An experimental study on top heat loss coefficient of a box-type solar cooker

摘要

Top heat loss coefficient (U_t) is required for thermal performance evaluation of a box-type solar cooker. In the present work, the values of Ut were obtained from outdoor experiments undertaken to determine the First Figue of Merit (F_1) Ut was foundto vary from summer to winter. A comparison of values Ut obtained from the experiments with the values obtained from analytical equation showed the same trend. The effect of use of measured value of outer glass cover temperatre (T_2)., or estimated value of T_2, on Ut computed by analytical equation was also studied. The measurement of T_2 was found to be not essential for obtaining Ut by this equation. As obtaining T_2 by experiments also involves uncertainties, one might prefer to use existing correlations for T_2.