Refrigeration System

Abstract

A refrigerant circuit (20) includes a low stage compressor (101, 102, 121, 122), a high stage compressor (41, 42, 43), an outdoor heat exchanger (44) and a utilization side heat exchanger (83, 93). During a defrosting operation of the refrigeration system (10), the high stage compressor (41, 42, 43) is driven. Refrigerant discharged from the high stage compressor (41, 42, 43) is pumped into the utilization side heat exchanger (83, 93) to heat frost on it from its inside. Thereafter, the refrigerant evaporates in the outdoor heat exchanger (44), is then compressed by the high stage compressor (41, 42, 43) and is sent again to the utilization side heat exchanger (83, 93).

Description

TECHNICAL FIELD[0001]This invention relates to refrigeration systems operating in a two-stage compression refrigeration cycle and particularly relates to techniques for defrosting a utilization side heat exchanger for cooling the internal air in a freezer or the like.BACKGROUND ART[0002]Refrigeration systems are conventionally known that include a refrigerant circuit operating in a refrigeration cycle and they are widely used as cooling machines for chillers or freezers for storing food and other materials.[0003]For example, Patent Document 1 discloses a refrigeration system for cooling the internal air of a freezer such as in a convenience store. Connected in the refrigerant circuit of this refrigeration system are a low stage compressor, a high stage compressor, an outdoor heat exchanger (heat-source side heat exchanger) and a cooling heat exchanger (utilization side heat exchanger). This refrigeration system operates in a so-called two-stage compression refrigeration cycle in whi...

AI Technical Summary

Benefits of technology

[0039]According to the present invention, during the defrosting operation, frost adhering to the surface of the utilization side heat exchanger (83, 93) is heated from the inside of the utilization side heat exchanger (83, 93) by feeding the refrigerant discharged by the high stage compressor (41, 42, 43) into the utilization side heat exchanger (83, 93). Therefore, the utilization side heat exchanger (83, 93) can be effectively defrosted, which reduces the time taken to defrost it.

[0040]Furthermore, according to the present invention, since during the defrosting operation the heat-source side heat exchanger (44) serves as an evaporator, heat given from air to refrigerant can be used to defrost the utilization side heat exchanger (83, 93). In other words, according the present invention, heat given to refrigerant by the high stage compressor (41, 42, 43) and heat given to refrigerant by the heat-source side heat exchanger (44) are both used to defrost the utilization side heat exchanger (83, 93). This reduces the defrosting time and in turn reduces the power consumption of the refrigeration system during the defrosting operation.

[0041]Particularly, since in the second aspect of the invention the defrosting operation is carried out with the low stage compressor (101, 102, 121, 122) off, this reduces the operating power during the defrosting operation.

[0042]Furthermore, according to the third aspect of the invention, by opening and closing the shut-off valve (SV-2, SV-4) of the bypass pipe (119, 139), the refrigeration system can easily switch between the cooling operation of compressing refrigerant evaporated by the utilization side heat exchanger (83, 93) in two stages, i.e., in the low stage compressor (101, 102, 121, 122) and the high stage compressor (41, 42, 43), and the defrosting operation of allowing refrigerant discharged from the high stage compressor (41, 42, 43) to bypass the low stage compressor (101, 102, 121, 22) and sending the refrigerant to the utilization side heat exchanger (83, 93).

[0043]Furthermore, in the fourth aspect of the invention, during the cooling operation, refrigerant condensed in the heat-source side heat exchanger (44) is allowed to flow through the drain pan heating pipes (81, 91) before being reduced in pressure by the utilization side expansion valve (82, 92). Therefore, according to this aspect of the invention, heat of condensation of refrigerant can be used to melt frost and ice blocks in the drain pan (85, 95) and the water thus obtained can be promptly drained as drainage away from the drain pan (85, 95). Furthermore, the refrigerant flowing through the drain pan heating pipe (81, 91) gives heat to frost and ice blocks in the drain pan (85, 95) and thereby gradually increases its degree of supercooling. Therefore, the enthalpy of refrigerant flowing into the utilization side heat exchanger (83, 93) can be reduced, which increases the air cooling effect of the utilization side heat exchanger (83, 93).

[0044]Furthermore, in the fifth aspect of the invention, during the defrosting operation, the refrigerant used to defrost the utilization side heat exchanger (83, 93) is sent, without reducing its pressure with the utilization side expansion valve (82, 92), to the drain pan heating pipe (81, 91). Therefore, according to this aspect of the invention, also during the defrosting operation, heat of refrigerant flowing through the drain pan heating pipe (81, 91) can be used to melt frost and ice blocks in the drain pan (85, 95).

Problems solved by technology

This causes a problem that moisture in the air adheres to the cooling heat exchanger and freezes on it and the frost on it prevents the cooling of the internal air in the freezer.

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