Study On The Regulation Of Heat Pump Multi-effect Membrane Distilation Equipment

Membrane distillation has the advantages of low temperature operation in normal pressure,which can be used to separate and concentrate or purify heat sensitive liquid material,high concentration liquid material and so on.It has been widely applied in separation and concentration of food industry,pharmaceuticals industry and chemical industry.Heat pump multi-effect.Heat pump unit and multi-effect Membrane modules were integrated into heat pump multi-effect membrane distillation system.In addition,system dynamic performance was proposed to obtain the appropriate regulation scheme which had significant influences on the energy consumption,operation reliability and service life of the equipment.In this paper,heat pump two-effect direct contact membrane distillation equipment was taken as the representative and the theoretical and experimental study on the regulation of the equipment was carried out systematically.In order to improve the issues such as short flow,a cross-flow hollow fiber membrane module for heat pump membrane distillation was proposed.The structure and equation of membrane module are presented and the change rules of heat efficiency and membrane flux with the key factors was calculated and analyzed.Regarding the above research as guidance,a cross-flow hollow fiber membrane module for membrane distillation was designed and its performance was also tested.The result showed that feed inlet temperature changed from 45 ? to 56 ? when rate of feed flow and condensate flow were both 1.8g/s.When condensate outlet temperature changed from 36 ? to 46?,the membrane flux was from 1.5kg/(m2·h)to 2.5 kg/(m2·h)and the thermal efficiency was up to 43%to 53%which was increased by more than 30%compared with the traditional shell and tube type hollow fiber membrane distillation module.The physical model and mathematical model of the heat pump two-effect membrane distillation system were built and the calculation software was worked out.The change rules of equipment status parameters and performance indexes were analyzed with auxiliary cooling device,without auxiliary cooling device and when liquid tank volume or initial operating condition parameters changed.The result showed that the first effect material temperature stably reached 70 ? and the second effect material temperature could stably reach 49 ? when the initial temperature of material and condensed water which were both 3kg was 30? and the auxiliary cooling device started and set the heat dissipation of 635W after 50min.This moment,the first effect and second effect thermal efficiency were both 47.5%,the first effect membrane flux was 1.6kg/(m2 · h)and the second effect membrane flux was 1.06 kg/(m2·h).The heating coefficient of heat pump was 6.3 and the gained output ratio of system was 6.25.The experimental heat pump two-effect membrane distillation equipment was developed.The dynamic characteristics of the equipment under variable conditions were studied experimentally.The result showed that the dynamic rules of the experimental equipment ware basically consistent with the theoretical analysis and the auxiliary cooling device could be used to nicely control the working condition of the equipment.