The experimental analysis of the effect of ambient factors on the defrosting of economised vapour injection compressor air source heat pump in marine climates

Air source heat pumps have numerous advantages in many applications over other heating equipment in marine climates with regard to energy efficiency. The main concerns are based around maintaining a sufficiently high seasonal coefficient of performance (COP) when (a) utilising cold air as a heat source and (b) delivering hot water to a residential heating circuit originally designed for water temperatures of 60 °C or more with oil heating. The economised vapour injection (EVI) compressor has the capability of overcoming some of the difficulties of high temperature lift operation during cold ambient conditions. However it is not clear except ambient temperature how the other ambient factors may affect the performance of EVI air-source heat pump in marine climates. This paper evaluates operating performance with the defrost effect for a retrofit residential EVI air-source heat pump in Belfast, UK. The ambient factors, which affect the performance of the heat pump defrosting, were studied. The investigation was to optimise the operation of an EVI air source heat pump operating under defrost conditions encountered in maritime climates.