中空纤维膜溶液热交换器的传热传质模拟研究

Simulation of Heat and Mass Transfer in Solution Heat Exchanger with Hollow Fiber Membrane

提出了一种适用于溴化锂吸收式制冷系统的新型溶液热交换器——中空纤维膜溶液热交换器.该溶液热交换器不同于传统的间壁式溶液热交换器,在高温浓溶液和低温稀溶液进行热量传递的同时,存在水蒸气的质量传递,质量传递的方向取决于膜两侧的水蒸气压差.应用分布参数法对溶液热交换器建立了溶液流动的传热、传质数学模型,并对顺流和逆流布置的流动过程进行了比较.研究结果表明:当溶液热交换器逆流布置时,沿程温差均匀,热量传递稳定,水蒸气由高温侧向低温侧的持续传质作用不但进一步浓缩了浓溶液,而且稀释了稀溶液,因此减小了发生器的热负荷和吸收器的冷负荷.

A solution heat exchanger with hollow fiber membrane applied in lithium bromide absorption systems was proposed. Unlike in conventional dividing wall type heat exchangers, water vapor mass transfer occurs with heat transfer and the direction of mass transfer depends on the water vapor pressure difference between the two sides of membrane. A mathematical model of heat transfer and mass transfer process in the membrane heat exchanger was established with the distributed parameter method, and its performances with the parallel-flow mode and the counter- flow mode were compared. The simulation result shows that with the counter-flow mode, the temperature difference is uniform along the flow path, and heat transfer and mass transfer are more steady. The rich solution can be concentrated and the weak solution can be diluted further, leading to lower heat loads of the generator and the absorber.