1. The absorber plate and the adjoining cover plate of a flat-plate solar collector are at 70 and 35°C, respec- tively, and are separated by an air space of 0.05 m. What is the rate of free convection heat transfer per unit to convection heat transfer to or from the water, estimate the rate of heat transfer per unit width normal to the flow direction (W/m) from the absorber plate to the water.
2. As is evident from the property data of Tables A.3 and A.4, the thermal conductivity of glass at room tempera- ture is more than 50 times larger than that of air. It is surface area between the two plates if they are inclined at an angle of 60° from the horizontal?