evaporator system for protection against frost and heat pumps to absorb heat from the ambient air

摘要

A heat pump has its evaporator placed inside a duct through which ambient air circulates either naturally or by forced draught from a fan. The evaporator is built in two separate stages which are in series with each other and have a second expansion valve between them. The first expansion valve is upstream of the first stage of the evaporator. The expansion valves are regulated so that the temperature of the first stage is sufficient to condense moisture in the air but not to freeze it. The condensed moisture is collected in a drain pan and run off as liquid. The temperature of the second stage can be below freezing point without any risk of icing on the evaporator.