Question

Most solar-thermal collectors are ‘glazed’ meaning they are contained within a shallow box with a glass cover to insulate the absorber from heat loss by convection (e.g. from wind) while allowing the majority of the solar radiation to pass through to the absorber. Flat-plate solar collectors are typically tilted to optimise their solar energy absorption. The tilt angle affects the rate at which heat is lost from the collector due to natural convection. A collector is 0.96 m high and 2.4 m wide and has a gap between the absorber and glass of 24 mm. Assuming the absorber plate (the surface that heats the water) is maintained at 90 °C and the inside surface of the glass cover is maintained at 45 °C, calculate the rate of heat loss by natural convection between the absorber plate and glass cover for tilt angles of 0°, 45° and 90° from horizontal.

Answer 1