INNOVATIVE TECHNICAL DESIGN OF AIR HEAT PUMPS OPERATING IN THE CONDITIONS OF THE NORTHERN CLIMATE

Abstract

Air source heat pumps are widely used for residential and commercial heating because of their relatively low installation costs, much lower than for geothermal pumps. However, they have certain disadvantages, causing limitations in their use, namely low COP and further, its considerable decrease as the discharge temperature of the compressor increases and the outdoor temperature decreases. Very often this leads to expensive, two-stage compressor systems or to backup heating. This paper describes the calculations and investigations to adapt an ejector cycle for air-source heat pump designed for operation in Northern climate, where outdoor temperature may drop to –30C. The ejector was installed on compressor intake to increase the suction pressure and to lower the compression ratio. The objective of this research was to permit a single-stage compression heat pump to work at outdoor temperatures below –18C, thus avoiding more complicated two-step compression at such conditions.