相变屋面隔热性能影响因素分析

Analysis of Factors Affecting Thermal Insulation Performance of Phase Change Roof

将相变材料制作成定型板材敷设在屋顶外层,白天通过相变吸收太阳辐射得热,屋顶内表面温度变化很小,减少了室外通过屋顶传入室内的热量。本文建立了该屋顶结构的简化动态热网模型(RC模型),对相变屋面热工性能的影响因素进行研究,包括相变材料的相变温度、相变温度半径和材料厚度等。结果显示,与非相变屋面相比,相变屋面内表面平均温度及最高温度都有了明显的降低;影响因素对内表面最高温度的影响较大;综合考虑相变屋面的衰减系数、延迟时间及经济性,夏热冬冷武汉地区夏季典型气象日下该屋顶结构适宜的相变温度范围为33～35℃,相变材料厚度为30 mm,该工况下相变屋面的衰减系数相比非相变屋面降低0.281,延迟时间增加6.65 h。

The phase change material(PCM)is made into a shaped plate and laid on the outer of the roof.During the daytime,the PCM absorb the solar radiation heat through the liquefaction,so that the inner surface temperature of the roof varies little and the amount of heat that is introduced into the room through the roof is reduced.A simplified dynamic thermal network model(RC model)of the roof is established in this paper,to study the effects of influencing factors on the thermal performance of the phase change roof,including the phase transition temperature,phase transition temperature radius and material thickness of the PCM layer.The results show that,compared with the roof without PCM,the average temperature and the maximum temperature of the interior surface of the phase change roof are obviously decreased;the influencing factors have great effects on the highest temperature of inner surface.The decrement factor and time lag of the phase-change roof under different conditions are compared and analyzed.Considering economic factors,the suitable phase transition temperature range is 33~35℃,and thickness of the PCM layer is 30 mm under the typical weather day outdoor temperature in summer in Wuhan.Under the optimum condition,the decrement factor of the phase-change roof is reduced by 0.281 compared with the roof without PCM,while the time lag is increased by 6.65 h.