| With the rapid development of social economy and increasing demand of the indoor thermal comfort,the energy consumption of building has increased year by year,which account for 32% of total energy consumption in China.Building energy conservation has a very important significance under the background of the increasing shortage of energy.This paper compares and optimizes the thermal performance of several common energy-saving walls in hot summer and cold winter regions,so as to use energy-saving wall more reasonably in engineering practice to reduce the energy consumption of building envelope structures.The thermal performance of hollow block and phase change material(PCM)block wall was tested by using the phase transition temperature box,and FLUENT software was used for calculation.The results show that the maximum relative error of the experiment and simulation is 2.57%,which illustrates the feasibility of the FLUENT software to simulate the heat transfer process of the block wall.Comparing the thermal performance of the hollow blocks,the hollow blocks filled with XPS,and the hollow blocks filled with PCM,the results show that the hollow blocks filled with XPS can increase the thermal resistance of the block by 32.27% and reduce the heat flow into the room by 23.87%.The hollow blocks filled with PCM can greatly improve unsteady thermal performance,and the attenuation multiple,the delay time and the temperature attenuation increase by 756.2%,40% and 10.17% respectively.At the same time,the heat flow amplitude reduces by 88.24%.The effect of XPS position in the hollow block on the thermal performance of the block wall is negligible,PCM filled in the hollow block near the outdoor side can significantly improve its thermal performance.Aiming at the problem of insufficient thermal performance of a hollow wall with a single filling material,a composite hollow block containing both PCM and XPS was proposed,and the thermal performance of composite hollow block was simulated and compared with that of the hollow block.The results show that compared to the single-layer PCM block wall,the heat flow into the room of the wall filled with a single-layer PCM and a single-layer XPS can reduce 26.17%,and that of wall filled with a single-layer PCM and double-layer XPS can reduce 42.20%.Compared with these two kinds of multilayer composite hollow blocks,the heat flow into the room of the double-layered XPS wall is reduced by 20.35%.In addition,the thermal performance of the block wall is best when the phase transition temperature of the PCM near the outdoor side is 0.8°C lower than the average outdoor air temperature and the phase change temperature of the PCM near the interior side is 3°C higher than the indoor temperature.In order to solve the problem that the single PCM cannot meet the requirement of energy saving all year round,the thermal performance of the double layer PCM concrete hollow block with different phase transition temperature is analyzed in this paper.It is found that the thermal performance of block wall decreases with the increase of PCM thermal conductivity in the air layer.In summer conditions,the thermal conductivity of the PCM in the air layer near the outdoor side has greater influence than that of PCM in the air layer near the indoor side.In winter conditions,the thermal conductivity of the PCM in the air layer near the indoor side plays a decisive role in the changes of the wall thermal performance.Therefore,the phase transition temperature of PCM,the thermal conductivity and the relative position of PCM in the block have great influence on the thermal performance of the block wall Filling PCM can greatly increase the attenuation factor and delay time of the wall.Filling XPS can greatly reduce the heat load generated by the envelope structure.The combination of the two steps can improve the overall thermal performance of the block wall,and the three types of block walls selected in this paper meet the current energy conservation code requirements. |
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