DefinePK

Abstract

A solar cooker requires absorber temperatures that are definitely higher than 100°C. A proper estimate of the heat losses is important to evaluate the solar collector efficiency. The heat losses from the bottom and the lateral sides of the collector are easily estimated from the knowledge of the thermal insulating materials. As for the heat losses from the top, they represent a more important fraction of the energy balance. Hence, a proper estimate of the top loss coefficient UL is relevant. In the present paper, some experimental data are used to evaluate UL. This evaluation is performed by using the electrical analogy, but also by means of some empirical correlations. The values of UL are plotted against time. The evaluations of UL with the absorber temperature are also plotted. Some statistical parameters such as MBE and RMSE are calculated. The study shows that UL is overestimated by the empirical correlations. In addition, for the triple glazing solar cooker studied here, the comparative study showed a better agreement between the top loss coefficient obtained from the electrical analogy and the prediction by the Malhotra et al., correlation.