Multi-objective design optimization of solar air heater for food drying based on energy, exergy and improvement potential

Abstract

Solar air heaters (SAHs) are commonly utilized in different applications due to their simple structure and low setup cost. Optimizing operating parameters of the SAH is highly linked to the desired application. The aim of this study is to determine the optimal geometric and operational parameters of finned SAH for food drying. In order to achieve this goal, response surface methodology was combined with an experimentally validated thermal model of the SAH system. Multi-objective optimization is carried out according to energy-exergy analysis, improvement potential (IP) and outlet temperature suitable for food drying (40–70 °C). Length/width ratio (L/W) (1–5), height of air duct (0.02–0.2), and number of fins (0-60) were the operating variables. The experimental tests were carried out on the indirect type solar dryer composed of SAH and the drying chamber. The developed code led to consistent numerical results that have been confirmed by experimental tests. The optimal parameters were defined as 1.28 L/W, 0.067 m air duct height and 49 fins. In these optimal conditions, the outlet temperature, thermal efficiency, and IP were 52 °C, 51.78% and 1397.34W, respectively. The optimal design improved the thermal efficiency by 15.76% and IP by 19.33%.