Natural Heat Convection Analysis on Boundary layer and Apply Utilization to Inclined Solar Collector

Abstract

Natural convection heat transfer driven by solar energy is a sustainable and environmentally friendly method for drying agricultural products, representing a critical mechanism in various solar dryer applications (free energy). This study experimentally investigates the laminar natural convection heat flow along an inclined solar collector under conditions approximating steady-state operation during peak sunlight hours. The research evaluates the velocity and temperature distributions on an inclined glass plate based on the development of thermal boundary layers. In addition to the limiting cases of flow adjacent to surfaces. Results indicate that the natural convection heat transfer coefficient ranges from 5.2 to 6.6 W/m2°C, while the collected heat energy ranges from 150 to 610 J/s, achieving a collector efficiency between 23.9% and 38.3%. The dry air flow rate was observed to be between 0.016 and 0.024 m3/s during daylight hours (local time). Under a fixed solar collector tilt angle of 25° and solar irradiation ranging from 217.8 W/m2 to 552.7 W/m2, the average Nusselt and Rayleigh numbers were determined to be 221.7 and 6.7x109, respectively. Finally, load tests demonstrated a drying rate ranging from 0.07 to 1.45 kg/hr, which varied significantly based on local climatic conditions and the time of day.