Efficiency analysis of trilateral-cycle power systems for waste heat recovery-to-power generation

Numerous innovative heat recovery-to-power technologies have been resourcefully and technologically exploited to bridge the growing gap between energy needs and its sustainable and affordable supply. Among them, the proposed trilateral-cycle (TLC) power system exhibits high thermodynamic efficiency during heat recovery-to-power from low-to-medium temperature heat sources. The TLCs are proposed and analysed using n-pentane as working fluid for waste heat recovery-to-power generation from low-grade heat source to evaluate the thermodynamic efficiency of the cycles. Four different single stage TLC configurations with distinct working principles are modelled thermodynamically using engineering equation solver. Based on the thermodynamic framework, thermodynamic performance simulation and efficiency analysis of the cycles as well as the exergy efficiencies of the heating and condensing processes are carried out and compared in their efficiency. The results show that the simple TLC, recuperated TLC, reheat TLC and regenerative TLC operating at subcritical conditions with cycle high temperature of 473 K can attain thermal efficiencies of 21.97%, 23.91%, 22.07% and 22.9%, respectively. The recuperated TLC attains the highest thermodynamic efficiency at the cycle high temperature because of its lowest exergy destruction rates in the heat exchanger and condenser. The efficiency analysis carried out would assist in guiding thermodynamic process development and thermal integration of the proposed cycles.