(火积)方法在低品位工业余热利用的换热网络优化中的应用研究

Application of entransy method in heat exchanger network optimization for low-grade waste heat utilization

低品位工业余热的有效利用对提高能源利用效率、减少CO2排放具有重要意义,能量系统集成和相应的换热网络优化是余热利用的有效方法.(火积)方法可以量化换热过程中的不可逆性,能够指导和评价换热网络的优化,但是(火积)方法在余热利用的换热网络优化中的实际应用案例较为缺乏.本文基于(火积)方法对某工业园区蒸汽凝水余热利用的既有换热网络进行了分析,通过减小换热过程(火积)耗散的原理进行了换热网络优化,使得高品位余热用于驱动吸收式制冷机满足当地的空调制冷需求,将高品位余热排放转换为低品位余热排放.优化的换热网络指导了实际蒸汽凝水余热利用工程改造.实验测试结果表明,采用的海水直接冷却的吸收式制冷机的制冷量达到3430 kW,COP达到0.76.蒸汽凝水换热过程的(火积)耗散降低了57.3%,蒸汽凝水余热利用的热效率和?效率分别提升了55.8%和81.1%,验证了(火积)方法在低品位余热利用换热网络优化中应用的有效性.

Efficient utilization of low-grade industrial waste heat is of great significance to improve the efficiency of energy utilization and to reduce CO;emission.Energy system integration and corresponding heat exchanger network optimization are effective solutions.The entransy method is suitable for quantifying the irreversibility of the heat exchange process and guiding and evaluating heat exchanger network optimization.However,there are relatively few cases in which the entransy method is applied to the heat exchanger network optimization for waste heat utilization.In this study,the waste heat utilization of steam condensate in an industrial park through a heat exchanger network was analyzed based on the entransy method.By reducing the entransy dissipation of the heat exchange process of the condensate,the existing heat exchanger network was optimized,and the high-grade waste heat was utilized by an absorption chiller for local air conditioning demands.As a result,the discharge of high-grade waste heat was converted to the discharge of lowgrade waste heat.The optimized heat exchanger network guided the redesign of the actual heat exchanger network.The testing results showed that the cooling effect of the developed seawater cooled absorption chiller reached 3430 kW,with a coefficient of performance of 0.76.The entransy dissipation of the heat exchange process of the condensate was reduced by 57.3%.The thermal efficiency and exergy efficiency of the heat exchanger network were increased by 55.8%and 81.1%,respectively.These results demonstrate that the entransy method is valid in the application of low-grade waste heat utilization through heat exchanger network optimization.