Study of Second Figure of Merit of Box Type Solar Cookers by Semi-Log Plot Method Using Instantaneous and Averaged Values of Climatic Variables

Abstract

Test procedures have been proposed to evaluate thermal performance of solar cookers: box type [1] and concentrator type [2]. The performance of a box-type solar cooker can be represented in terms of two figures of merit, F1 and F2, which can be determined by simple thermal tests and to characterize the cookers [1]: studies have resulted in the Indian Standards [3,4] on solar cookers. F2 is obtained from the water-heating test using the experimental data on water temperature (Tw) and the climatic variables: insolation (I) and ambient temperature (Ta). It takes into account the climatic variables through a dimensional group consisting of [(Tw-Ta)/I]. It was shown that F2 could be obtained by using an equation involving natural logarithm of a function with this dimensional group. The Second figure of merit can also be determined by using a semi-log plot [5].