Energy Consumption Analysis Of Membrane Distillation System Integrated With Thermoelectric Heat Pump

Membrane distillation is a new membrane separation technology that uses the steam pressure difference on both sides of hydrophobic microporous membrane to drive steam penetration.Its main advantages are:high rejection rate and mild operating conditions.However,the system energy consumption is high as a result of simultaneous heating the feed and cooling the permeate.In order to improve the energy efficiency of membrane distillation and reduce the complexity and cost of system configuration,direct contact membrane distillation system integrated with thermoelectric heat pump is proposed.Based on the construction of the DCMD/TEHP model,the energy efficiency performance of different integrated processes was comprehensively evaluated through numerical simulation.The main work of this paper includes the selection of thermoelectric heat pump（TEHP）suitable for direct contact membrane distillation（DCMD）unit and the energy efficiency analysis of integrated thermoelectric heat pump direct contact membrane distillation system（DCMD/TEHP）.（1）Firstly,based on the heat and mass transfer of membrane distillation,a one-dimensional physical model was established.The membrane distillation process of flat membrane module was simulated by numerical calculation.The simulation was verified by the results of membrane distillation verification experiment under corresponding working conditions,and it was found that the relative average deviation is less than 10%.The simulation program was used to calculate the membrane distillation process under different operating conditions.The results showed that increasing the feed side temperature,increasing the feed flowrate,reducing the permeate side temperature,increasing the permeate flowrate,and reducing the feed salinity all had a positive effect on the permeate flux.Secondly,the performance of the thermoelectric refrigeration system was tested,and the method that can accurately predict the performance of TEHP under different working conditions was obtained by fitting and optimizing the experimental data.Finally,for the set DCMD process,the critical refrigeration coefficient(^*)of TEHP was obtained by optimizing the energy efficiency of the traditional DCMD system.To achieve energy-saving effect,the COP_C of the selected TEHP under the specified working conditions was greater than^*.（2）On the basis of accurately describing the structural characteristics of coupled thermoelectric hot film modules in different integration process schemes,the process technology of DCMD/TEHP system was clarified.Through the energy efficiency measurement experiment of DCMD/TEHP system,the result showed that the integration mode and input power of TEHP were the significant factors affecting the energy efficiency of the system.Corresponding to various TEHP integration schemes,based on the MD integrated with TEHP,feed mixing unit,permeate overflow unit,feed separation unit,the mathematical and physical model of DCMD/TEHP system was established,and the corresponding calculation program was developed on the MATLAB platform to simulate the seawater desalination process.Through the DCMD/TEHP process simulation verified by experiments,the process strengthening effect of different integrated processes was explored,and the operation guideline for improving the system energy efficiency under the corresponding integrated processes was given,The research showed that within the range of investigated parameters,the energy-saving degree of DCMD/p TEHP integrated process with countercurrent operation can reach 12%,which can effectively reduce the process energy consumption of DCMD system.In addition,by appropriately increasing the permeate flow rate,reducing the feed liquid flow rate,and improving the feed liquid reflux ratio,it was conducive to improving the comprehensive energy efficiency of the system,the maximum increase can reach 53%.The research results of this paper provide theoretical guidance for the matching and optimization of thermoelectric heat pump and membrane distillation unit,and lay a foundation for the application research of DCMD/TEHP system.