Effect of thermal conductivity of absorber plate on the performance of a solar water heater

Abstract

The effect of thermal conductivity of the absorber plate of a solar collector on the performance of a thermosyphon solar water heater is studied by the use of the transient simulation system (TRNSYS) computer program. The system is assumed to supply hot water at 55° and 80°C representing both domestic and industrial uses respectively. Hot water of volumes 50, 125, and 250 l is consumed daily according to the Rand distribution profile. The results have shows that the annual solar fraction of the system and the collector`s characteristic factors (namely, fin efficiency factor, collector efficiency factor, and heat removal factor) have a very strong dependence on the thermal conductivity for its low values, and weak dependence is observed beyond a thermal conductivity value of 50 W/m °C for the solar fraction and beyond a value of 100 W/m °C for the characteristic factors. It is also observed that the annual solar fraction is improved by about 4%–7% and the characteristic factors are improved by about 12%–19% when a steel absorber plate is replaced by an aluminium one, whereas, the solar fraction and the characteristic factors are increased only about 1% and 3%, respectively, when a copper plate is used instead of an aluminium one.