CAJ | 학술논문

采用螺杆膨胀机双循环系统回收低温余热用于发电,拟合有机工质R245fa的热物性参数进行热力设计计算,并提出2种确定蒸发温度的方法,对单位质量的热源,分别以系统净功率、系统效率为优化目标,结合热力学第一定律与第二定律评价2种方法的优劣性.结果表明：随着蒸发温度的升高,存在最佳蒸发温度使得系统净功率最大,而系统热效率逐渐提高;系统净功率最大时,系统对余热能量回收较大,且回收量最大,故选择以系统净功率为目标作为蒸发温度的优化方法;基于蒸发压力恒定不变,证明了余热回收热量、系统净功率和系统效率随着过热度的增加而减少,应尽量采用饱和状态蒸气动力循环.
채용라간팽창궤쌍순배계통회수저온여열용우발전,의합유궤공질R245fa적열물성삼수진행열력설계계산,병제출2충학정증발온도적방법,대단위질량적열원,분별이계통정공솔、계통효솔위우화목표,결합열역학제일정률여제이정률평개2충방법적우렬성.결과표명：수착증발온도적승고,존재최가증발온도사득계통정공솔최대,이계통열효솔축점제고;계통정공솔최대시,계통대여열능량회수교대,차회수량최대,고선택이계통정공솔위목표작위증발온도적우화방법;기우증발압력항정불변,증명료여열회수열량、계통정공솔화계통효솔수착과열도적증가이감소,응진량채용포화상태증기동력순배.
The screw expander dual--cycle system was adopted for power generation by recovering low-- temperature waste heat, for which thermal design calculation was performed by fitting the thermal physical parameters of organic working medium R245fa. Two approaches for determining evaporating temperatures were proposed and compared using first and second law of thermodynamics by taking the system net power and efficiency as the optimization objects for the heat source per unit mass. Results show that with the rise of evaporating temperature, there exists an optimal evaporating temperature, in which case the system net power achieves the highest, and the system efficiency grows gradually more waste heat and most exergy are recovered by the system when the net power of system reaches the highest, and the corresponding evaporating temperature is therefore determined as the optimal one; at a constant evaporating pressure, all the waste heat recovery, the system net power and the net efficiency reduce with rising superheat degree, so the saturated steam power cycle is recommended.