A COMPUTATIONAL STUDY OF HEAT TRANSFER UNDER TWIN TURBULENT SLOT JETS IMPINGING ON PLANAR SMOOTH AND ROUGH SURFACES

摘要

The flow and heat transfer characteristics of twin turbulent slot jets impinging on planar smooth and rough surfaces are examined using a computational fluid dynamics model. The interaction between jets lowers the heat transfer performance of each jet in the zone where the wall jets collide. A single jet performs better than the equivalent twin jet. The average heat transfer under twin jets which are injected alternately so that each one of the pair of jets behaves like a single jet, is found to be better than twin jets issuing simultaneously. It is proposed that alternating jet flows in the twin jet arrangement is a simple novel way to enhance thermal performance of jet pairs. Along with parametric studies of the key flow and geometric parameters, effects of large temperature differences between the jet air and the target surface being heated, and model roughness of the target surface are also evaluated. Interestingly, roughness can lower the heat transfer performance in the impingement zone as the fluid can get trapped in the valleys in the rough surface.