Search

The size and shape of solar box cooker is determined by the volume of the vessel, which in turn depends on the number of family members. The primary objective of this study is to overcome the obstacles inhibiting researchers from crafting solar box cookers tailored to their specific research needs, as well as hindrances preventing manufacturers from effectively bringing them to market. This experimental study aims to identify two novel optimal volumetric efficiencies (VE1 and VE2) to minimize cooking time. To achieve this goal, we employed two identical solar box cookers made from the same materials and four vessels. The results obtained clearly show that the absorber temperature reached a maximum value of 124.9 °C and the boiling time was the shortest 02h50 when the first volumetric efficiency VE1 had the least value of 6.2% and the second volumetric efficiency VE2 had the greatest value of 100%. It is concluded that these two volumetric efficiencies could serve as benchmark parameters for future research, providing a standardized reference for developing solar box cookers of varied shapes and sizes under the same climatic conditions.

The primary goal of this paper is to assess the thermal behaviour of Earth-to-Air Heat Exchanger (EAHE) under continuous operation mode during the cooling period in warm climatic conditions. An experimental setup was conducted in Biskra University (Algeria) to test the ability to use EAHE as an alternative solution to conventional air conditioning systems. Besides, a transient numerical approach for the flowing air within the EAHE was developed using energy balance equations, discretised by the implicit finite differences method and solved by Thomas method. Furthermore, the transient temperature profile of the soil around the EAHE was investigated in order to determine the adiabatic radius of the soil as a function of the duration of operation. In this context, a transient semi-analytical model was integrated to the air model to estimate the transient EAHE’s performance deterioration. This deterioration is produced by the thermal saturation of the soil, which is influenced by the heat released from the air inside the pipe. Results showed that continuous operation for a duration of four days has minimal impact on the outlet air temperatures due to the implementation of night purging. Furthermore, the design and thermal efficiency of the EAHE are impacted by factors such as higher air velocity and reduced soil thermal conductivity.

In this research study, the development of a theoretical model to estimate the efficiency of a double pass solar air heater (DPSAH) was the main objective. The mathematical model was compared to experimental results and found to be in agreement, both qualitatively and quantitatively. The model used energy balance equations to determine the outlet temperature and could solve the temperature equations of each component of the heater simultaneously. A matrix inversion method was used for this purpose. The study found that increasing the Nusselt number led to an increase in energy efficiency, but also caused a drop in outlet temperature at any solar radiation. The mass flow rate (MFR), with larger flow rates resulting in better efficiencies, had a significant impact on the double pass air heater's efficiency. Thus, increasing of DPSAH’s length increases its thermal performances and reach its maximum values for L=9m. These findings could be beneficial in selecting the most efficient design parameters for DPSAH.