Experimental investigation of a Thermally Driven Heat Pump based on a double Organic Rankine Cycle and an oil-free Compressor-Turbine Unit

•Experimental investigation of an organic Rankine cycle driven heat pump.•Integrated, fully hermetic and oil-free system with a heating capacity of about 40 kW.•Use of micro-turbomachines supported on gas bearings.•Presentation of the experimental results obtained with a first prototype.

This paper presents the experimental investigation of a concept of Thermally Driven Heat Pump (TDHP), based on the coupling of a vapor compression heat pump cycle and an Organic Rankine Cycle (ORC). The studied concept uses a single stage centrifugal compressor directly coupled to a single stage radial inflow turbine. The shaft is rotating on gas bearings, which allows the system to be oil-free. Like most of the other TDHP's, this system has the advantage to work with a variety of fuels or heat sources like wood pellets, natural gas, solar heat, geothermal heat or waste heat. A prototype using R134a as working fluid and with a heating capacity of about 40 kW has been developed. The results of the first tests are presented.