat dissipation amount of the auxiliary radiator 2 to the total heat dissipation amount in the integrated radiator 7 is smaller in the low outside air condition, and the monotonous change does not change with the change in the outside air temperature. It becomes a change. For this reason, if the auxiliary radiator 2 is configured with a heat dissipation rate in a low outside air condition, it is possible to secure a required heat dissipation amount that provides the maximum COP while avoiding liquid compression of the high stage compressor 3 throughout the year.

  In particular, in the refrigeration apparatus of the present embodiment, when the usage environment is assumed, if the heat release rate is set according to the lowest outdoor temperature condition throughout the year, liquid compression of the high stage compressor 3 can be avoided throughout the year. High reliability can be obtained.

  Hereinafter, prior to the description of the heat dissipation rate under the low outside air condition (7 ° C.) and the high outside air condition (35 ° C.) based on the JIS standard, the heat dissipation amount of the integrated radiator 7 as a whole will be described.

<Heat dissipation amount of integrated radiator 7>
FIG. 7 is a diagram for explaining the heat radiation amount of the integrated radiator 7 of the refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 7 shows a Mollier diagram of the refrigeration apparatus of the present embodiment. The heat radiation amount QALL of the integrated radiator 7 is an amount obtained by adding the heat radiation amount QCH of the high-stage side radiator 4 and the heat radiation amount Qsub of the auxiliary radiator 2 as in the following equation (1).

  QALL = Qsub + QCH (1)

<Rate of heat dissipation of auxiliary radiator 2 in integrated radiator 7>
When the heat radiation amount Qsub of the auxiliary radiator 2 is a required heat radiation amount, there is a relationship between the heat radiation amount Qsub and the heat radiation amount QALL of the entire integrated radiator 7 according to the outside air temperature and the physical properties of the CO ₂ refrigerant. . This relationship will be described below.

  FIG. 8 is a diagram for explaining a heat dissipation rate ratio of the auxiliary radiator in the integrated radiator of the refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 8 shows a Mollier diagram when the outside air temperature is 35 ° C. and the outside air temperature is 7 ° C.

For example, when the outside air temperature is 35 ° C., the ratio of the heat dissipation amount A1 of the high-stage radiator 4 and the heat dissipation amount B1 of the auxiliary radiator 2 in FIG. 8 is 67:33 based on the physical properties of the CO ₂ refrigerant. It has been decided. Further, when the outside air temperature is 7 ° C. (low ambient conditions), the heat radiation amount A2 of the high-stage radiator 4, the ratio of the heat radiation amount B2 of the auxiliary radiator 2 that is 83:17 of CO ₂ refrigerant Determined based on physical properties.

  As described above, the refrigeration apparatus according to the present embodiment is operated with the control that maximizes the COP, and is configured to obtain a high COP by securing the maximum heat radiation amount without being condensed by the auxiliary radiator 2. The ratio of the heat dissipation amount of the auxiliary radiator 2 to the total heat dissipation amount of the integrated radiator 7 is preferably 33% when the outside air temperature is 35 ° C. and 17% when the outside air temperature is 7 ° C. In view of the fact that this refrigeration system is used throughout the year, the total heat dissipation amount of the integrated radiator 7 is configured to radiate heat by the auxiliary radiator 2 at a ratio of 17% or less at a low outside air temperature of 7 ° C. Is desirable.

  Moreover, since the tendency of increase / decrease does not change with respect to the outside air temperature change, the ratio of the heat radiation amount of the auxiliary radiator 2 to the total heat radiation amount is monotonously increased or monotonously decreased with respect to the outside air temperature. Therefore, for example, if the auxiliary radiator 2 is configured with a heat dissipation rate at a minimum outside air temperature of 7 ° C., the required heat dissipation is obtained so that the maximum COP can be obtained while avoiding liquid compression of the high stage compressor 3 throughout the year. .

  Here, the outside temperature mentioned above is an example. It can set suitably according to the environment where a refrigerating device is arranged. For example, the temperature of the low outside air condition (predetermined low ambient temperature) is a temperature corresponding to the lower limit of the temperature assumed as the outside air temperature, and the temperature of the high outside air condition (predetermined high ambient temperature) is assumed as the outside air temperature. It is the temperature according to the upper limit of the temperature to be performed. The ratio of the heat dissipation amount of the auxiliary radiator 2 to the total heat dissipation amount of the integrated radiator 7 is the case where the auxiliary radiator 2 cools the refrigerant state to a substantially saturated gas state when the outside air temperature is a low outside air condition. What is necessary is just to comprise the auxiliary | assistant heat radiator 2 so that it may become lower than the thermal radiation amount ratio.

For example, the CO ₂ refrigerant used in the refrigeration apparatus of the present embodiment is a supercritical refrigerant. Therefore, the enthalpy difference of the high stage side radiator 4 is small, and since the specific heat ratio is large, the discharge temperature is high, and the enthalpy difference of the auxiliary radiator 2 is large. Therefore, the ratio of the heat dissipation amount of the auxiliary radiator 2 to the total heat dissipation amount of the integrated radiator 7 is large.

FIG. 9 is a diagram showing the heat release rate ratio of the auxiliary radiator 2 for each refrigerant. Next, a refrigerant that uses latent heat of condensation will be considered. In FIG. 9, the total heat dissipation of the integrated radiator 7 in the case of using a CO ₂ refrigerant and a typical refrigerant (propane, isobutane, ammonia, HFO1234yf, HFO1234ze, R134a, R410A, and R32) using latent heat of condensation. The ratio of the heat dissipation amount of the auxiliary radiator 2 with respect to is shown in a graph under a low outside air condition (7 ° C) and a high outside air condition (35 ° C).

When the condensation latent heat is used, in contrast to the CO ₂ refrigerant, the enthalpy difference of the high stage radiator 4 is large, and the enthalpy difference of the auxiliary radiator 2 is small. Therefore, the required heat dissipation amount ratio of the auxiliary radiator 2 with respect to the total heat dissipation amount of the integrated radiator 7 is smaller than the CO ₂ refrigerant. Among each refrigerant, the minimum heat release rate is 7.7% of isobutane, and the maximum heat release rate is 16.9% of R410A or R32. Therefore, in consideration of using a refrigerant that uses condensed latent heat other than CO ₂ refrigerant throughout the year, the auxiliary radiator 2 may be configured to radiate 8% or less of the total heat radiation amount of the integrated radiator 7. That would be desirable.

  In the refrigeration apparatus of the present embodiment, any configuration can be adopted as a specific configuration for achieving the above heat dissipation rate ratio. For example, when the auxiliary radiator 2 and the high-stage radiator 4 have a common radiator fan 8 as shown in FIG. 1, the heat transfer area of the auxiliary radiator 2 is set to the integrated radiator 7. 17% or less of the heat transfer area.

  Further, if the auxiliary radiator 2 and the high-stage radiator 4 use different radiator fans 8, the amount of heat radiation may be controlled by changing the rotational speed of each radiator fan 8. Good. In this case, each heat release is controlled by a control device (not shown) according to the outside air temperature so that the heat release rate is 17% when the outside air temperature is 7 ° C. and the heat release rate is 33% when the outside air temperature is 35 ° C. The fan 8 may be controlled.

  As described above, according to the present embodiment, the heat dissipation amount of the refrigerant of the auxiliary radiator 2 with respect to the total heat dissipation amount of the heat dissipation amount of the refrigerant of the high-stage side radiator 4 and the heat dissipation amount of the refrigerant of the auxiliary radiator 2. The ratio of the heat dissipation amount, which is the ratio of the heat dissipation amount, is set to be lower than the heat dissipation amount ratio when the heat dissipation amount of the auxiliary radiator 2 is set as the required heat dissipation amount under the low outside air condition. For this reason, the high stage side radiator 4 and the auxiliary radiator 2 are configured based on the amount of heat released at a low ambient temperature, so that the refrigerant in the auxiliary radiator 2 does not condense throughout the year, and the high stage compressor Since the liquid compression of 3 can be avoided, high reliability can be obtained. In addition, since starting and stopping of the compressor is suppressed and stable driving can be performed, an energy saving effect can be obtained. Here, in the present embodiment, the configuration of the high-stage side radiator 4 and the auxiliary radiator 2 is set based on the heat dissipation ratio (ratio). You may make it determine a structure based on relationship, such as ratio, about the thermal radiation amount of the refrigerant | coolant in the heat radiator 2. FIG.

In addition, regarding refrigeration systems that use CO ₂ refrigerant with low operating efficiency as a natural refrigerant that has little impact on global warming, year-round outdoor temperature changes, load fluctuations, refrigerant characteristics, high and low consumption Since the ratio of the amount of heat release was selected while taking into account the power ratio, the overall efficiency of the refrigeration system was improved while avoiding liquid compression of the high-stage compressor 3, resulting in energy saving effects throughout the year. Can be obtained. For example, since the heat radiation amount of the auxiliary radiator 2 is set to 17% or less with respect to the total heat radiation amount of the integrated radiator 7, even when CO ₂ refrigerant is used in the refrigeration apparatus, it is large throughout the year. Energy saving effect can be obtained.

  Furthermore, a compact refrigeration apparatus can be obtained by forming the auxiliary radiator 2 and the high-stage radiator 4 as an integrated radiator 7. Further, when the heat radiation amount of the auxiliary radiator 2 is set to 17% or less with respect to the total heat radiation amount of the integrated radiator 7, in the integrated radiator 7, the auxiliary radiator 2 and the high-stage side radiator 4 are transmitted. By configuring so as to divide the heat area, the integrated radiator 7 can be used without waste, and a compact refrigeration apparatus having high reliability and a large energy saving effect throughout the year can be obtained.

  In the refrigeration apparatus of the present embodiment, if the heat dissipation amount of the auxiliary radiator 2 is 17% or less with respect to the total heat dissipation amount of the integrated radiator 7, the auxiliary radiator 2 has high reliability and the highest energy saving effect. What is obtained is as described above. This is true when the integrated radiator 7 has a sufficient heat treatment capacity for the total heat radiation. On the other hand, for example, when the integrated radiator 7 does not have sufficient heat treatment capability, the high stage side high pressure becomes high, so the proportion of the auxiliary radiator 2 is reduced and assigned to the high stage radiator 4. The energy saving effect is greater. In addition, when the high stage side high pressure is excessively increased, the auxiliary radiator 2 must be assigned to the high stage side radiator 4 in order to ensure reliability. However, since the required heat dissipation amount cannot be obtained by the auxiliary radiator 2, the COP is greatly deteriorated as compared with the case where the required heat dissipation amount is obtained.

  Therefore, since the required heat radiation amount of the auxiliary radiator 2 can be obtained when the integrated radiator 7 has a sufficient heat treatment capability, the effect of the auxiliary radiator 2 in the two-stage cycle can be maximized. The integrated radiator 7 should have sufficient heat treatment capability.

  FIG. 10 is a diagram for explaining a sufficient heat treatment capability with respect to the heat radiation amount according to Embodiment 1 of the present invention. Based on FIG. 10, the sufficient heat treatment capability with respect to the heat radiation amount will be specifically described. The amount of heat released is the amount of heat exchange (refrigeration capacity) of the evaporator 6 (cooler) + the compressor input. For example, in the case of a COP = 2 single-stage cycle refrigeration system, since the refrigeration capacity is “2” with respect to the compressor input “1”, the heat release amount is “3”. Therefore, the heat treatment capacity of the radiator is generally designed to be about 1.5 times that of the cooler.

  Further, in the evaporator 6, in order to set the temperature difference between the refrigerant temperature (evaporation temperature) and the medium to be cooled (refrigerator air) to a desired temperature (for example, 10 ° C.), the refrigerant temperature (condensation temperature) of the radiator and the outside air If the temperature difference from the temperature is the desired temperature (for example, 10 ° C.), sufficient heat treatment capability is obtained. For example, in the integrated radiator 7 of the two-stage cycle refrigeration system as in the present embodiment, the temperature difference between the refrigerant temperature (condensation temperature) and the outside air temperature is expressed as the refrigerant temperature (condensation temperature) and the outside air temperature of the radiator. If the temperature difference is equal to or less than 10 ° C. (for example, 10 ° C. or less), it is possible to reliably obtain a COP higher than that of the single stage cycle including the effect of the auxiliary radiator 2.

  Here, the heat treatment capacity is represented by the product of the heat transfer area and the heat transfer rate of the heat exchanger. The heat transfer rate is mainly determined by the heat transfer rate on the refrigerant side and the heat transfer rate on the air side. The cooler for low-temperature equipment has a large heat transfer area because the pitch of the heat transfer tubes and fins is large and the heat passage rate is smaller than that of the radiator from the viewpoint of improving the frost resistance, but the heat treatment capacity is smaller than that of the radiator.

Embodiment 2. FIG.
FIG. 11 is a diagram showing a configuration of a refrigeration apparatus according to Embodiment 2 of the present invention. In FIG. 11, the same reference numerals as those in FIG. 1 and the like perform the same operations and the like as described in the first embodiment. As shown in FIGS. 11A and 11B, the refrigeration apparatus of the present embodiment includes an accumulator 9 in a path between the auxiliary radiator 2 and the high stage compressor 3 in the refrigerant circuit. Even if the liquid refrigerant condensed in the auxiliary radiator 2 is generated, the accumulator 9 can store the liquid, and gas-liquid separation can be performed. For this reason, since only the gas refrigerant can flow out to the high stage side compressor 3, liquid compression of the high stage side compressor 3 can be avoided.

  In particular, in FIG. 11B, the accumulator 9 includes an outlet for the liquid refrigerant stored by gas-liquid separation, and performs flow rate adjustment, pressure reduction, etc. via the flow rate control valve 10 to the upstream side of the evaporator 6. It is set as the structure which flows a liquid refrigerant and merges with the refrigerant | coolant which passed the high stage | side heat radiator 4 and the expansion valve 5. FIG. In the refrigeration apparatus of FIG. 11 (b), the intermediate pressure refrigerant in the accumulator 9 can be directly guided to the evaporator 6 without undergoing processes such as compression and condensation. The energy saving effect can also be obtained.

  The refrigeration apparatus of this embodiment is also widely applied to refrigeration or refrigeration equipment such as showcases, commercial refrigeration refrigerators, vending machines, etc. that require non-fluorocarbons, reduction of chlorofluorocarbon refrigerants, and energy saving of equipment. be able to.

  1 Low stage compressor, 2 auxiliary radiator, 3 high stage compressor, 4 high stage radiator, 5 expansion valve, 6 evaporator, 7 integrated radiator, 8 radiator fan, 9 accumulator, 10 flow rate Control valve, 11 refrigerator, 12 indoor unit, 13 liquid refrigerant piping, 71 heat transfer fin, 72 heat transfer tube.

Claims (11)

A low-stage compressor that compresses and discharges the refrigerant;
Heat exchange between the refrigerant discharged from the low-stage compressor and ambient air, and an auxiliary radiator that radiates heat from the refrigerant;
A high-stage compressor that compresses and discharges the refrigerant radiated by the auxiliary radiator; and
Heat exchange between the refrigerant discharged from the high-stage compressor and the ambient air, and at least a high-stage radiator that radiates heat from the refrigerant;
The sum of the amount of heat released from the refrigerant to the saturated gas state in the auxiliary radiator and the amount of heat released from the refrigerant in the high-stage radiator when the temperature of the ambient air is a predetermined low ambient temperature. The refrigerator comprising the high-stage side radiator and the auxiliary radiator based on a predetermined heat dissipation amount ratio that is a ratio of a heat dissipation amount of the refrigerant in the auxiliary radiator to a heat dissipation amount.   The heat dissipation ratio, which is the ratio of the heat dissipation amount of the refrigerant in the auxiliary radiator to the total heat dissipation amount of the refrigerant in the high-stage radiator and the heat dissipation amount of the refrigerant in the auxiliary radiator, The refrigerator according to claim 1, wherein the high stage side radiator and the auxiliary radiator are configured so as to be equal to or less than a predetermined heat dissipation ratio.   The refrigerator according to claim 1 or 2, wherein the predetermined low ambient temperature is a temperature corresponding to an assumed lower limit value of air that is not to be cooled.   The capacity ratio between the capacity of the low-stage compressor and the capacity of the high-stage compressor is adjusted so that the compression ratio of the low-stage compressor is equal to the compression ratio of the high-stage compressor. The refrigerator as described in any one of Claims 1-3 characterized by the above-mentioned. The high stage side radiator is
The temperature difference between the refrigerant flowing through the high-stage radiator and the ambient air is equal to or less than the temperature difference between the refrigerant flowing through the cooler that evaporates the refrigerant and the heat exchange target of the refrigerant in the cooler. It has heat processing capability, The refrigerator as described in any one of Claims 1-4 characterized by the above-mentioned. The high-stage side radiator and the auxiliary radiator are constituted by an integrated radiator that integrates heat transfer fins,
The refrigerator according to any one of claims 1 to 5, further comprising a blower that allows the ambient air to pass through the integrated radiator.   The gas-liquid separator which makes the said high stage side compressor suck | inhale a gaseous refrigerant | coolant is further provided between the said auxiliary | assistant heat radiator and the said high stage side compressor, The any one of Claims 1-6 characterized by the above-mentioned. The refrigerator according to one item. A liquid refrigerant pipe connected to the liquid refrigerant outlet of the gas-liquid separator and joined with the refrigerant flowing out of the high-stage radiator;
The refrigerator according to claim 7, further comprising a flow rate adjusting device that adjusts an amount of refrigerant passing through the connection pipe.   The refrigerator according to any one of claims 1 to 8, wherein carbon dioxide is used as the refrigerant, and the heat release rate ratio is set to 17% or less.   9. The refrigerant according to claim 1, wherein at least one of propane, isobutane, ammonia, HFO1234yf, HFO1234ze, R134a, R410A, and R32 is used as the refrigerant, and the heat dissipation rate ratio is 8% or less. The refrigerator according to one item. A low-stage compressor, an auxiliary radiator, a high-stage compressor, and a high-stage radiator in the refrigerator according to any one of claims 1 to 10,
A decompression device that decompresses the refrigerant radiated by the high-stage radiator;
A refrigeration apparatus comprising a refrigerant circuit connected by piping to a cooler that evaporates the refrigerant decompressed by the decompression device.

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