Refrigeration apparatus

Abstract

A refrigeration apparatus uses supercritical range refrigerant, and includes a multi-stage compression mechanism, a heat source-side heat exchanger, a usage-side heat exchanger, a switching mechanism switchable between cooling and heating operation states, an intermediate heat exchanger integrated with the heat source-side heat exchanger, and an intermediate heat exchanger bypass tube connected to the intermediate refrigerant tube so as to bypass the intermediate heat exchanger. The intermediate heat exchanger is connected to an intermediate refrigerant tube to draw refrigerant discharged from the first-stage compression element into the second-stage compression element, and functions as a cooler of the refrigerant discharged from the first-stage compression element and drawn into the second-stage compression element. The intermediate heat exchanger bypass tube ensures that refrigerant does not flow to the intermediate heat exchanger when a reverse cycle defrosting operation is performed.

Description

TECHNICAL FIELD[0001]The present invention relates to a refrigeration apparatus, and particularly relates to a refrigeration apparatus which has a refrigerant circuit configured to be capable of switching between a cooling operation and a heating operation and which performs a multistage compression refrigeration cycle by using a refrigerant that operates in a supercritical range.BACKGROUND ART[0002]As one conventional example of a refrigeration apparatus which has a refrigerant circuit configured to be capable of switching between a cooling operation and a heating operation and which performs a multistage compression refrigeration cycle by using a refrigerant that operates in a supercritical range, Patent Document 1 discloses an air-conditioning apparatus which has a refrigerant circuit configured to be capable of switching between an air-cooling operation and an air-warming operation and which performs a two-stage compression refrigeration cycle by using carbon dioxide as a refrig...

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Benefits of technology

[0007]As a countermeasure to this problem, the intermediate heat exchanger which functions as a cooler of the refrigerant discharged from the first-stage compression element and drawn into the second-stage compression element is provided to the intermediate refrigerant tube for drawing refrigerant discharged from the first-stage compression element into the second-stage compression element, the intermediate heat exchanger bypass tube is connected to the intermediate refrigerant tube so as to bypass the intermediate heat exchanger, the intermediate heat exchanger bypass tube is used to ensure that the intermediate heat exchanger functions as a cooler when the switching mechanism corresponding to the aforementioned four-way switching valve is set to a cooling operation state corresponding to the air-cooling operation, and also that the intermediate heat exchanger does not function as a cooler when the switching mechanism is set to a heating operation state corresponding to the air-warming operation. This minimizes the temperature of the refrigerant discharged from the compression mechanism corresponding to the aforementioned compressor during the cooling operation, suppresses heat radiation from the intermediate heat exchanger to the exterior during the heating operation, and prevents loss of operating efficiency.

[0010]In view of this, in the refrigeration apparatus according to a first aspect of the present invention, an intermediate heat exchanger is disposed above a heat source-side heat exchanger. Thereby, in this refrigeration apparatus, frost deposits are minimized in the border between the intermediate heat exchanger and the heat source-side heat exchanger regardless of the intermediate heat exchanger being integrated with the heat source-side heat exchanger, and unlike cases in which the intermediate heat exchanger is disposed below the heat source-side heat exchanger, there is less risk that water that has melted and dripped down from the heat source-side heat exchanger due to the defrosting of the heat source-side heat exchanger will adhere, freeze, and spread on the intermediate heat exchanger, and the intermediate heat exchanger therefore does not need to be defrosted when the reverse cycle defrosting operation is performed. In this refrigeration apparatus, taking advantage of the fact that the intermediate heat exchanger does not need to be defrosted during the reverse cycle defrosting operation, when the reverse cycle defrosting operation is performed, the intermediate heat exchanger bypass tube is used to ensure that the refrigerant does not flow to the intermediate heat exchanger, thereby preventing heat from being radiated from the intermediate heat exchanger to the exterior and minimizing the decrease in the defrosting capacity of the heat source-side heat exchanger when the reverse cycle defrosting operation is performed.

[0011]The reverse cycle defrosting operation can thereby be performed efficiently in this refrigeration apparatus.

[0014]In view of this, in this refrigeration apparatus, when the reverse cycle defrosting operation is performed, the second-stage injection tube is used to ensure that the refrigerant fed from the heat source-side heat exchanger to the usage-side heat exchanger is returned to the second-stage compression element, whereby the flow rate of the refrigerant flowing through the usage-side heat exchanger can be reduced, and the flow rate of the refrigerant flowing through the heat source-side heat exchanger can be guaranteed.

[0015]It is thereby possible in this refrigeration apparatus to minimize the temperature decrease on the usage side and to reduce the defrosting time of the heat source-side heat exchanger when the reverse cycle defrosting operation is performed.

Problems solved by technology

As a result, since the refrigerant discharged from the second-stage compression element of the compressor has a high temperature, there is a large difference in temperature between the refrigerant and the water or air as a cooling source in the outdoor heat exchanger functioning as a refrigerant cooler, and the outdoor heat exchanger has much heat radiation loss, which poses a problem in making it difficult to achieve a high operating efficiency.

Moreover, there is a danger that frost deposits will occur in the intermediate heat exchanger as well because a heat exchanger whose heat source is air is used as the intermediate heat exchanger and the intermediate heat exchanger is integrated with the heat source-side heat exchanger; in this case, refrigerant must be passed through not only the heat source-side heat exchanger but also the intermediate heat exchanger and the intermediate heat exchanger must be defrosted.

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