Research On Heat Transfer Performance And Energy Analysis Of Combined Phase Change In Building Envelope In Four Distinctive Season District

Building energy conservation is vital to the realization of energy saving and emission reduction.It is an important way to realize building energy saving by improving the thermal insulation performance of building envelope.Improving the heat capacity of wall by using phase change material,which can regulate air conditioning and heating load.However,with more and more research on the phase change envelope,it is found that it has the above advantages,there are still some problems in engineering practice,including the phase change plate is placed in different position in the project,producing unnecessary heat to the room at night,energy saving efficiency,increasing energy consumption,if the transformation could take into account the two seasons of winter and summer.In order to solve the above problems,in this paper,the optimum phase change material combination in the cold winter and heat summer region is derived by using the maximum effective energy of phase change thermal storage.The optimal phase transition temperature is verified by the principle of minimum heat dissipation,selecting composite phase change materials based on the best phase transition temperature like acetic acid,azelaic acid,sebacic acid and Na2CO3·10H2O.According to previous studies on heat transfer of phase change materials by enthalpy method,numerical simulations were carried out using the two methods of the two seasons of winter and summer of the composite phase change material.The temperature of the inner wall surface of the composite phase change material is higher than that of the outer wall in summer,the minimum temperature of the inner wall surface of the composite phase change material is higher about 3.29 centigrade and the average temperature is higher about 0.66 centigrade.The temperature of the inner wall surface of the composite phase change material is higher than that of the outer wall in winter,the minimum temperature of the inner wall surface of the composite phase change material is higher about 1.41 centigrade and the average temperature is higher about 0.16 centigrade.In order to verify the above inference,energy saving effect of composite phase change material,establishing the numerical models of three kinds of phase change envelopes and originalstructures.The dynamic heat transfer performance of three kinds of phase change envelopes under the conditions of hot summer and cold winter zone are analyzed.MATLAB and ecotect simulation results show,the maximum energy saving efficiency of composite phase change material is 22.5%in daytime,average energy efficiency is 17.1%.The cooling energy consumption in summer decreased 8.1%,12.2%,12.2% and 15.2%.In the night energy release phase of phase change material,in summer,the storage energy is more and the location is close to the outside of the envelope,so it is convenient to dissipate heat to the outside world.The temperature of the inner wall surface decreases significantly,reducing the unnecessary heat dissipation of the phase change material to the room.Compared with the original enclosure structure in summer,the cooling energy consumption decreases 8.1%,12.2%,12.2% and 15.2% in summer.The heating energy consumption of the combined phase change material is lower than the phase change material applied in winter and the phase change material applied in summer which is about 0.6%,10.2%,1.5%,14.5% decreased in summer and 10.1%,6.3%,5.5%,8.1% in winter.Compared with the original enclosure structure in winter,the winter heating energy consumption increased 11.8%,6%and 10.4%.The heating energy consumption of the combined phase change material is lower than the phase change material applied in winter and the phase change material applied in summer which is about 16.6%,9.3%,9.8% decreased and 9.1%,3.9%,8% increased.From the above analysis,it can be seen that in this paper,the composite phase change plate of the optimal phase change temperature can basically meet the requirements of winter heat preservation and heat insulation in summer.It has great potential for energy saving by using this form in hot summer and cold winter zone.