Solar radiation is incident on a flat-plate collector at a rate of 260 Btu/h·ft2. The product of the transmissivty of glazing and the absorptivity of absorber plate is τα = 0.85 for this single glazing collector. The heat loss coefficient of the collector is 0.5 Btu/h·ft2·oF. The collector is at an average temperature of 120oF and the ambient air temperature is 67oF.
(a) Determine the efficiency of this collector.
(b) Determine the efficiency of a double-glazing collector whose τα value is 0.80 and the heat loss coefficient is 0.3 Btu/h·ft2·oF. Use the same collector and ambient air temperatures.