Theoretical research on working fluid selection for a high-temperature regenerative transcritical dual-loop engine organic Rankine cycle

In this paper, a regenerative transcritical dual-loop organic Rankine cycle is proposed to recover the waste heat of the exhaust, engine coolant and all the residual heat of the HT loop. Double regenerators are adopted in this system. Transcritical cycles are used in both loops. Hexamethyldisiloxane (MM), octamethyl cyclotetrasiloxane (D4), octamethyltrisiloxane (MDM), cyclohexane, toluene and n-decane are chosen as the candidate working fluids of the HT loop and R143a is chosen as the working fluid of the LT loop. Influences of inlet temperature of turbine THT (T3) on mass flow rates (mf,HT and mf,LT), net output power (Wnet), energy conversion efficiency (ηec), volumetric expansion ratio (VER), ratio of power consumed to power output (COR) and component irreversibility are analyzed and performance comparison of these working fluids is also evaluated. Results show that toluene possesses the maximum Wnet (42.46 kW), highest ηe (51.92%) and ηec (12.77%). The increase of T3 worsens system performance, decreasing Wnet, ηe and ηec. Condenser CLT and turbine TLT possess the least system irreversibility. In addition, turbines and exhaust evaporators are optimized components.