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本文从传热学基本原理出发,针对封闭空气间层冬季保温状态及其对外墙保温系统热工性能的影响进行了探讨,通过理论计算和CFD模拟验证表明:1)外墙保温系统中空气间层的存在,增大了系统的热阻提高了系统的保温性能。当外墙保温系统中引入厚度d为20 mm的空气间层与保温板直接粘贴在外墙的系统相比,热阻增大0.75(m2·K)/W,热流密度降低了21%;2)在空气间层厚度d由0逐渐增大的过程中,传热方式由导热向对流转换。当d≤15 mm时导热占主导作用,当d>15 mm时对流占主导作用;3)空气间层厚度在0~20 mm范围内热阻随其厚度d的增加近似呈线性增加,增加趋势明显,随着d的继续增大,空气间层热阻的增量越来越小,当其间层厚度为65 mm时,热阻取得最大值,其间层厚度大于65 mm时,随着d的继续增大,热阻有减小的趋势;4)当空气间层厚度一定,随着高度H增大其热阻有增加的趋势,但其热阻增加的幅度随着高度H的增大而减小,H为14.57 m时,热阻取得最大值;5)在一定的封闭空气间层内,厚度的变化比高度的变化对保温系统热工性能的影响大。
In this paper, based on the basic principle of heat transfer, aiming at the effect of winter insulation in closed air space and its influence on the thermal performance of external wall thermal insulation system, the theoretical calculation and CFD simulation show that: 1) The presence of layers increases the thermal resistance of the system and improves the thermal insulation properties of the system. When the air space with the thickness d of 20 mm is introduced into the external wall thermal insulation system, the thermal resistance is increased by 0.75 (m2 · K) / W and the heat flux density is reduced by 21% compared with the system with the thermal insulation board directly attached to the external wall. 2) In the air layer thickness d gradually increased from 0 in the process of heat transfer from the heat transfer to convection. When d≤15 mm, the heat conduction dominates and the convection dominates when d> 15 mm. 3) The thermal resistance increases with the increase of the thickness d in the range of 0 ~ 20 mm with the thickness of the air layer increasing approximately linearly , As the d continues to increase, the increment of air layer thermal resistance is getting smaller and smaller, when the layer thickness is 65 mm, the maximum thermal resistance, the layer thickness is greater than 65 mm, with the continuation of d 4) When the thickness of the air layer is constant, the thermal resistance tends to increase as the height H increases, but the increase of the thermal resistance decreases with the increase of the height H Small, H is 14.57 m, the thermal resistance to obtain the maximum; 5) in a certain closed air layer, the thickness of the change than the height of the thermal insulation system thermal performance.