A New and Efficient Design of Double Pass Solar Air Heater

Document Type : Research Article


1 Mechanical Engineering Department, School of Engineering, Shahid Bahonar University of Kerman, Kerman, Iran

2 Department of Mechanical Engineering, Technical and Vocational University (TVU), Tehran, Iran


In the present study, a new and efficient design of a double-pass solar air heater with converged air ducts is proposed and simulated numerically. In the designed solar collector, the inclined position of the absorber plate regarding the glass cover and bottom plate provides converged shapes for the upper and lower air ducts, in which the accelerated flows and extra turbulence generation cause an increased rate of convection heat transfer. This concept is evaluated by numerical solution of the governing equations for air turbulent flow consisting of the conservations of mass, momentum, and energy by the finite element method using the COMSOL Multi-physics. Besides, the conduction equation is solved to compute the temperature distributions inside all solid parts. Numerical findings reveal that the increased velocity of airflow inside the converged duct causes significant convection enhancement, especially in the downstream side of airflow with a thick thermal boundary layer. This behavior leads to a considerable decrease in the absorber temperature due to a higher convection coefficient. The air outlet temperature for the studied test case with the inclined angle of 3^0 is found 3.5〖 C〗^0 more than that obtained for the base model and the percentage of efficiency increase is calculated about 10% due to using a converged duct.


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