渔船主机余热驱动的氨水吸收式制冷装置制冷循环分析

Analysis on the refrigeration cycle of an aqueous-ammonia absorption cooling device driven by fishing vessel’s waste heat

为解决中国机动渔船普遍存在的燃料利用率低和渔获物保鲜能力不足问题,研究了一种通过回收渔船尾气中的余热来驱动制冷循环的氨水吸收式制冷装置。基于Aspen Plus软件建立了制冷循环模型,并分别对目标制冷量为15 kW、20 kW和25 kW的3个制冷循环过程进行了仿真计算。结果显示:在目标制冷量为20 kW和25 kW时,当制冷工质流量增至某一范围内时,尾气所能提供的热量无法使制冷工质析出足量的纯氨以满足制冷要求,发生器热负荷出现平直段,此时制冷系数曲线处于"低洼"阶段,对于整个制冷系统,其经济性、热效率均处于不利阶段,在实际运行中应当予以回避。在目标制冷量为15 kW和20 kW的两个循环中,制冷系数和实际制冷量在尾气流量较大时出现陡增趋势,不利于系统的可靠性和经济性,在实际运行中应进行适当控制。本研究为渔船尾气利用提供一种参考。

In order to solve the common problems of low fuel efficiency and insufficient fresh-keeping ability of motor fishing vessels in China,an aqueous-ammonia absorption refrigeration system driven by recovering waste heat from the exhaust gas of diesel engines was introduced.Based on Aspen Plus,the refrigeration cycle model was built,and the refrigeration cycle processes with a cooling capacity of 15 kW,20 kW and 25 kW were simulated.It was found that when the target cooling capacity is 20 kW and 25 kW,and the refrigerant flow increases to a certain range,the heat load of the generator appears straight,which illustrates that the heat provided by exhaust gas can’t make the refrigerant separate out enough pure ammonia to satisfy refrigeration requirements.At the same time,the“low-lying”period appears in the curve of the coefficient of performance,and for the whole refrigeration system,its economic and heat efficiency is at unfavorable level.Therefore such conditions should be avoided in actual operations.In the cycles with the target cooling capacity of 15 and 25 kW,the coefficient of performance and actual cooling capacity increases sharply when the gas flow is huge,which is harmful for the reliability and economy of the system,thus the gas flow should be properly controlled in actual operations.