Experimental investigation of tracking paraboloid and box solar cookers under Egyptian environment

Abstract

Two full tracking solar cookers, namely a paraboloid dish solar cooker (PDSC) and a booster mirror solar box cooker (BMSBC) have been designed, constructed and tested during a winter season in Cairo (30° N and 30° E). The cookers are made simple, durable and of low cost. Tests are carried out to compare the performance of these two cookers under the same operating conditions. The results showed that the rate of cooking of the PDSC is higher than that of the BMSBC. Also, the PDSC can handle various types of cooking even under the intermittent sunny and cloudy conditions of the winter.The effect of wind speed on the heat loss from the receiver is of utmost importance for the evaluation of PDSC performance. Therefore, the effect of wind speed on the heat loss coefficients from new or black painted receivers is experimentally determined, analysed and presented in graphical form. The overall heat loss coefficients are correlated in terms of wind speed and surface conditions (painted or unpainted). During the indoor test, the wind speed was varied from 0 to 8 m/s. Based on these experimental results, a wind shield has been designed to reduce the wind effect. Tests confirmed that the wind shield improves the PDSC performance and allows boiling to take place even for high wind speeds. This is confirmed by the thermal analysis which shows reductions of 24 to 35% in the heat loss from the receiver with the presence of the wind shield.