Experimental study on the influence of pump frequencies and oil flow rates on the performance of organic rankine cycle systems

The organic Rankine cycle system can fully utilize the low-temperature waste heat generated by oil-free scroll air compressors, enhancing energy reuse efficiency. The heat source temperature (HST), working pump frequency, and filling quantity of the working fluids varied to achieve variable operating conditions for the experimental system. Experimental studies showed that the working pump frequency has a significant impact on the theoretical shaft power of the expander compared to the HST and the filling quantity (FQ) of the working fluids. At a working fluid filling quantity of 8 kg and HST of 120 °C, increasing the working pump frequency from 10 to 50 Hz results in the theoretical shaft power of the expander, power consumption of the working pump, and the system thermal efficiency varying in the ranges of 0.993–1.777 kW , 0.063–0.143 kW and 4.979–6.436 %, respectively. While elevating the frequency of the working pump leads to a corresponding rise in the theoretical shaft power of the expander, it also increases the power consumption of the working pump. Lubricating oil has a considerable impact on system performance. At an HST of 120 °C, the net system work attains a maximum value of 2.093 kW with 100 % lubricant and pump plunger stroke (PPS).