Refrigerating Apparatus and Air Conditioner

Abstract

An air conditioner has a refrigerant circuit and a first oil returning circuit. The refrigerant circuit has a plurality of utilization refrigerant circuits each having a utilization heat exchanger and a utilization expansion valve connected to a heat source refrigerant circuit that includes a compression mechanism, a heat source expansion valve and a heat source heat exchanger configured so that a refrigerant flows in from below and flows out from above when the heat source heat exchanger functions as an evaporator. The heat source refrigerant circuit uses a combination of a refrigerating machine oil and a refrigerant that does not separate into two layers in a temperature range of 30° C. or below. The first oil returning circuit is connected to a lower portion of the heat source heat exchanger and returns the refrigerating machine oil accumulated inside the heat source heat exchanger to the compression mechanism together with the refrigerant.

Description

TECHNICAL FIELD [0001] The present invention relates to a refrigerating apparatus and an air conditioner, and particularly relates to a refrigerating apparatus and an air conditioner provided with a refrigerant circuit that has an evaporator configured so that refrigerant flows in from below and flows out from above. BACKGROUND ART [0002] Conventionally, there has been a refrigerating apparatus disposed with a vapor compression-type refrigerant circuit including a heat exchanger configured such that refrigerant flows in from below and flows out from above as an evaporator of the refrigerant (e.g., see Patent Document 1). In order to prevent refrigerating machine oil from accumulating inside the evaporator, the refrigerating apparatus is configured to extract, from the vicinity of the surface of the refrigerant, the refrigerating machine oil accumulating in a state where it floats on the surface of the refrigerant as a result of the refrigerating machine oil and the refrigerant separ...

AI Technical Summary

Benefits of technology

[0013] Further, in the aforementioned air conditioner, when a pressurizing circuit is disposed in the refrigerant circuit to cause the high-pressure gas refrigerant compressed by the compressor to merge with the refrigerant whose pressure has been reduced in the heat source expansion valve and which is sent to the utilization refrigerant circuits when the heat source heat exchangers are caused to function as condensers of the refrigerant, the refrigerant sent from the heat source expansion valve to the utilization refrigerant circuits becomes a gas-liquid two-phase flow. Moreover, the gas fraction of the refrigerant after the high-pressure gas refrigerant has merged therewith from the pressurizing circuit becomes larger the more the openings of the heat source expansion valves are reduced, and drift arises between the plural utilization refrigerant circuits, resulting in the problem that the openings of the heat source expansion valves cannot be sufficiently reduced. As a result, similar to when the heat source heat exchangers are caused to function as evaporators of the refrigerant, when plural heat source heat exchangers are disposed in the heat source refrigerant circuit and the overall air conditioning load of the plural utilization refrigerant circuits becomes extremely small, it becomes necessary to conduct control to reduce the condensing ability by closing the plural heat source expansion valves to reduce the number of heat source heat exchangers functioning as evaporators or to reduce the condensing ability by causing some of the plural heat source heat exchangers to function as evaporators to offset the condensing ability of the heat source heat exchangers functioning as condensers.

[0053] Thus, because simplification of the heat source heat exchanger becomes possible in an air conditioner where simplification of the heat source heat exchangers could not be realized by restricting the control width of the control of the evaporating ability of the heat source heat exchangers, increases in the number of parts and cost that had occurred in conventional air conditioners as a result of disposing plural heat source heat exchangers can be prevented. Further, the problem of the COP becoming poor can be eliminated in an operating condition where, when some of the heat source heat exchangers are caused to function as condensers to reduce the evaporating ability, the amount of refrigerant compressed in the compression mechanism increases in correspondence to the amount of refrigerant condensed by the heat source heat exchangers and the air conditioning load of the entire plurality of utilization refrigerant circuits is small.

Problems solved by technology

However, even if one tries to reduce the amount of refrigerant flowing through the heat source heat exchangers by reducing the openings of the heat source expansion valves when the heat source heating exchangers are caused to function as evaporators with little evaporating ability, such as when the air conditioning load in the plural utilization refrigerant circuits becomes extremely small, the evaporating ability cannot be sufficiently controlled just by regulating the openings of the heat source expansion valves because the openings of the heat source expansion valves cannot be reduced that much due to the restriction of the level of the refrigerant inside the heat source heat exchangers.

For this reason, there are the problems that increases in the number of parts and cost arise as a result of disposing plural heat source heat exchangers, the amount of the refrigerant compressed in the compressor increases in correspondence to the amount of refrigerant condensed by the heat source heat exchangers when some of the plural heat source heat exchangers are caused to function as condensers to reduce the evaporating ability, and the COP becomes poor in an operating condition where the overall air conditioning load of the plural utilization refrigerant circuits is small.

Moreover, the gas fraction of the refrigerant after the high-pressure gas refrigerant has merged therewith from the pressurizing circuit becomes larger the more the openings of the heat source expansion valves are reduced, and drift arises between the plural utilization refrigerant circuits, resulting in the problem that the openings of the heat source expansion valves cannot be sufficiently reduced.

For this reason, there are the problems that increases in the number of parts and cost arise as a result of disposing plural heat source heat exchangers, the amount of the refrigerant compressed in the compressor increases in correspondence to the amount of refrigerant evaporated by the heat source heat exchangers when some of the plural heat source heat exchangers are caused to function as evaporators to reduce the condensing ability, and the COP becomes poor in an operating condition where the overall air conditioning load of the plural utilization refrigerant circuits is small.

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