高效平板集热器件吸热面与透明盖板间距优化

OPTIMIZING THE SPACING BETWEEN ABSORBING PLATE AND GLAZING FOR A HIGH-EFFICIENCY FLAT-PLATE COLLECTOR UNIT

为减小高效平板集热器件边框对吸热板的遮光损失,建立了平板型集热器件平均有效吸热面积系数的计算模型。利用此模型对平均有效面积系数随板间距、倾角、纬度的变化进行了详细分析。结果表明,平均有效面积系数随板间距的增大而减小,冬季最明显;倾角小于15°或大于75°对集热器件平均有效面积系数均不利。为便于应用,给出了季均和年均有效面积系数不小于0.90的临界板间距。鉴于对流热损失较小的合理板间距为4～6cm,拟推荐北纬20°、30°、40°、50°使用的平板集热器件最大板间距分别约为5.5、5.0、4.5、4.0cm,相应年均有效面积系数均大于0.90。在设计过程中,可参照该文研究结果,尽量达到对流热损失最小化。

To reduce shading-loss by its sidewalls of a of mean effective heat-absorption area coefficient has cient with spacing between absorbing plate and high-efficiency flat-plate collector unit, the calculation model been built. The variations of the mean effective area coeffi- glazing , tilt angle, and latitude have been analyzed using this model. The results showed that the mean effective area coefficient decreases as the spacing increase; especially in winter. It is adverse to improve the mean effective area coefficient when the tilt angle is less 15° than or greater than 75°. Critical values of seasonal and yearly effective area coefficient greater than or equal to 0.90 have been given to be conveniently applied in practice. In view of the reasonable spacing of 4-6 cm for smaller convective heat-loss, the maximum plate spacing of 5.5, 5.0, 4.5 and 4.0 cm has been recommended for a collector unit used in north latitude of 20°, 30°, 40° and 50°. The corresponding yearly effective area coefficients are greater than 0.90. In the practical design of the high-efficiency flat-plate collector unit, the convective heat-loss and shade loss should be minimized on the basis of the results of this work.