JP5367100B2 - Dual refrigeration equipment - Google Patents

Description

  The present invention relates to a binary refrigeration apparatus, and more particularly to a binary refrigeration apparatus provided with a heat storage tank for storing cold energy.

  Conventionally, as a device for cooling at a low temperature of minus several tens of degrees, a high-source refrigeration cycle that is a refrigeration cycle device for circulating a high-temperature side refrigerant, and a refrigeration cycle device for circulating a low-temperature side refrigerant A binary refrigeration device having a certain low-source refrigeration cycle is used. For example, in a binary refrigeration system, a low-source refrigeration cycle and a high-source refrigeration cycle are configured by a cascade condenser configured to exchange heat between a low-source side condenser in a low-source refrigeration cycle and a high-source side evaporator in a high-source refrigeration cycle. Are linked.

  In addition, the heat storage medium can store heat so that the surplus capacity on the heat source side can be used effectively at night when the cooling load is low and only low refrigeration capacity is required. There has been proposed one that achieves an effect such as promotion and reduction of the power consumption rate (for example, see Patent Document 1).

JP 2010-271000 A (paragraph [0014])

  In the conventional binary refrigeration apparatus, a low-source refrigeration cycle and a high-source refrigeration cycle are integrally assembled via a cascade condenser, and when the low-source refrigeration cycle is operated, the high-source refrigeration cycle is also operated simultaneously. In such a binary refrigeration apparatus, when the high refrigeration cycle stops due to a failure or a power failure, the heat exchange of the refrigerant in the cascade condenser (condenser) becomes insufficient in the low refrigeration cycle. As a result, the refrigerant pressure in the low-source refrigeration cycle rises to a saturation pressure corresponding to the ambient temperature on the condenser side with a large amount of refrigerant, and the refrigerant may be released to the atmosphere from a safety valve or the like provided in the refrigerant circuit. . For this reason, there existed a problem that a low original refrigeration cycle and a high original refrigeration cycle cannot be operated separately.

In addition, when a liquid receiver is provided in the low-source refrigeration cycle, when the high-source refrigeration cycle stops due to a failure or the like, a high-temperature and high-pressure refrigerant flows into the liquid receiver. For this reason, there has been a problem that the temperature of the liquid receiver rises and the refrigerant pressure rises accordingly. In particular, when CO ₂ refrigerant is used in the low-source refrigeration cycle, a supercritical state may occur due to an increase in ambient temperature, and the density of the refrigerant flowing into the liquid receiver decreases. For this reason, the volume of the liquid receiver required for maintaining the refrigerant pressure flowing into the liquid receiver below the design pressure becomes excessive, or the design pressure of the refrigerant circuit needs to be increased. Thereby, there existed a problem that an increase in weight, lack of compactness, and a manufacturing cost increased.

  The present invention has been made to solve the above-described problems. In a binary refrigeration apparatus in which two refrigerant circuits are combined, the pressure rises even if the ambient temperature rises when the binary refrigeration apparatus is stopped. It is possible to obtain a binary refrigeration apparatus that can be suppressed and can improve reliability.

  A binary refrigeration apparatus according to the present invention includes a first refrigerant circuit that connects a first compressor, a first condenser, a first expansion device, a first evaporator, and a first heat storage evaporator to circulate refrigerant. A second compressor, a second condenser, a liquid receiver, a second throttling device, and a second evaporator, and a second refrigerant circuit that circulates the refrigerant, the first evaporator, and the second condenser A cascade condenser that exchanges heat between the refrigerant flowing through the first evaporator and the refrigerant flowing through the second condenser, the first heat storage evaporator, and the liquid receiver, The first heat storage evaporator cools the heat storage medium to store the cold heat, and includes a heat storage tank that cools the liquid receiver by the cold heat stored in the heat storage medium.

  The present invention accommodates a first heat storage evaporator and a liquid receiver, cools the heat storage medium by the first heat storage evaporator to store cold energy, and cools the liquid receiver by the cold heat stored in the heat storage medium. Since the heat storage tank is provided, it is possible to suppress an increase in pressure accompanying a temperature increase of the liquid receiver, and to improve reliability.

FIG. 3 is a refrigerant circuit diagram of the binary refrigeration apparatus according to Embodiment 1 of the present invention. It is a refrigerant circuit figure of the binary refrigeration apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure of the binary refrigeration apparatus which concerns on Embodiment 3 of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a binary refrigeration apparatus according to the invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram of a binary refrigeration apparatus according to Embodiment 1 of the present invention. In FIG. 1, the binary refrigeration apparatus includes a low-source refrigeration cycle 10 and a high-source refrigeration cycle 20, and configures a refrigerant circuit that circulates refrigerant independently of each other. Further, the binary refrigeration apparatus includes a control device 33 that performs operation control of the entire binary refrigeration apparatus.

  The low-source refrigeration cycle 10 includes a low-side compressor 11, a low-side condenser 12, a low-side liquid receiver 13, a low-side expansion valve 15, and a low-side evaporator 16 in order. A refrigerant circuit (hereinafter referred to as a low-source-side refrigerant circuit) is configured by connecting with pipes.

  The low-source refrigeration cycle 10 corresponds to the “second refrigerant circuit” in the present invention. The low-side compressor 11 corresponds to a “second compressor”, the low-side condenser 12 corresponds to a “second condenser”, and the low-side receiver 13 serves as a “receiver”. The low-side expansion valve 15 corresponds to a “second throttle device”, and the low-side evaporator 16 corresponds to a “second evaporator”.

  The high-source refrigeration cycle 20 includes a high-side compressor 21, a high-side condenser 22, a high-side expansion valve 23, a high-side evaporator 24, and a high-side heat storage evaporator 25 in order. A refrigerant circuit (hereinafter referred to as a high-side refrigerant circuit) is configured by connecting with pipes.

  The high refrigeration cycle 20 corresponds to the “first refrigerant circuit” in the present invention. The high-end compressor 21 corresponds to a “first compressor”, the high-end condenser 22 corresponds to a “first condenser”, and the high-end expansion valve 23 corresponds to a “first throttle device”. The high-end side evaporator 24 corresponds to a “first evaporator”, and the high-end side heat storage evaporator 25 corresponds to a “first heat storage evaporator”.

  In addition, since the low-side refrigerant circuit and the high-side refrigerant circuit have a multi-stage configuration, heat exchange between the high-side evaporator 24 and the low-side condenser 12 can be performed between the refrigerants passing through the high-side evaporator 24 and the low-side condenser 12. A cascade capacitor 30 configured to be coupled to is provided. Here, in the configuration referred to as the low element side and the high element side, the level of temperature, pressure, etc. is not particularly determined in relation to absolute values, but the state in the system, device, etc. It shall be relatively determined in operation and the like.

  The low-side compressor 11 sucks the refrigerant flowing through the low-side refrigerant circuit, compresses the refrigerant, and discharges it in a high temperature / high pressure state. The low-side compressor 11 is formed of a compressor of a type that can control the number of revolutions by, for example, an inverter circuit and adjust the refrigerant discharge amount.

The low-source side condenser 12 condenses the refrigerant into a liquid refrigerant (condenses and liquefies). In the present embodiment, for example, the low-condenser 12 is configured by a heat transfer tube or the like through which the refrigerant flowing in the low-side refrigerant circuit passes in the cascade capacitor 30, and heat exchange with the refrigerant flowing in the high-side refrigerant circuit is performed. Shall be.
The low source side liquid receiver 13 is provided on the downstream side of the low source side condenser 12 and stores the refrigerant.

  The low-side expansion valve 15 decompresses and expands the refrigerant flowing through the low-side refrigerant circuit. For example, it is configured by an arbitrary pressure reducing device such as a flow rate control means such as an electronic expansion valve, a capillary (capillary), a refrigerant flow rate adjusting means such as a temperature-sensitive expansion valve, or a throttling device.

  The low element side evaporator 16 evaporates the refrigerant flowing through the low element refrigerant circuit by heat exchange with the object to be cooled, for example, and converts it into a gas (gas) refrigerant (evaporated gas). The object to be cooled is cooled directly or indirectly by heat exchange with the refrigerant.

  The high-end compressor 21 sucks the refrigerant flowing through the high-end refrigerant circuit, compresses the refrigerant, and discharges it in a high temperature / high pressure state. The high-end compressor 21 includes, for example, an inverter circuit and is configured with a compressor of a type that can adjust the refrigerant discharge amount.

  The high-side condenser 22 performs heat exchange between, for example, air, brine, and the refrigerant flowing through the high-side refrigerant circuit to condense and liquefy the refrigerant. In the present embodiment, heat exchange between the outside air and the refrigerant is performed, and a high-side condenser fan is provided to promote heat exchange. The high-end condenser fan is also configured with a fan that can adjust the air volume.

  The high-side expansion valve 23 decompresses and expands the refrigerant flowing through the high-side refrigerant circuit. For example, it is configured by an arbitrary pressure reducing device, a throttle device, or the like that can control the throttle amount, such as a flow rate control means such as an electronic expansion valve, a refrigerant flow rate control means, or the like.

  The high element side evaporator 24 evaporates the refrigerant flowing through the high element side refrigerant circuit by heat exchange. In the present embodiment, for example, in the cascade condenser 30, the high-side evaporator 24 is configured by a heat transfer tube through which the refrigerant flowing through the high-side refrigerant circuit passes, and heat exchange with the refrigerant flowing through the low-side refrigerant circuit is performed. Shall be.

  The cascade condenser 30 includes a high-side evaporator 24 and a low-side condenser 12, and makes it possible to exchange heat between the refrigerant flowing through the high-side evaporator 24 and the refrigerant flowing through the low-side condenser 12. It is an intermediate heat exchanger. By configuring the high-side refrigerant circuit and the low-side refrigerant circuit in multiple stages via the cascade capacitor 30 and performing heat exchange between the refrigerants, independent refrigerant circuits can be linked.

  In addition, the binary refrigeration apparatus of the present embodiment includes a heat storage tank 31 that houses the low-source side liquid receiver 13 and the high-source side heat storage evaporator 25. A heat storage medium 32 such as brine or water is stored in the heat storage tank 31. The heat storage tank 31 has a function of storing the cold energy given from the high-side heat storage evaporator 25 in the heat storage medium 32 in the heat storage tank 31. In addition, the heat storage tank 31 has a function of cooling the low-source side liquid receiver 13 by the cold energy stored in the heat storage medium 32.

  The control device 33 includes a high pressure sensor (not shown) that measures the refrigerant pressure on the discharge side of the high-end compressor 21, a low-pressure sensor (not shown) that measures the refrigerant pressure on the suction side, A temperature sensor (not shown) for measuring the evaporation temperature of the side evaporator 24, and a temperature sensor (not shown) for measuring the outlet side temperature of the high side evaporator 24 in order to detect the degree of supercooling at the outlet of the high side evaporator 24 The high-source refrigeration cycle 20 such as a temperature sensor (not shown) that measures the outlet-side temperature of the high-side heat storage evaporator 25 to detect the degree of supercooling at the outlet of the high-side heat storage evaporator 25. Various measurement information necessary for the operation control is input. Measurement information from a temperature sensor (not shown) that measures the temperature of the heat storage medium 32 stored in the heat storage tank 31 is input to the control device 33. Note that the evaporation temperature of the high-end evaporator 24 may be measured by a temperature sensor provided in the high-end evaporator 24, or may be calculated from the low pressure of the high-end refrigerant circuit.

  Based on the measurement information input from each sensor, the operation content (set temperature, etc.) instructed by the user from an operation device (not shown), the control device 33 is connected to the low-side compressor 11 and the high-side compressor. The operation frequency (capacity) 21, the throttle amount of the high-side expansion valve 23, the rotational speed of the high-side condenser fan, and the like are controlled.

In the binary refrigeration apparatus, some devices (for example, the low element side evaporator 16) of the low element refrigeration cycle 10 may be arranged in an indoor load device such as a showcase installed in a supermarket or the like. For example, if the refrigerant circuit is opened by changing the connection of pipes by rearranging the showcase or the like, the possibility of refrigerant leakage increases. Therefore, here, CO ₂ (carbon dioxide) having a small influence on global warming is used as the refrigerant circulating in the low-side refrigerant circuit of the low-source refrigeration cycle 10 in consideration of refrigerant leakage. On the other hand, since the refrigerant circuit used in the high refrigeration cycle 20 does not open the refrigerant circuit in the high refrigeration cycle 20, for example, an HFC refrigerant having a high global warming potential can be used. Nevertheless, it is desirable to use a refrigerant having a small influence on global warming, such as HFO refrigerant (HFO1234yf, HFO1234ze, etc.), HC refrigerant, CO ₂ , ammonia, water, and the like. Therefore, in the present embodiment, an HFO refrigerant is used as a refrigerant that circulates in the high-side refrigerant circuit of the high-source refrigeration cycle 20.

(Overview of operation)
Next, the outline | summary of operation | movement of the binary refrigeration apparatus which consists of the above structures is demonstrated. First, the operation of the high-source refrigeration cycle 20 is performed prior to the operation of cooling the refrigeration load (or may be performed simultaneously), and the cold energy is stored in the heat storage medium 32 (brine, water, etc.) of the heat storage tank 31. The low-source side liquid receiver 13 itself and the internal refrigerant are cooled by the cold energy stored in the heat storage medium 32.

  The operation | movement of each component apparatus in the cooling operation of the above binary refrigeration apparatuses is demonstrated based on the flow of the refrigerant | coolant which circulates through each refrigerant circuit.

(Operation of high-source refrigeration cycle 20)
First, the operation of the high-source refrigeration cycle 20 will be described. The high-end compressor 21 sucks in the HFO refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the high-side condenser 22. The high-side condenser 22 exchanges heat between the outside air supplied from the high-side condenser fan and the HFO refrigerant, and condenses and liquefies the HFO refrigerant. The condensed and liquefied refrigerant passes through the high-side expansion valve 23. The high-side expansion valve 23 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the high-side evaporator 24 (cascade capacitor 30). The high-side evaporator 24 evaporates the refrigerant by heat exchange with the refrigerant passing through the low-side condenser 12. Furthermore, the evaporated refrigerant flows into the high-side heat storage evaporator 25 (heat storage tank 31). The high-source side heat storage evaporator 25 evaporates and gasifies the refrigerant by heat exchange with the heat storage medium 32 accommodated in the heat storage tank 31. The high-end compressor 21 sucks the HFO refrigerant completely evaporated and gasified.

(Operation of low-source refrigeration cycle 10)
Next, the operation of the low-source refrigeration cycle 10 will be described. The low-source compressor 11 sucks CO ₂ refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the low-side condenser 12 (cascade capacitor 30). The low-side condenser 12 condenses the refrigerant by heat exchange with the refrigerant passing through the high-side evaporator 24. Furthermore, the condensed refrigerant flows into the low-source side receiver 13 (heat storage tank 31). The low-source side liquid receiver 13 is cooled by the heat storage medium 32 accommodated in the heat storage tank 31, and the internal refrigerant condenses. The completely condensed and liquefied refrigerant passes through the low-side expansion valve 15. The low-side expansion valve 15 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the low-side evaporator 16. The low-source evaporator 16 evaporates the refrigerant by exchanging heat with the object to be cooled. The high-end compressor 21 sucks the CO ₂ refrigerant that has been vaporized.

(Operation of the low refrigeration cycle 10 when the high refrigeration cycle 20 is stopped)
The binary refrigeration apparatus in the present embodiment can avoid an increase in pressure due to a temperature increase in the low-source side receiver 13 even when the operation is stopped due to a failure of the high-source refrigeration cycle 20 or the like. The operation of the low-source refrigeration cycle 10 when the high-source refrigeration cycle 20 is stopped will be described.
The low-source compressor 11 sucks CO ₂ refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the low-side condenser 12 (cascade capacitor 30). Since the high-source refrigeration cycle 20 is stopped, the low-source side condenser 12 does not sufficiently exchange heat with the refrigerant passing through the high-source refrigeration cycle 20, and the low-source side receiver in a high temperature / high pressure state. 13 (heat storage tank 31). When a CO ₂ refrigerant is used, it may flow into the low-source side receiver 13 in a supercritical state due to an increase in ambient temperature. The low source side liquid receiver 13 is cooled by the heat storage medium 32 accommodated in the heat storage tank 31, and the refrigerant flowing into the low source side liquid receiver 13 is cooled. Thereby, the pressure rise accompanying the temperature rise of a refrigerant | coolant is suppressed. The refrigerant that has flowed out of the low source side liquid receiver 13 passes through the low source side expansion valve 15 and the low source side evaporator 16 and is again sucked into the high source side compressor 21.

  As described above, in the present embodiment, the high-side heat storage evaporator 25 and the low-side heat receiver 13 are accommodated, and the high-side heat storage evaporator 25 cools the heat storage medium 32 to store cold energy. At the same time, a heat storage tank 31 for cooling the low-source side liquid receiver 13 by the cold energy stored in the heat storage medium 32 is provided. For this reason, a heat storage operation is performed in the high-source refrigeration cycle 20, and the low-source side liquid receiver 13 can be cooled by the cold storage heat. Thereby, even if the high-source refrigeration cycle 20 is stopped due to a failure or the like, it is possible to suppress an increase in pressure due to the temperature increase of the low-source side liquid receiver 13 by the cold energy stored in the heat storage tank 31. Therefore, the reliability of the binary refrigeration apparatus can be improved. Further, it is not necessary to set an excessively large liquid receiver or a high design pressure, and an effect of cost reduction can be expected.

  In addition, when the operation of the high-source refrigeration cycle 20 is stopped, it is desirable that the operation of the low-source refrigeration cycle 10 is also stopped. Even if the ambient temperature rises when the operation of the high-source refrigeration cycle 20 and the low-source refrigeration cycle 10 is stopped, the pressure rise accompanying the temperature rise of the low-source side receiver 13 due to the cold stored in the heat storage tank 31. Can be suppressed. Therefore, the reliability of the binary refrigeration apparatus can be improved. Further, it is not necessary to set an excessively large liquid receiver or a high design pressure, and an effect of cost reduction can be expected.

Embodiment 2. FIG.
FIG. 2 is a refrigerant circuit diagram of the binary refrigeration apparatus according to Embodiment 2 of the present invention. In FIG. 2, in addition to the configuration of the first embodiment, the low-source refrigeration cycle 10 includes a low-source side heat storage condenser 14 between the low-source side receiver 13 and the low-source side expansion valve 15. Yes.
In the heat storage tank 31 of the present embodiment, a low-source side receiver 13, a low-source-side heat storage condenser 14, and a high-source-side heat storage evaporator 25 are accommodated and given from the high-source-side heat storage evaporator 25. The stored cold heat is stored in the heat storage medium 32 in the heat storage tank 31, and the low-source side liquid receiver 13 and the low-source side heat storage condenser 14 are cooled by the cold heat stored in the heat storage medium 32. The low-source-side heat storage condenser 14 corresponds to a “second heat storage evaporator”.

  The binary refrigeration apparatus in the present embodiment moves the cold on the low temperature side to the high temperature side via the heat storage medium 32 in the heat storage tank 31 by the refrigerant used in the high refrigeration cycle 20 and the low refrigeration cycle 10. is there. Since the operation efficiency during this time is via the heat storage medium 32 (brine, water, etc.), the temperature difference between the refrigerants is larger than that in the direct heat exchange of the cascade condenser 30 and the operation efficiency is lowered. However, it is possible to level the cooling load by heat storage operation such as at night, and the operation efficiency of the refrigeration cycle by stable operation is improved, which more than compensates for the decrease in operation efficiency due to heat exchange in the heat storage tank 31.

  It supplements about the effect of stable operation by cooling load leveling. The refrigerator is designed to have a maximum operating efficiency when used at a rated environmental condition of 32 ° C. outside air. Use in environments outside the rated conditions can lead to significant performance degradation. Specifically, the compressor operation at a high outside air temperature has a high compression ratio and high rotation, and at a low outside air temperature, the compressor has a low compression ratio and low rotation. In particular, in the two-stage refrigeration apparatus, since two compressors are used, the compression process is divided, and there is a concern that the performance may be deteriorated due to a lower compression ratio than a normal refrigerator. For this reason, the compression ratio and the rotational speed are stabilized by the heat load leveling operation by the heat storage operation at the time of low outside air such as nighttime or the heat storage use operation at the time of the high outside air such as daytime, and the reduction of the operation efficiency can be avoided.

  The binary refrigeration apparatus of the present embodiment enables independence between the high unit side and the low unit side, and the independence of the refrigerator design, installation capacity, and service is promoted.

  If the high-source refrigeration cycle 20 is used as a heat pump and switched so that the refrigerant heat of the low-side condenser 12 can be used, a heat recovery operation of refrigeration and refrigeration heat can be performed as a heat source for heating or hot water supply.

For example, when the refrigerant is ammonia, the refrigerant piping connection to the manned space at the site is not preferable because of toxicity. Since hydrocarbon (HC) is also a flammable gas, there are restrictions on the amount of charge used. Fluorocarbon (HFC) is a warming gas and these refrigerants should avoid local piping as much as possible to prevent gas leakage. In the present embodiment, the high-source refrigerant circuit (ammonia, HC, HFC, etc.) is separated from the cascade condenser 30. In manned space, carbon dioxide (CO _2, etc.) is used for the low-source refrigerant circuit. It is safe.

In the binary refrigeration apparatus having such a configuration, a part of the low refrigeration cycle 10 (for example, the low original evaporator 16) is disposed in an indoor load device such as a showcase installed in a supermarket or the like. There are things to do. For example, if the refrigerant circuit is opened by changing the connection of pipes by rearranging the showcase or the like, the possibility of refrigerant leakage increases. Therefore, here, CO ₂ (carbon dioxide) having a small influence on global warming is used as the refrigerant circulating in the low-side refrigerant circuit of the low-source refrigeration cycle 10 in consideration of refrigerant leakage. On the other hand, since the refrigerant circuit used in the high refrigeration cycle 20 does not open the refrigerant circuit in the high refrigeration cycle 20, for example, an HFC refrigerant having a high global warming potential can be used. Nevertheless, it is desirable to use a refrigerant having a small influence on global warming, such as HFO refrigerant (HFO1234yf, HFO1234ze, etc.), HC refrigerant, CO ₂ , ammonia, water, and the like. Therefore, in the present embodiment, an HFO refrigerant is used as a refrigerant that circulates in the high-side refrigerant circuit of the high-source refrigeration cycle 20.

  The operation | movement of each component apparatus in the cooling operation of the above binary refrigeration apparatuses is demonstrated based on the flow of the refrigerant | coolant which circulates through each refrigerant circuit.

(Operation of high-source refrigeration cycle 20)
First, the operation of the high-source refrigeration cycle 20 will be described. The high-end compressor 21 sucks in the HFO refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the high-side condenser 22. The high-side condenser 22 exchanges heat between the outside air supplied from the high-side condenser fan and the HFO refrigerant, and condenses and liquefies the HFO refrigerant. The condensed and liquefied refrigerant passes through the high-side expansion valve 23. The high-side expansion valve 23 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the high-side evaporator 24 (cascade capacitor 30). The high-side evaporator 24 evaporates the refrigerant by heat exchange with the refrigerant passing through the low-side condenser 12. Furthermore, the evaporated refrigerant flows into the high-side heat storage evaporator 25 (heat storage tank 31). The high-source side heat storage evaporator 25 evaporates and gasifies the refrigerant by heat exchange with the heat storage medium 32 accommodated in the heat storage tank 31. The high-end compressor 21 sucks the HFO refrigerant completely evaporated and gasified.

(Operation of low-source refrigeration cycle 10)
Next, the operation of the low-source refrigeration cycle 10 will be described. The low-source compressor 11 sucks CO ₂ refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the low-side condenser 12 (cascade capacitor 30). The low-side condenser 12 condenses the refrigerant by heat exchange with the refrigerant passing through the high-side evaporator 24. The condensed refrigerant is stored in the low-source side receiver 13 and flows into the low-source side heat storage condenser 14 (heat storage tank 31). The low-source-side heat storage condenser 14 condenses the refrigerant by heat exchange with the heat storage medium 32 accommodated in the heat storage tank 31. The completely condensed and liquefied refrigerant passes through the low-side expansion valve 15. The low-side expansion valve 15 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the low-side evaporator 16. The low-source evaporator 16 evaporates the refrigerant by exchanging heat with the object to be cooled. The high-end compressor 21 sucks the CO ₂ refrigerant that has been vaporized.

(Operation according to the cooling load)
In the binary refrigeration apparatus of the present embodiment, for example, in the high-side compressor 21, the frequency of the motor to be driven is controlled, and the cooling capacity in the high-side refrigeration cycle 20 is controlled, thereby discharging in the low-side refrigerant circuit. Adjust the side pressure (low source side high pressure). In the cascade capacitor 30, a temperature difference ΔT between the condensation temperature of the low-source side condenser 12 (low-source-side condensation temperature) and the evaporation temperature of the high-side evaporator 24 (high-source-side evaporation temperature) occurs. Although the temperature difference ΔT varies depending on the heat exchange amount of the cascade capacitor 30, it is set to about 5 ° C. here, for example. If the operating frequency of the high-side compressor 21 is increased from a certain operating state to increase the high-side cooling capacity, the high-side evaporation temperature decreases. Along with the reduced high element side evaporation temperature, the low element side condensation temperature (low element side high pressure) also decreases. Conversely, if the cooling capacity on the high element side is reduced, the low element side high pressure is also increased.

  In the dual refrigeration apparatus of the present embodiment, the cooling load changes according to the outside air temperature, and the refrigeration capacity (corresponding to the evaporation capacity on the low-source refrigeration cycle 10 side) is determined with respect to the cooling load. And the refrigerant | coolant flow volume is controlled by the low-source side compressor 11 so that the required refrigerating capacity can be obtained.

  Hereinafter, each operation operation of the normal operation mode, the heat storage operation mode, and the heat storage use operation mode will be described according to the size of the cooling load.

<Cooling load: Normal>
When the cooling load is normal (such as an intermediate period), the normal operation mode in which the heat storage tank 31 is not stored or used is performed. In this normal operation mode, high-efficiency operation is performed using a cascade capacitor 30 that directly exchanges heat between refrigerants. In the present embodiment, the high-source side refrigerant circuit is connected so that the refrigerant flows in the order from the cascade capacitor 30 to the heat storage tank 31, and the low-source side refrigerant circuit is set so that the refrigerant flows in the order from the cascade capacitor 30 to the heat storage tank 31. Since they are connected, most of the heat exchange is performed by the cascade capacitor 30.

  The control device 33 controls the throttle amount of the high-side expansion valve 23 so that the refrigerant superheat degree at the outlet of the cascade condenser 30 (high-side evaporator 24) becomes a predetermined value (for example, about 2 ° C.). As a result, the refrigerant in the high-end refrigerant circuit at the outlet of the cascade capacitor 30 is completely evaporated. Accordingly, the refrigerant in the low-side refrigerant circuit is also completely condensed by the cascade condenser 30 (low-side condenser 12). For this reason, the heat exchange required by the cascade condenser 30 can be implemented more reliably.

  Further, the control device 33 controls the capacity of the high-side compressor 21 so that the evaporation temperature of the high-side evaporator 24 is substantially equal to the temperature of the heat storage medium 32. As a result, the refrigerant temperature of the high-side refrigerant circuit passing through the high-side heat storage evaporator 25 substantially matches the temperature of the heat storage medium 32, and heat exchange is performed between the refrigerant of the high-side refrigerant circuit and the heat storage medium 32. Not done. On the other hand, as described above, in the present embodiment, there is a temperature difference ΔT (for example, about 5 ° C.) between the low-side condensation temperature and the high-side evaporation temperature. For this reason, the amount of refrigerant filled is set so that the low-side condensation temperature is higher than the high-side evaporation temperature, but the liquid supercooling degree at the outlet of the low-side heat storage condenser 14 is about 0 ° C. (saturated liquid) to about 2 ° C. By adjusting, the refrigerant temperature of the low-side refrigerant circuit passing through the low-side heat storage condenser 14 and the temperature of the heat storage medium 32 substantially match, and heat is exchanged between the low-side refrigerant circuit and the heat storage medium 32. Is not done. Therefore, in the normal operation mode, heat exchange through the heat storage medium 32 is not performed in the heat storage tank 31, and heat exchange by the cascade capacitor 30 can be performed, so that highly efficient operation is possible.

  In addition, the liquid subcooling degree of the refrigerant | coolant stored by the low source side liquid receiver 13 can be expanded by cooling the low source side liquid receiver 13 accommodated in the heat storage tank 31 with the cold of the heat storage medium 32. Further, it is possible to obtain a further refrigeration effect and to improve the operation efficiency.

<Cooling load: small>
When the cooling load is small (in winter, at night, etc.), a heat storage operation mode is performed in which the heat storage medium 32 is cooled by the high-source side refrigerant circuit (high-source side heat storage evaporator 25) to store cold energy. In this heat storage operation mode, while performing high efficiency operation using the cascade condenser 30 that directly exchanges heat between the refrigerants, the heat storage operation is performed in which the heat storage medium 32 is cooled by the high-source side heat storage evaporator 25 to store the cold energy. When the cooling load is small, the heat exchange amount of the cascade condenser 30 is reduced, so that the cooling capacity of the high-source side refrigerant circuit becomes excessive as compared with the cooling load. For this reason, the refrigerant in the high-end side refrigerant circuit does not completely evaporate in the cascade capacitor 30 (the high-end side evaporator 24), and the remaining cold heat is stored in the high-end side heat storage evaporator 25 as heat storage to the heat storage medium 32. Is consumed.

  Further, the control device 33 controls the throttle amount of the high-side expansion valve 23 so that the refrigerant superheat degree at the outlet of the heat storage tank 31 (high-side heat storage evaporator 25 outlet) becomes a predetermined value (for example, about 2 ° C.). To do. Thereby, by the heat exchange between the cascade capacitor 30 and the heat storage tank 31, the refrigerant in the high-side refrigerant circuit at the outlet of the high-side heat storage evaporator 25 is completely evaporated and heat can be stored efficiently.

  In addition, the control device 33 controls the capacity of the high-end compressor 21 so that the evaporation temperature of the high-end evaporator 24 is lower than the temperature of the heat storage medium 32 by a predetermined temperature (for example, about 5 ° C.). Thereby, an appropriate temperature difference arises between the refrigerant temperature of the high-side refrigerant circuit passing through the high-side heat storage evaporator 25 and the temperature of the heat storage medium 32, and heat can be stored efficiently. At this time, the refrigerant in the low-side refrigerant circuit is completely condensed by the cascade capacitor 30 (low-side condenser 12) and substantially matches the temperature of the heat storage medium 32, so heat exchange is not performed. For this reason, the heat storage by the refrigerant | coolant of a high-source side refrigerant circuit can be performed efficiently.

<Cooling load: large>
When the cooling load is large (summer, daytime, etc.), a heat storage use operation mode is performed in which the low heat storage condenser 14 is cooled using the cold stored in the heat storage medium 32. In this heat storage use operation mode, the heat storage use operation for cooling the low-source-side heat storage condenser 14 by the cold heat stored in the heat storage medium 32 while performing the high-efficiency operation using the cascade capacitor 30 that directly exchanges heat between the refrigerants. Do. When the cooling load is large, the heat exchange amount of the cascade condenser 30 increases, so that the cooling capacity of the high-source side refrigerant circuit becomes insufficient compared to the cooling load. For this reason, the refrigerant in the low-side refrigerant circuit is not completely condensed in the cascade capacitor 30 (low-side condenser 12), and the remaining heat dissipation amount is caused by the cold storage heat of the heat storage medium 32 in the low-side heat storage condenser 14. To process.

  The control device 33 controls the throttle amount of the high-side expansion valve 23 so that the refrigerant superheat degree at the outlet of the cascade condenser 30 (high-side evaporator 24) becomes a predetermined value (for example, about 2 ° C.). As a result, the refrigerant in the high-end refrigerant circuit at the outlet of the cascade capacitor 30 is completely evaporated. As a result, the cooling capacity of the high-side refrigerant circuit can be output more reliably by the cascade capacitor 30.

  Further, the control device 33 controls the capacity of the high-side compressor 21 so that the evaporation temperature of the high-side evaporator 24 is substantially equal to the temperature of the heat storage medium 32. As a result, the refrigerant temperature of the high-side refrigerant circuit passing through the high-side heat storage evaporator 25 substantially matches the temperature of the heat storage medium 32, and heat exchange is performed between the refrigerant of the high-side refrigerant circuit and the heat storage medium 32. Not done. On the other hand, an appropriate temperature difference (for example, 5 ° C.) is generated between the low-side condensation temperature and the temperature of the heat storage medium 32, so that the heat can be efficiently used.

(Cooling load detection)
Here, an example of a method for detecting the cooling load will be described. As described above, the refrigeration capacity is determined for the cooling load, and the refrigerant flow rate is controlled by the low-side compressor 11 in order to obtain the required refrigeration capacity. That is, by outputting the required refrigeration capacity and keeping the low-side evaporation temperature constant, the temperature of the connected cooling target (for example, the interior temperature of the showcase) is kept constant. Specifically, if the cooling load increases, the temperature of the object to be cooled (internal temperature) rises and the low-side evaporation temperature rises. Therefore, the rotational speed of the low-side compressor 11 is increased, and a predetermined low Let it be the side evaporation temperature. If the cooling load is reduced, the low-side evaporation temperature is lowered. Therefore, the rotational speed of the low-side compressor 11 is decreased to a predetermined low-side evaporation temperature.

  For this reason, the cooling load can be determined by the rotational speed of the low-source compressor 11. Therefore, the control device 33 in the present embodiment detects the cooling load of the binary refrigeration apparatus from the rotational speed of the low-source compressor 11. And, by implementing the above heat storage operation mode, heat storage use operation mode, or normal operation mode according to the detected cooling load, it is possible to implement an appropriate operation mode according to the cooling load, enabling efficient operation It becomes.

  Specifically, the control device 33 determines that the cooling load is small when the cooling load is smaller than the first predetermined value, that is, when the rotational speed of the low-source compressor 11 is smaller than the first rotational speed. And implement the heat storage operation mode. Further, when the cooling load exceeds a second predetermined value that is larger than the first predetermined value, that is, when the rotational speed of the low-source compressor 11 exceeds the second rotational speed that is larger than the first rotational speed, cooling is performed. It is determined that the load is large, and the heat storage use operation mode is performed. When the cooling load exceeds the first predetermined value and is equal to or less than the second predetermined value, that is, when the rotation speed of the low-source compressor 11 exceeds the first rotation speed and is equal to or less than the second rotation speed, the cooling load is normal. It is determined that there is a normal operation mode.

  The method of detecting the cooling load is not limited to this, and the size of the cooling load may be determined based on the outside air temperature or the temperature of the cooling target. Further, for example, the operation mode may be switched on the basis of the time and time, such as nighttime, daytime, winter, and summer, assuming the magnitude of the cooling load.

(Operation of the low refrigeration cycle 10 when the high refrigeration cycle 20 is stopped)
The binary refrigeration apparatus in the present embodiment can start the operation of the low-source refrigeration cycle 10 regardless of the operating state of the high-source refrigeration cycle 20. That is, in the binary refrigeration apparatus of the present embodiment, the low-source refrigeration cycle 10 uses the cold energy stored in the heat storage tank 31, and therefore, after the low-source refrigeration cycle 10 is activated, the high-source refrigeration cycle 20 is activated. May be activated, may be activated from the operation of the high-source refrigeration cycle 20, or may be activated simultaneously.
Here, the operation when the operation of the low-source refrigeration cycle 10 is started when the high-source refrigeration cycle 20 is stopped will be described. In addition, when starting from the high original refrigerating cycle 20, or when starting simultaneously, it becomes the operation | movement mentioned above.

The low-source compressor 11 sucks CO ₂ refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the low-side condenser 12 (cascade capacitor 30). Since the high-source refrigeration cycle 20 is stopped, the low-source side condenser 12 does not sufficiently exchange heat with the refrigerant passing through the high-source refrigeration cycle 20, and the low-source side receiver in a high temperature / high pressure state. 13 (heat storage tank 31). When a CO ₂ refrigerant is used, it may flow into the low-source side receiver 13 in a supercritical state due to an increase in ambient temperature. The low source side liquid receiver 13 is cooled by the heat storage medium 32 accommodated in the heat storage tank 31, and the refrigerant flowing into the low source side liquid receiver 13 is cooled. Thereby, the pressure rise accompanying the temperature rise of a refrigerant | coolant is suppressed. The refrigerant that has flowed out of the low source side liquid receiver 13 flows into the low source side heat storage condenser 14 (heat storage tank 31). The low-source-side heat storage condenser 14 condenses the refrigerant by heat exchange with the heat storage medium 32 accommodated in the heat storage tank 31. The condensed and liquefied refrigerant passes through the low-side expansion valve 15. The low-side expansion valve 15 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the low-side evaporator 16. The low-source evaporator 16 evaporates the refrigerant by exchanging heat with the object to be cooled. The high-end compressor 21 sucks the CO ₂ refrigerant that has been vaporized.

  Thus, the binary refrigeration apparatus in the present embodiment uses the cold energy stored in the heat storage tank 31 so that the operation of the low-source refrigeration cycle 10 can be started regardless of the operating state of the high-source refrigeration cycle 20. Is possible.

  In a conventional dual refrigeration system, the low refrigeration cycle and the high refrigeration cycle are assembled together via a cascade capacitor, and the low refrigeration cycle must be operated simultaneously. I must. On the other hand, as described above, the binary refrigeration apparatus in the present embodiment can operate the low refrigeration cycle 10 regardless of the operating state of the high refrigeration cycle 20, and the independence of the operation of each refrigeration cycle. It is possible to promote device design of each refrigeration cycle, installation capacity independence and service independence.

  In addition, since the binary refrigeration apparatus in the present embodiment includes the heat storage tank 31, the capacity of the high-source refrigeration cycle 20 (refrigeration capacity) and the capacity of the low-source refrigeration cycle 10 (refrigeration capacity) are integrated. The sex becomes unnecessary. For example, even if the capacity of the high-source refrigeration cycle 20 is less than or equal to the capacity of the low-source refrigeration cycle 10, the load consistency between the high-source side and the low-source side can be achieved by considering the operation time.

  That is, the high-source refrigeration is performed so that the value obtained by multiplying the refrigeration capacity of the high-source refrigeration cycle 20 by the operation time is equal to or greater than the value obtained by multiplying the refrigeration capacity of the low-source refrigeration cycle 10 by the operation time so as to satisfy the following formula. Control for starting or stopping the operation of the cycle 20 and the low-source refrigeration cycle 10 is performed.

  Refrigeration capacity of the high refrigeration cycle x operation time ≥ Refrigeration capacity of the low refrigeration cycle x operation time

The refrigeration capacity of each refrigeration cycle can be obtained by using a known calculation method. For example, it can be calculated by calculation using the output of the compressor and the enthalpy converted from the refrigerant temperature and pressure.
The control device 33 sequentially calculates the refrigeration capacity of each refrigeration cycle and multiplies the operation time. And control which starts or stops operation of high original refrigeration cycle 20 and low original refrigeration cycle 10 is performed so that the above-mentioned formula may be satisfied. For example, after the heat storage operation by the high-source refrigeration cycle 20 is performed, when the high-source refrigeration cycle 20 is stopped and only the low-source refrigeration cycle 10 is operated, when the right side of the above formula becomes larger than the left side, the control device 33 Starts the operation of the high refrigeration cycle 20 and controls to satisfy the above equation.

  As described above, in the present embodiment, the low-source refrigeration cycle 10 can be operated regardless of the operating state of the high-source refrigeration cycle 20. That is, starting from the low-source refrigeration cycle 10, starting from the high-source refrigeration cycle 20, or each refrigeration cycle may be started simultaneously. In particular, when starting from the low-source refrigeration cycle 10 connected to the load device, for example, the load device such as a showcase performs cooling immediately after the start-up, so that rapid cooling is possible, which is suitable for user requests.

  In the present embodiment, it is possible to perform a heat storage operation or a heat storage use operation while performing a high-efficiency operation by the cascade capacitor 30 in response to a change in cooling load. Further, high efficiency operation can be achieved in normal operation other than heat storage, and cooling load leveling by heat storage operation can also be realized. Therefore, it is possible to save energy at all times, and it is possible to achieve further energy saving because it is possible to reduce the amount of electric power used by cooling load leveling by heat storage operation and to stably operate at an operating point with high efficiency.

Embodiment 3 FIG.
FIG. 3 is a refrigerant circuit diagram of the binary refrigeration apparatus according to Embodiment 3 of the present invention. In FIG. 3, in addition to the configuration of the second embodiment, the high-source refrigeration cycle 20 includes a high-source side heat storage bypass pipe 26 that bypasses the high-source side heat storage evaporator 25, and the low-source refrigeration cycle 10 includes a low-source refrigeration cycle 10. A low-source side heat storage bypass pipe 17 that bypasses the side heat storage condenser 14 is provided.

  The high-source side heat storage bypass pipe 26 is provided with an on-off valve that shuts off or opens the refrigerant flow path. By shutting off or opening this on-off valve, the refrigerant flowing out of the high-end side evaporator 24 The flow path leading to the high-end side compressor 21 via the main-side heat storage evaporator 25 and the flow path leading to the high-end side compressor 21 by bypassing the high-end side heat storage evaporator 25 are switched. Further, the low-side heat storage bypass pipe 17 is provided with an on-off valve that shuts off or opens the refrigerant flow path. By shutting off or opening this on-off valve, the refrigerant that has flowed out of the low-side condenser 12 is discharged. The flow path leading to the low-source side expansion valve 15 via the low-element side heat storage condenser 14 and the flow path leading to the low-element side heat storage condenser 14 and bypassing the low-element side heat storage condenser 14 are switched.

  Further, the high-source refrigeration cycle 20 includes a high-source side heat storage expansion valve 27 upstream of the high-source side heat storage evaporator 25, that is, between the high-source side evaporator 24 and the high-source side heat storage evaporator 25. ing. The high-side heat storage expansion valve 27 decompresses the refrigerant flowing out from the high-side evaporator 24 and expands it. For example, an arbitrary pressure reducing device such as a flow rate control means such as an electronic expansion valve, a throttling device or the like is used.

With this configuration, in the present embodiment, in the high-side refrigerant circuit, in the normal operation mode in which heat storage and utilization to the heat storage medium 32 are not performed, the flow path of the high-side heat storage bypass pipe 26 is opened. The piping connected to the heat storage tank 31 is cut off. For this reason, in the normal operation mode, the cooling capacity can be surely output by the cascade capacitor 30, and furthermore, no heat exchange is performed in the heat storage tank 31, so that highly efficient operation can be performed.
Moreover, at the time of the heat storage operation mode in which heat storage is performed, the flow path of the high-source side heat storage bypass pipe 26 is shut off, and the pipe connected to the one heat storage tank 31 is opened. In this case, the operation is the same as that of the second embodiment described above.

  Moreover, in this Embodiment, the high-source side thermal storage expansion valve 27 is installed. For this reason, it becomes possible to independently control the evaporation temperature of the refrigerant in the high-side refrigerant circuit flowing into the heat storage tank 31. For this reason, it can be reliably set as the evaporation temperature required for heat storage irrespective of the driving | operation operation | movement of the said binary refrigeration apparatus. Moreover, when the high-source side heat storage bypass pipe 26 is installed, similarly, the refrigerant flow rate necessary for heat storage, that is, the cold storage capacity can be ensured regardless of the operation of the refrigeration apparatus.

In the low operation side refrigerant circuit, in the normal operation mode in which the heat storage medium 32 is not stored and used, the flow path of the low supply side heat storage bypass pipe 17 is opened, and the pipe connected to the one heat storage tank 31 is shut off. For this reason, in the normal operation mode, it is possible to reliably condense and condense in the cascade condenser 30, and furthermore, since heat exchange is not performed in the heat storage tank 31, highly efficient operation can be performed.
Moreover, at the time of the heat storage operation mode in which heat storage is performed, the flow path of the low-source side heat storage bypass pipe 17 is shut off, and the pipe connected to one heat storage tank 31 is opened. In this case, the operation is the same as that of the second embodiment described above.

  In the binary refrigeration apparatus in the first to third embodiments, for example, when a showcase or the like is a cooling target, it is assumed that the low source side evaporation temperature is used at −10 ° C. to −40 ° C. At this time, the high-side evaporation temperature at which the operation efficiency of the binary refrigeration apparatus is optimal is a temperature of −10 ° C. or higher and 10 ° C. or lower. As the heat storage medium 32 that can use the heat storage in this temperature range, for example, ice whose phase changes at 0 ° C. is an optimal medium.

  The binary refrigeration apparatus of the present invention can be widely applied to refrigeration and refrigeration equipment such as showcases, commercial refrigeration refrigerators, and vending machines that require non-CFC refrigerants, CFC refrigerant reduction, and equipment energy saving.

  10 Low-source refrigeration cycle, 11 Low-source side compressor, 12 Low-source side condenser, 13 Low-source-side receiver, 14 Low-source-side heat storage condenser, 15 Low-source-side expansion valve, 16 Low-source-side evaporator, 17 Low original side heat storage bypass pipe, 20 High original refrigeration cycle, 21 High original side compressor, 22 High original side condenser, 23 High original side expansion valve, 24 High original side evaporator, 25 High original side heat storage evaporator, 26 high-side heat storage bypass pipe, 27 high-side heat storage expansion valve, 30 cascade condenser, 31 heat storage tank, 32 heat storage medium, 33 control device.

Claims (6)

A first refrigerant circuit that connects the first compressor, the first condenser, the first expansion device, the first evaporator, and the first heat storage evaporator, and circulates the refrigerant;
A second refrigerant circuit that connects the second compressor, the second condenser, the liquid receiver, the second throttling device, and the second evaporator, and circulates the refrigerant;
A cascade condenser configured by the first evaporator and the second condenser, wherein the refrigerant flowing through the first evaporator and the refrigerant flowing through the second condenser exchange heat;
The first heat storage evaporator and the liquid receiver are accommodated, the heat storage medium is cooled by the first heat storage evaporator to store cold energy, and the liquid receiver is cooled by the cold heat stored in the heat storage medium. A two-stage refrigeration apparatus comprising a heat storage tank. The second refrigerant circuit includes a second heat storage condenser between the liquid receiver and the second expansion device,
2. The binary refrigeration apparatus according to claim 1, wherein the heat storage tank accommodates the second heat storage condenser and cools the second heat storage condenser by cold energy stored in the heat storage medium. The binary refrigeration apparatus according to claim 1 or 2, wherein the operation of the second refrigerant circuit can be started regardless of the operation state of the first refrigerant circuit. The binary refrigeration apparatus according to any one of claims 1 to 3, wherein the operation of the first refrigerant circuit is activated after the operation of the second refrigerant circuit is activated. A value obtained by multiplying the refrigeration capacity of the first refrigerant circuit by the operation time of the first refrigerant circuit is equal to or greater than a value obtained by multiplying the refrigeration capacity of the second refrigerant circuit and the operation time of the second refrigerant circuit. In addition,
The binary refrigeration apparatus according to any one of claims 1 to 4, wherein the operation of the first and second refrigerant circuits is started or stopped. The binary refrigeration apparatus according to any one of claims 1 to 5, wherein carbon dioxide is used as the refrigerant in the second refrigerant circuit.

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