Thermal performance evaluation of the funnel solar cooker of different funnel lengths implemented in Nagongera, Uganda.

Abstract

The aim of this study was to evaluate the thermal performance of a funnel solar cooker with different funnel lengths. Four funnel solar cookers of varying funnel lengths were constructed at Nagongera, in Tororo District, Uganda from cheap locally available materials. After construction, four blacked cooking pots of the same size filled with 1 kg of water were each placed in a cooker from 09:00 to 17:00 hrs. The temperature of the water in the pots was recorded after every 2 hours. The maximum temperatures of 93 °C, 84 °C, 68 °C and 58 °C for the funnel lengths of 50 cm, 42.6 cm, 32 cm and 23.3 cm, respectively were achieved at 13: 00 hrs for the average solar intensity of 684 W/m2 and ambient temperature of 27.9 °C. Similarly, as the funnel lengths increased from 23.3 cm to 50 cm, the thermal efficiency of the cooker increased from to 29.2% to 33.2% due to increased solar collecting surface. This indicates that the cooking temperature and thermal efficiency depended on the funnel lengths of the cooker and the time of the day. The results obtained were suitable and therefore the funnel solar cooker can be introduced to the community. Keywords: Funnel solar cooker; Thermal performance; Time of the day; Funnel length