Research On Integrated Device Of Heat Pump Air Gap Membrane Distillation

Membrane distillation is a new separation technology,which can separate feed liquid at low temperature and atmospheric pressure and has the feature of high retaining rate.Membrane distillation has a good application prospect in the fields of water treatment,food,biology,chemical industry and pharmacy.Air gap membrane distillation has the advantages of high thermal efficiency,simple structure and easy to industrialize when it is used to treat heat sensitive liquids.Heat pump can produce multiple heat energy and cold energy by consuming a small amount of electric energy.By integrating heat pump with air gap membrane distillation,it has the comprehensive advantages of low investment and low energy consumption for the concentration of heat sensitive liquid.Based on this,theoretical and experimental research on the heat pump air gap membrane distillation integrated device was carried out systematically in this paper.Firstly,the structure of air gap membrane distillation module was designed and analyzed.A comparative analysis of external sleeve air gap membrane distillation module,cooling surface built-in air gap membrane distillation module,and external coiled air gap membrane distillation module was carried out.The results showed that the external coiled air gap membrane distillation module has the advantages of simple structure and controllable coolant flow distribution.The characteristic equations were listed and the performance simulation software was compiled for the external coiled air gap membrane distillation module with hollow fiber hydrophobic membrane.The change of the performance indexes such as permeate flux and thermal efficiency with the key parameters was calculated and simulated.Secondly,a heat pump membrane distillation integrated device is designed based on the external coiled air gap membrane distillation module.The characteristic equations were listed and the performance simulation software was compiled for the integrated device.The change of the performance indexes such as water production rate and gained output ratio with the key parameters was simulated.Guided by the above work,an experimental device of the heat pump air gap membrane distillation based on the external coiled air gap membrane distillation module was designed and produced.Apple juice with sugar degree of 11°Brix was used as the feed liquid.The feasibility of apple juice concentration at atmospheric pressure and low temperature(Below 50℃),the change rules of key parameters with time in the startup run phase,The actual data of the main performance indexes during stable operation were researched systematically.the results showed that under stable operating conditions,the heating coefficient of heat pump was 3.53,the permeate flux was 0.920kg/(m2·h),the thermal efficiency was 0.60,the gained output ratio of the integrated device was 1.64.At the same time,the experimental value of performance indexes was compared with the theoretical simulation value,and the corresponding improvement scheme was put forward.