Defrosting a heat exchanger in a heat pump by diverting warm refrigerant to an exhaust header

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.

主权项

1. A heat pump having an improved defrost cycle, the heat pump comprising:
a compressor; at least one expansion device; a first heat exchanger comprising:
a first header;a second header; andmultiple cross tubes extending from the first header to the second header, wherein:
each of the multiple cross tubes connects to the first header;each of the multiple cross tubes connects to the second header;the first header is parallel to the second header;the multiple cross tubes are parallel to each other; and the multiple cross tubes each include multiple contiguous parallel refrigerant passageways therethrough;multiple fins between the cross tubes wherein the fins are bonded to the cross tubes;at least one first connection point to the first heat exchanger where refrigerant is delivered to the first heat exchanger from the compressor during the defrost cycle;a second connection point to the first heat exchanger where refrigerant exits the first heat exchanger during the defrost cycle; anda third connection point to the first heat exchanger where refrigerant is delivered from the compressor to the first heat exchanger during at least part of the defrost cycle; a first refrigerant conduit connecting a discharge port on the compressor to the at least one first connection point of the first heat exchanger; a second refrigerant conduit connecting the second connection point of the first heat exchanger to the at least one expansion device; a third refrigerant conduit connecting the first refrigerant conduit to the third connection point of the first heat exchanger; a defrost valve located in the third refrigerant conduit between the first refrigerant conduit and the third connection point of the first heat exchanger, wherein, when the defrost valve is closed, refrigerant flow through the third refrigerant conduit is blocked; and a control system that controls the defrost valve and opens the defrost valve during the defrost cycle allowing refrigerant to flow through the third refrigerant conduit to the third connection point to the first heat exchanger; wherein:
the first connection point to the first heat exchanger is at the first header;the second connection point to the first heat exchanger is at the second header;the third connection point to the first heat exchanger is at the second header;refrigerant that, during at least part of the defrost cycle, passes through the third refrigerant conduit, through the defrost valve, and through the third connection point to the first heat exchanger, passes through the second header, heating the second header between the third connection point to the first heat exchanger and the second connection point to the first heat exchanger without passing through any cross tubes of the first heat exchanger;the control system comprises a digital controller comprising programming instructions to open the defrost valve during the defrost cycle to defrost the first heat exchanger between the third connection point and the second connection point; andthe digital controller further comprises programming instructions to keep the defrost valve closed when the heat pump is not in the defrost cycle.