Numerical and experimental investigation of a solar air heater duct with circular detached ribs to improve its efficiency

Abstract

A solar air heater duct (SAH-duct) SAH-duct has low thermal performance due to the low heat transfer coefficient of air which is the working fluid. Proper mixing of relatively hot and cold air with respect to the hot absorber plate of the SAH-duct can enhance heat transfer. It can be achieved by placing suitable hindrances in the path of airflow like detached ribs. This study presents the numerical investigation of an asymmetrically heated 2D rectangular SAH-duct with in-line arranged circular detached ribs. In the geometrical configurations of the detached ribs; blockage ratio d/H, clearance ratio c/d, and relative longitudinal pitch ratio P/d are varied as 0.04–0.48, 0.1–1.2, and 05–50 respectively at Reynolds number Re 3000–15000 to study their effect on the thermal-hydraulic performance of the SAH-duct. Local and space-averaged thermal-fluid properties like heat transfer coefficient, and friction factor, Nusselt number, pressure coefficient, etc. are discussed through the graphical illustrations and contour plots. The various dimensions of the ribs are varied to find the optimum geometrical configuration of the detached ribs.

Keywords

• Solar air heater
• Detached ribs
• Heat transfer enhancement