24 June 2014

Air-source heat pumps with refrigerant mixtures for cold climates

Heat pumps represent the only end-use heating technology that has coefficient of performance greater than one. However, the efficiency of air-source heat pumps decreases
drastically at low cold source temperature which represents a higher barrier to their adoption in cold climates. The use of mixtures of refrigerants with the aim of increasing the COP and heating capacity at lower temperatures by taking advantage of the thermal glide is an option
that has been little studied so far. The main goal of the present study is to find a refrigerant mixture properly selected so that it enables good heating performance at low temperatures. This mixture must have desirable thermophysical properties but also it must be non-toxic,
non-flammable, oil soluble, and have low GWP. Currently, there is no acceptable pure refrigerant that satisfies all these requirements. In this paper we will present a methodology
used for selecting appropriate mixtures, preliminary results, and potential gains for cold climate heat pumps.