glass cover; collectors with single glazing; collector; method; computation
An improved equation form for computing the glass cover temperature of flat-plate solar collectors with single glazing is developed. A semi-analytical correlation for the factor(f)the ratio of inner to outer heat-transfer coefficients—as a function of collector parameters and atmospheric variables is obtained by
regression analysis. This relation readily provides the glass cover temperature (T ). The results are compared (g) with those obtained by numerical solution of heat balance equations. Computational errors in (T) and hence in (g) the top heat loss coefficient (U ) are reduced by a factor of five or more. With such low errors in computation t of (T) and (U) , a numerical solution of heat balance equations is not required. The method is applicable over an (gt) extensive range of variables: the error in the computation of (U)is within 2% with the range of air gap spacing (t8) mm to 90 mm and the range of ambient temperature 08C to 458C. In this extended range of variables the errors due to simplified method based on empirical relations for (U) are substantially higher.