Theoretical Analysis of a Combined Thermoelectric Generator (TEG) and Dual-loop Organic Rankine Cycle (DORC) System Using for Engines' Exhaust Waste Heat Recovery

This paper presents a model system TEG-DORC that employs thermoelectric generator (TEG) as a topping cycle integrated with a dual-loop organic Rankine bottoming cycle (DORC) to recover exhaust heat of internal combustion engine (ICE). The thermodynamic performance of TEG-DORC system is analyzed based on the first and second law of thermodynamics when system net output power W_net, thermal efficiency η_th, exergy efficiency η_e and volumetric expansion ratio are chosen as objective functions. The model has many parameters that affect combined system performance such as TEG scale, evaporation pressure of high temperature ORC loop (HT loop) P_evp,HT, condensation temperature of HT loop T_cond,HT. It is suggested that HT loop has a vital influence on system performance. The results show that TEG-DORC system can significantly improve system performance, and system net output power gets maximum (30.69kW) when T_cond,HT is 370K and P_evp,HT is 4MPa, accordingly, the absolute effective thermal efficiency increases by 5.2%. The maximum thermal efficiency and exergy efficiency are 26.39% and 53.08% respectively. And applying TEG modules can't promote DORC system performance as expected.