Numerical Simulation Of Heat Transfer Characteristics Of Phase Change Energy Storage Wall With Heat And Cold Source

With the acceleration of national economic development and urbanization,energy consumption is increasing.Building energy efficiency in line with the national requirements to achieve carbon neutrality.There are many ways to realize building energy saving,one of which is to enhance the thermal performance of building envelope.The addition of phase change materials to the building envelope can improve the heat storage of the envelope and enhance its thermal insulation performance.Therefore,a double-layer phase change wall system with natural heat and cold sources is developed in this project.Numerical simulation method is used to analyze the change law of heat transfer characteristics of phase change wall under different seasons,different water temperature and flow velocity.Specific research contents are as follows:(1)Through literature review,several common phase change materials in building envelope were selected to compare and analyze the advantages and disadvantages of different types of phase change materials.Combined with the climate characteristics of hot summer and cold winter areas,52#paraffin and liquid paraffin were selected to make phase change materials at 30℃ and 18℃ respectively according to the ratio of 1:1 and 1:3.Then the expanded graphite-paraffin composite phase change material was prepared by porous matrix adsorption.(2)In view of the problems of incomplete phase change in winter and insufficient heat storage capacity in summer,the structure of traditional phase change energy storage wall was optimized in this topic,and a double-layer phase change energy storage wall of natural cold and heat source coupled with water system was developed.The wall is made of hollow brick with two holes on the interior side filled with low-temperature PCM and two holes on the exterior side filled with high-temperature PCM.(3)Fluent software was used to simulate heat transfer of phase change storage wall at water temperature of 303K,304K,305K,306K,307K,318K,319K,320K,321K,322K and water velocity of 1.1m/s,1.2m/s,1.3m/s,1.4m/s and 1.5m/s respectively The optimal water temperature and flow velocity in winter and summer were found by analyzing the liquid phase rate and the surface temperature of the inner wall.The study found that in summer,the optimal water temperature is 303k,the most appropriate flow speed is 1.3m/s;In winter,the optimal water temperature is 322K,and the most suitable flow speed is 1.2m/s.(4)Taking a villa in a residential area as an example,the energy consumption calculation was carried out by using BESI2020,and the total annual energy consumption generated by the application of ordinary wall and double-layer phase-change energy storage wall was compared.The result analysis report shows that compared with the ordinary wall,the double-layer phase change energy storage wall studied in this subject saves 23%energy in the aspect of heat consumption and 38%energy consumption in the aspect of cold consumption of the building envelope,achieving a certain energy-saving effect.