| 摘要 |
Heat pumps with improved defrost cycles and methods of defrosting heat exchangers, for example, having microchannel outdoor heat exchangers. A heat exchanger has three types of connection points that are used during a defrost cycle. Two connection points are used to deliver hot refrigerant gas to the heat exchanger and one connection point is where refrigerant exits the heat exchanger. Two of the connection points are at the same header and during at least part of the defrost cycle, at least part of the hot refrigerant gas is passed through that header without passing through any cross tubes of the heat exchanger. A defrost valve in a refrigerant conduit opens during the defrost cycle to deliver hot refrigerant gas to the connection point on the header. In a number of embodiments, the defrost valve is open only during a portion of the defrost cycle. |
