First experimental results of a R744 water-to-water heat pump for space heating.

The transition towards more sustainable and energy-efficient heating technologies is crucial to mitigate climate change effects. Natural refrigerants have gained attention as environmentally friendly alternatives to traditional refrigerants. CO2 (R744) is a valid alternative because it is both non-toxic and non-flammable and has a low global warming potential. In the present paper, the first findings of an experimental analysis carried out to evaluate the performance of a water-to-water heat pump using R744 as a refrigerant are presented. The heat pump is equipped with a semi-hermetic variable speed compressor, three brazed plate heat exchangers, and an electronic expansion valve to control and optimize the pressure at the gas cooler. The heat pump is tested under various conditions to supply hot water with high ΔT for space heating. The results indicate that the heating capacity ranges from 5.6 kW to around 7.2 kW, and the COP ranges from 2.89 to 4.73.