A Critical Review of All Mathematical Models Developed for Solar Air Heater Analysis

Abstract

In this paper, three mathematical models to predict the air collector temperature are reviewed and analyzed. These three models were drawn from 30 publications between 1980 and 2022. The models include lumped model (model 1), a one-dimensional (1D) steady model (model 2), and 1D unsteady model (model 3). The models are established based on the energy balance of the heat exchanger surfaces and the airflow. Solution techniques for models are presented using a system of linear equations, numerical integral, and finite difference method. The results of the sensitivity analysis of the models indicate that the temperatures of the air exiting the collector are similar. Model 3 considers the thickness of the glass cover, absorber plate, and bottom plate thus having the effect of thermal inertia in the morning and afternoon. The maximum difference of outlet air temperature between models 1 and 2 is 0.18 K. The highest outlet air temperature deviation of 0.77 K between models 1 and 3 occurred at 8 AM. When the thicknesses are negligible, the temperature distribution along the air collector of models 2 and 3 is the same. In other words, model 3 should be used when there is the presence of the thickness of the plates and the glass cover.