The influence of surface heating on the flow dynamics within a transpired air collector

Abstract

An experimental study was conducted to examine the air flow behavior in the channel of a transpired air collector under different heating conditions. Velocity fields were measured using Particle Image Velocimetry (PIV). Mean velocities and turbulent properties were computed and evaluated. Results show that at high flow rates, the flow was dominated by forced convection while at the lowest flow rate the flow was primarily buoyancy driven, where buoyancy-induced stabilities and heating effects were strongest. It was observed that the buoyancy-induced instabilities enhanced the magnitude and modified the structure of mean and turbulent properties as compared to the unheated flow. The flow rate influenced the relative magnitudes of the normalized mean and turbulent velocities that were enhanced with a decrease in the flow rate at a given heating condition. Collector efficiencies up to 70% were observed, which could be attributed to the corrugation surface geometry that enhanced turbulence and provided a larger heat transfer surface area.