Thermal performance analysis of solar box cookers using different fin configurations: An experimental investigation

In this work, the performance of a low-cost solar box cooker (SBC) is experimentally investigated by fixing fins to the cooking utensils to improve the thermal performance and cooking rate. Four different configurations of water-based cooking boxes were evaluated: without fins, and with pin, cross, and hexagonal fins. To enable direct comparison, all fins opted for the experiments are of equal height (50 mm) with the same outer diameter (6 mm). The system was tested under outdoor conditions at different times of the day to determine the time taken by water to reach 100 °C. The optical efficiency of the designed SBC is 0.120 as per the stagnation test condition, for an absorber plate temperature of 135 °C. Maximum cooking powers of 96.54, 96.49, and 97.02 W and energy efficiencies of 60.20, 63.21, and 64.46% were obtained for pin, cross, and hexagonal fin-based SBCs. These efficiencies are higher than that of the reference SBC by 7.28, 12.65, and 14.88%, respectively. The modified SBC with hexagram pin fins extends the fin surface area for intercepting solar irradiance and exchanging heat with the working fluid. Hence, it augmented the cooking power, exergy output, energy efficiency, exergy efficiency, heat transfer coefficient and heat loss coefficient by maximums of 7.73, 16.41, 14.88, 8.47, 31.80, and 6.17%, respectively. Furthermore, an economic analysis is conducted to explore the cost savings and payback period of the hexagonal fin-based SBC unit in comparison with the conventional SBC unit. Such an evaluation showed that the SBC units with and without fins are expected to save about 1495 and 1172 MJ of fuel equivalent per year, respectively. Graphical abstract