Mathematical modelling of heat and hydraulic processes in a solar air heater with a concave air duct absorber

Solar air heaters (collectors) are becoming increasingly popular for both heating and industrial applications due to their cheapness and ease of maintenance. However, how to increase the useful energy and thermal efficiency to be produced per unit area of solar air heaters is among the most basic research topics. In this paper, the design of a solar air heater with concave air tube absorbers was optimized by numerical modelling. For this, the behaviour of concave tube absorbers with different geometrical arrangements has been investigated. Also, in this article, a mathematical model was developed to determine the optimal geometric location of air pipes, and the reliability of the obtained results was verified. According to the simulations carried out, a checkerboard-shaped concave-tube placement on the absorber surface, perpendicular to the airflow, parallel to the airflow, and in the form of a V shape was calculated. The aerodynamically resistance coefficient of the heated air, pressure losses, and temperature changes were taken into account in the selection of geometric indicators. As a result, the situation with the lowest pressure loss was determined in Reynolds number (Re) 2000-10000 in determining the optimum geometrical layout.