地面对流换热过程分析

Experimental investigation of convective heat transfer on the ground

全尺度实验测试了门窗夜间通风房间的围护结构内表面和地面热质的温度变化,分析了换气次数和地面与进风气流间初始温差对地面对流换热的影响.结果表明:换气次数为4.99~13.6次·h^(-1),地面与进风气流间初始温差为6.86~12.5℃时,地面平均对流换热系数不超过7 W·m^(-2)·K^(-1),局部对流换热系数不超过12 W·m^(-2)·K^(-1);换气次数较少时,由于少量室外冷空气在热压作用下由窗户下沿进入室内,使窗户附近地面的对流换热较强;地面对流换热量随时间逐渐减小,但平均对流换热系数变化不大.总之,换气次数越多,地面对流换热越强,但地面与进风气流间初始温差对地面对流换热过程的影响并不明了.

Temperatures of the inner surfaces of building envelope and the thermal mass of floor in a full-scale test room night ventilated through a window and a door are measured.The effects of air change rate and the initial temperature difference between the ground and the inlet air on the convective heat transfer on the ground are then analyzed.The results indicate that the average convective heat transfer coefficient(hc)on the ground during ventilation is not more than 7 W·m-2·K_1,and the local/ic is less than 12W·m-2K-1if the air change rate is between 4.99h-1and 13.6-1and the initial temperature difference between the ground and inlet air is between 6.86℃and 12.5℃.In the case of small air change rate,the convective heat transfer on the ground near the window is enhanced by the external cold air entering through the low part of window because of the thermal pressure.During the ventilation,the average heat flux on the ground decreases gradually with time,and the average CHTC does not vary significantly.The greater the air change rate,the more effective the convective heat transfer on the ground.However,the influence of the initial temperature difference between the ground and the inlet air on the convective heat transfer on the ground is unclear.