Study On Solar Assisted Heat Pump Membrane Distillation Unit

Membrane distillation is the separation of volatile components from other components by using hydrophobic microporous membranes which allow vapor to pass through while liquid material cannot pass through the membrane wall.When the membrane distillation module works,heat source is needed at the material-liquid side to vaporize water in the feed,and cooling steam is needed at the condensate side,which consumes a great deal of energy in the whole process.The heat pump membrane distillation unit can produce multiple heat and cold energy by using heat pump to consume a small amount of energy,and the heat pump can provide heat and cold energy for the membrane distillation module.The photovoltaic solar heat pump membrane distillation unit uses photovoltaic panels to convert solar energy into electric energy,and then drives the heat pump compressor by photovoltaic energy.To realize the operation of the whole unit,it has broad application prospects in desalination water preparation,waste liquid treatment and concentration of agricultural by-products in power-deficient areas.In this paper,a systematic theoretical and experimental study has been carried out.In order to realize the reasonable technical coupling of solar photovoltaic power generation,heat pump and membrane distillation units,the three units are analyzed and studied respectively.The matching schemes among the three units are given,and the physical model of solar heat pump membrane distillation unit is constructed.Based on the background of making desalinated water from seawater,the mathematical model of membrane distillation unit of solar energy heat pump was established,the basic equations of each unit were given,and the performance simulation software of membrane distillation unit of solar energy heat pump was compiled.The effects of solar illumination intensity,seawater and desalination water flow,membrane hole diameter and membrane area on the performance of the unit were analyzed.The typical parameters of solar heat pump membrane distillation unit are determined as follows:the flow rate of seawater and desalination water should be 70 g/s-100 g/s;the diameter of hollow fiber membrane should be 0.25 m-0.4 m;the length of hollow fiber should be 400 mm-550 mm,and the number of hollow fiber should be 400-550;the temperature of membrane inlet module of desalination water should be appropriate.Higher value.The experimental device of solar heat pump membrane distillation was developed,and the output power of photovoltaic panels at different stages and the input power and device performance of heat pump compressor at different rotational speeds were tested.The results show that the optimum rotational speed of the compressor is 3500 rotational/min?4000 rotational/min.In this range,the heating coefficient of the heat pump can reach more than 4,and the membrane module can be used.The membrane flux is 1.3 kg/(m2.h),the thermal efficiency is 27.5%,the water production ratio is 0.35,the water production rate is 0.0678 kg/h,and the light water production ratio is 0.13 g/kJ.