Analysis of the thermal performance of a hybrid solar-CHP dryer for drying medicinal plants

There have been a very limited number of studies conducted on utilization of thermal combination from combined solar-CHP systems for drying agricultural products. Most of researches in this field are focused on studying this combination for electricity and heat generation for houses, industrial process heat and so on. In this study, a solar drying system incorporating a fixed bed configuration was implemented for drying the Pennyroyal medicinal plant. The system was enhanced with the integration of a CHP system. For the supply of solar thermal energy, a flat plate collector was employed. This study aimed to investigate the thermal efficiency by evaluating the collector in three distinct modes: collector non-porous (CNP), collector non-section with porous (CNSP) and collector with section and porous (CSP). The fluid velocity and temperature passing over the collector's flat plate were analyzed using CFD methodology and thermal imaging techniques. The findings of the study revealed that the CHP system exhibited satisfactory performance in supplying the supplementary heat required for the solar collector. The CSP mode exhibited the highest values of heat transfer coefficient and heat flux, while the CNP mode showed the lowest values and the greatest variations. The flat plate solar collector thermal efficiency was calculated as 59.67% for the CNP mode, 64.12% for the CNSP mode and 70.3% for the CSP mode. The heat exchanger displayed an overall efficiency of 26% and a heat transfer coefficient of 38.60 W m⁻² °C, representing the highest values achieved in the study.