Study On The Performance Of Phase Change Cold Storage Roof System Coupled With Earth To Air Heat Exchanger

With the continuous development of social economy,building energy consumption is growing rapidly.Tunnel wind is a kind of utilization form of renewable soil energy,which has been widely concerned because of its simple structure and low cost.The temperature in the deep soil is relatively stable all the year round,which can precool the outdoor air in summer,preheat it in winter,send it into the building,reduce or increase the indoor temperature.In theory,the soil energy is inexhaustible energy,but in the course of operation,the ability of tunnel to deal with air will decline.Phase change energy storage technology can solve the mismatch of time and space in the process of energy utilization,which is widely used in the field of building energy saving.By coupling the tunnel air with phase change energy storage technology,the cooling capacity can be stored during the tunnel air operation,and the tunnel air can operate intermittently to improve the operation efficiency of the tunnel air.The purpose of this paper is to study a kind of phase change cold storage system to store the air cooling capacity of tunnel.Firstly,the theoretical calculation of tunnel air and phase change roof is carried out,and the system form of tunnel air and the structure form of phase change cold storage roof are designed.Secondly,by melt blending and heating the n-decanoic acid(CA)and dodecanol(DE),the phase change cold storage material ca-de was prepared.Its performance parameters were measured by differential scanning calorimetry.The prepared phase change material is encapsulated in a customized iron box and a cylindrical rib on the surface of the iron box to form a phase change cold storage roof.In order to test the performance of the coupling system,three kinds of cooling tests were carried out in the experimental room:natural convection cooling,tunnel air 12 h timing cooling and tunnel air 8 h timing cooling.The duration of each test condition was 72 h.Through the experimental study,the indoor temperature,phase change material temperature and tunnel air outlet temperature under three working conditions are analyzed.In the experiment,the peak temperature and average temperature of the experimental room decreased,the thermal inertia of the room roof increased,and the peak temperature time of the indoor air delayed.Under the three working conditions,the indoor temperature of the coupling system of tunnel air and phase change cold storage roof is slightly higher.Because of the high ventilation efficiency of opening doors and windows,the temperature is the lowest under the natural convection ventilation.However,due to the instability of cold wind at night,the energy storage effect of phase change materials is not as good as that of tunnel wind under the condition of natural convection ventilation.The maximum temperature drop of the air is 8.63 ℃and 7.9 ℃ respectively under the 8 h and 12 h regular operation conditions of the tunnel air.Reducing the operation time of the tunnel air is conducive to the recovery of the temperature of the soil itself,so as to improve the cooling efficiency of the tunnel air cooling system.Based on the experiment,through the combination of tunnel air technology and phase-change energy storage technology,using clean energy soil energy for indoor cooling,the research shows that the coupling system can effectively improve the thermal comfort of indoor environment,and provide design reference for tunnel air storage cooling system.