双压膨胀有机朗肯循环中低温余热发电系统的热力性能

基于热力学第一定律与第二定律分析法，结合动量定理与质量守恒定律构建一种双压膨胀有机朗肯循环（ORC）中低温余热发电系统热力性能的预测模型，研究热源温度、蒸发温度、夹点温差、闪蒸压力、循环倍率、喷射压缩器引射流体在混合室进口的马赫数、工质泵、向心透平及螺杆膨胀机的等熵效率对系统的净输出功率、热效率、余热利用率及(火用)效率等热力性能的影响。结果表明，系统的净输出功率与(火用)效率随着热源温度、蒸发温度、循环倍率及透平等熵效率的增大而升高，但随着夹点温差、闪蒸压力的增大而降低；系统的热效率随着蒸发温度、闪蒸压力及透平等熵效率的增大而升高；系统的余热利用率随着热源温度、循环倍率的增大而升高，但随着蒸发温度、夹点温差、闪蒸压力的增大而降低。当循环倍率k=2时系统的净输出功率、(火用)效率及余热利用率分别比常规单级ORC系统绝对提高了230.9kW、10.1%和17.9%。

Thermodynamic performance of dual-pressure expansion organic Rankine cycle power generation system driven by low-middle temperature waste heat

Based on the first and second law of thermodynamics, the law of momentum and the law of conservation of mass, the predict model of the thermal performance of a dual-pressure expansion organic Rankine cycle system that recovery low-temperature waste heat was developed. The effect of the temperature of waste heat, evaporation temperature, pinch point temperature difference, flash pressure, circulating ratio, the Maher number in the inlet of the mixing chamber of the ejector, the isentropic efficiency of the pump, turbine and screw expander on the thermal performance of the ORC system was studied. The results indicated that increasing the temperature of waste heat, evaporation temperature, circulating ratio and isentropic efficiency of the turbine has been shown to increase the net output power and exergy efficiency, but they decrease as the pinch point temperature difference and the flash pressure increase. The thermal efficiency increases as the evaporation temperature, flash pressure and the isentropic efficiency of the turbine increase. Increasing the temperature of waste heat and the circulating ratio has been shown to increase the waste heat utilization ratio, but it decreases as the evaporation temperature, the pinch point temperature difference and the circulating ratio increase. On the conditions of k=2, the net power output, the exergy efficiency and the waste heat utilization efficiency are 230.9 kW, 10.1% and 17.9% higher than those of the conventional single-loop ORC system, respectively.