Heat pump apparatus

Patent metadata

Field	Value
Publication number	US-9557085-B2
Application number	US-201013384680-A
Country	US
Kind code	B2
Filing date	Jan 15, 2010
Priority date	Jul 22, 2009
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

In a heat pump apparatus, it is aimed to enhance efficiency of a defrost operation by reducing a loss of heat radiation during the defrost operation and reducing a compressor input during the defrost operation. The heat pump apparatus includes a main refrigerant circuit in which a compressor, a first heat exchanger, an expansion mechanism, and a second heat exchanger are connected sequentially, and also includes a bypass circuit including an on-off valve and providing a connection by bypassing the expansion mechanism. The main refrigerant circuit includes a four-way valve that switches between a heating operation and the defrost operation by switching an order in which the refrigerant circulates through the main refrigerant circuit. The main refrigerant circuit also includes a first temperature detection unit and a second temperature detection unit. Based on values detected by these temperature detection units, a degree of superheat of the first heat exchanger during the defrost operation is computed. When the heating operation is switched to the defrost operation, the heat pump apparatus increases a circulation amount of the refrigerant circulating through the refrigerant circuit by opening the on-off valve, and also controls an operation frequency of the compressor such that the degree of superheat is at a predetermined target value.

First claim

The invention claimed is:

1. A heat pump apparatus comprising:
a refrigerant circuit in which a compressor, a first heat exchanger, a first expansion mechanism, a liquid accumulator, a second expansion mechanism, and a second heat exchanger are connected sequentially;
a bypass circuit that includes an on-off valve, and connects a midpoint between the first heat exchanger and the first expansion mechanism with a midpoint between the second expansion mechanism and the second heat exchanger in the refrigerant circuit such that the first expansion mechanism, the liquid accumulator, and the second expansion mechanism are bypassed,
a switching unit that switches a direction in which a refrigerant flows between a heating operation and a defrost operation, thereby switching between the heating operation and the defrost operation;
a superheat detection unit that detects a degree of superheat of the refrigerant at the first heat exchanger during the defrost operation; and
a control unit that, when the heating operation is switched to the defrost operation by the switching unit, closes the second expansion mechanism, and after a predetermined period of time has elapsed, closes the first expansion mechanism and opens the on-off valve included in the bypass circuit, thereby increasing a circulation amount of the refrigerant circulating through the refrigerant circuit, and controls an operating frequency of the compressor such that the degree of superheat detected by the superheat detection unit is at a target value which is predetermined.

2. The heat pump apparatus of claim 1 ,
wherein the control unit changes the target value depending on a heating load which is a quantity of heat required for heating.

3. The heat pump apparatus of claim 2 ,
wherein the control unit sets the target value such that the target value when the heating load is smaller than a predetermined value is larger compared to the target value when the heating load is greater than the predetermined value, so that the operating frequency of the compressor is lower when the heating load is smaller than the predetermined value compared to when the heating load is greater than the predetermined value.

4. The heat pump apparatus of claim 2 , further comprising:
a compressor frequency detection unit that detects a total number of revolutions of the compressor during the heating operation; and
a time measurement unit that measures a heating operation time,
wherein the control unit computes the heating load from a value obtained by dividing the total number of revolutions of the compressor during the heating operation detected by the compressor frequency detection unit by the heating operation time measured by the time measurement unit.

5. The heat pump apparatus of claim 1 ,
wherein the control unit, when the defrost operation is switched to the heating operation, closes the on-off valve included in the bypass circuit and opens the first expansion mechanism and the second expansion mechanism, and after a predetermined period of time has elapsed, switches the direction in which the refrigerant flows by the switching unit.

Assignees

• Hamada Mamoru
• Unezaki Fumitake
• Takahashi Yoshihiro
• Takahashi Kengo
• Okada Kazuki
• Minamisako Hirokazu
• Uchino Shinichi
• Mitsubishi Electric Corp

Inventors

• Hamada Mamoru
• Unezaki Fumitake
• Takahashi Yoshihiro
• Takahashi Kengo
• Okada Kazuki
• Minamisako Hirokazu
• Uchino Shinichi

Classifications

• F25B2600/021

  Inverters therefor · CPC title

• F25B2700/21151

  at the suction side of the compressor · CPC title

• F25B2600/2513

  Expansion valves · CPC title

• F24F2011/0087

  Mechanical Engineering · mapped topic

• F25B2600/2501

  Bypass valves · CPC title