Thermal performance simulation of a parallel combined heating and power cycle

Abstract:

To solve the problems of low thermal efficiency and hard utilization of condensing heat in traditional low and medium temperature heat recovery systems, a parallel type organic Rankine cycle (ORC) and ejector heat pump (EHP) combined cycle (referred to as PCHP) was proposed. The heat engine cycle and heat pump cycle were organized in parallel and an external heat exchanger (EHE) was added. All the condensing heat could be recovered for the production of radiant heating water, and the thermoelectric ratio could be adjusted within a certain range. The energy analysis model and exergy analysis model of the system were established. The thermal performance of the combined cycle and ORC were compared and analyzed. The characteristics of component exergy destruction and system exergy flow were investigated, and the effects of working fluid flow ratio and evaporating temperature on the thermal performance of the system were analyzed. Results show that the heat recovery capacity and exergy efficiency of the combined cycle were increased by 60.83% and 30.76% compared with those of ORC. The two components with the highest exergy destruction were the generator and the EHE. The main reason for the low exergy efficiency of the EHE was the high temperature difference of internal heat transfer. The working fluid flow ratio had a significant effect on the thermal performance of the system. When the evaporating temperature was lower than 25.2 ℃, the adjustable range of the working fluid flow ratio was the largest. The research results can provide guidance for the research and development of high-performance low and medium temperature heat recovery systems.