Simulation, design and experimental performance evaluation of an innovative hybrid solar-gas dryer

In this paper, a new configuration of hybrid solar-gas dryer is proposed and designed. Instead of direct heating, as usually used in gas dryers, an original indirect air heater was considered in the proposed configuration where the flue gases exhaust outside the drying chamber avoiding their diffusion in the product. This paper presents a numerical simulation of a hybrid solar-gas dryer operated under forced convection with an air mass flow rate of 0.025 kg/s. Simulations of the chamber temperature and humidity threshold and heat distribution were performed. The thermal efficiency of the dryer operated in solar mode (SM), gas mode (GM) and hybrid mode (HM) was calculated. CFD simulations revealed adequate results for efficient drying of many local products. Experimental and simulation results reveal that the temperature and relative humidity are in the suitable ranges for drying wide kind of agriproducts. Indeed, the average drying temperature and relative humidity ranged between 25°C and 80 °C and 31.3–6.2%, respectively. Simulation and experimental values are very close and the RMSE and RMSE% remained under (2.1 °C, 2.7%) for the temperature and (2.5%, 2.4%) for the relative humidity. The maximum dryer efficiencies were found near 42%, 37% and 40% for SM, GM and HM, respectively.