MODELLING AND UNSTEADY ANALYSIS OF A SOLAR AIR HEATER USING FINITE DIFFERENCE METHOD

Abstract

The solar air heater is a simple device, easy to manufacture and wide applicability, especially in the field of drying. In this study, a system of differential equations was established to find the temperature in the device with respect to time and the direction of air flow. Weather data including solar radiation and ambient temperature with the time of a day are used as input data to the mathematical model. Finite difference technique with implicit method and upwind scheme is employed to discrete the system of partial differential equations. The analysis results show that the characteristics of temperature distribution in the device varies from the morning to the afternoon. Thermal performance also varies with the time and glass thickness. The greatest thermal efficiency is reached at 4 to 5 pm. At the beginning of the day, the thermal efficiency is very low because the solar energy is mainly absorbed by the glass and the absorber. To achieve performance that does not notably change over time, it is necessary to reduce the thickness of the glass and the absorber.