Thermal performance of solar air collector with slit-like perforations

To offer a potentially low-cost and high-efficiency option for once-through applications,the unglazed transpired solar collector was studied. The semi-empirical correlation of overall heat exchange effectivenessε for UTC with circular holes was proposed to verify whether it being fit for this kind of absorber with slit-like perforations. The results show that in certain parameters,the predicted values of ε are very close to measured values,and the root mean square difference in betweens about 0.10,so the modle is suitable. Based on experimental results,this kind of absorber is proved to be feasible,with highest value of ε,up to 0.81. In addition,with the increase of γ,overall heat exchange effectiveness ε will decrease,i.e.,the value of ε will decrease with the increase of suction velocity vs or the decrease of wind velocity uw. However,the actual value of solar radiation intensity G and ambient temperature T∞ have little influence on ε.

盖板式冲缝型空气集热器热性能的影响因素研究

提出一种盖板式冲缝型集热器,将吸热板设置成冲缝型,从而在不影响集热面积的同时增大了吸热板与空气间的对流传热系数;并采用数值模拟与实验验证相结合的方法对其热性能的影响因素进行研究。对比Matlab程序模拟值和实验值,两者基本吻合,空气出口温度的平均偏差为1.1℃,说明所建立的数学模型正确,可用来深入研究该集热器。研究结果表明,对于集热器结构尺寸和物理参数,冲缝当量直径对热效率和空气进出口温差的影响最大,其次是吸热板外表面发射率、盖板内表面发射率、盖板外表面发射率、平均冲缝间距和集热器高度;对于进口参数和环境条件,空气进口温度、环境温度和室外风速对热效率和空气进出口温差的影响均非常显著,而送风量和辐射强度对空气进出口温差影响显著。总体来看,若吸热板采用选择性涂层或盖板采用高透性低辐射玻璃,该集热器热效率较高,且与建筑一体化程度高,应在住宅建筑中大力推广。