Experimental investigation of a splitting organic Rankine cycle for dual waste heat recovery

The organic Rankine cycle (ORC) is an effective method for internal combustion engines’ waste heat recovery. The waste heat from internal combustion engines primarily includes exhaust gas and engine cooling water. However, single-loop preheating and dual-loop ORC configurations are difficult to balance the recovery efficiency of the dual heat sources and the complexity of the equipment. The splitting ORC, as an effective method for enhancing the utilization of waste heat sources, has been proposed.

This study developed for the first time a test bench for a splitting ORC with a recuperator (SR-ORC) for internal combustion engines’ waste heat recovery, aiming to verify the enhancement effect of the system’s performance by splitting the working fluid into two branches to recover the engine cooling water and exhaust gas waste heat respectively.

The research results indicate that there exists an optimal working fluid pump speed and splitting ratio to maximize the net output power and efficiency of the system. Moreover, under the engine condition of rotating speed of 1100 rpm and torque of 600 N·m, the system achieves a maximum net power output of 2.81 kW, a maximum internal combustion engine efficiency improvement of 1.6 %, and a maximum thermal efficiency of 10.1 % at the maximum heat source safety operating range. Compared to the non-splitting mode of this test bench with the same engine and heat source condition, these values represent a relative improvement of 8.3 %, 9.6 %, and 27.9 %, respectively.