Loss coefficients from solar flat-plate collectors

In this paper an expression for the accurate computation of the overall heat loss coefficient, UL--including front, edge and rear losses--from a solar flat-plate collector has been derived. This expression is used and values of overall heat loss coefficients and overall collector efficiencies have been computed for various plate temperatures, tp, of 50 to 130°C in steps of 10°C, for ambient temperatures, ta, of zero to 50°C in steps of 10°C for the number of glass covers, N, of zero, 1 and 2 for tilts of the collector from the horizontal, B, of zero, 30° and 45°, for plates with emittances, Ep, of between 0·1 and 0·95, for plates with absorptivities of 0·7, 0·8, 0·9 or 0·95, for solar intensities, H, of 150 to 900 W/m2 and for wind speeds, w, of 1·5, 2·5, 4·0 and 5·5 m/s. Graphs are plotted to show the effects of the absorptivity and emissivity of the cover plate, the number of layers of cover glass, wind speed, tilt of the collector, ambient temperature and solar radiation on collector performance.