Experimental study on a bifunctional heat utilization system of heat pump and power generation using low-grade heat source

Highlights: • A bifunctional system of power generation and heat pump is analyzed. • An experimental investigation of the bifunctional scroll machine. • System performance of ORC power generation mode and heat pump mode is presented. • Recommendations for the improvement of the bifunctional system. - Abstract: This paper presents an experimental study on a heat utilization system functioning as power generation and heat pump. The power generation and heat pump functions are achieved on the discipline of organic Rankin cycle (ORC) and reverse Carnot cycle (RCC), respectively. In the experiment, an inverter scroll compressor has been modified to implement dual functions of expansion with power output in power generation mode and compression with power consumption in heat pump mode. The thermodynamic cycles is fed with HCFC-142b and recovering heat from low-grade heat source at temperatures ranging from 50 to 95 °C. The results show good feasibility and stability of the bifunctional system under variable operating conditions. The performance of the bifunctional scroll machine is evaluated in terms of internal filling factor, isentropic efficiency and mechanical efficiency. In ORC power generation mode, the maximum power output is 2.95 kW and thermal efficiency reaches a maximum value of 3.95% at optimal work condition. In heat pump mode, the water temperature at the evaporator inlet is fixed at about 50 °C. The coefficient of performance (COP) ranges from 3.6 to 1.1 when the condensing temperature rises from 75 to 96 °C.