Experimental evaluation of a water based high temperature heat pump with novel high pressure lift turbo compressors

This paper evaluates a water based (R718) high temperature heat pump with novel high-pressure lift turbo compressors. The first stage turbo compressor is designed for steam compression and the second stage is designed for air, both are based on economic standard components from the automotive industry. A 500 kW compressor test rig was built by SINTEF to test the 2-stage configuration in superheated steam conditions. Compressor efficiency and system COP was calculated based on measurements from the test rig. Also, compressor maps for the two compressors was created. For the 1st stage compressor, the maximum isentropic efficiency was 67% and maximum pressure ratio 2.4. The second stage yielded 77% and 2.0. The two-stage configuration was able to produce 4.23 bar steam, from atmospheric inlet conditions. The system COP corresponded to 4.5 and a Carnot efficiency of 49.5 %.