Effect of Entrance Geometry on Heat Transfer in a Rib-Roughened Rectangular Channel

Abstract

The effect of the entrance geometry conditions on the local and average heat transfer coefficient in a rectangular channel with 45° angled ribs has been investigated. Ribs were deployed on one side only, the remaining walls of the channel being assumed smooth and unheated. The influence of entrance conditions was addressed by considering either a long ribbed unheated section or a smooth channel upstream of the ribbed heated section. As known, channels with 45° angled ribs are characterized by spanwise variations of heat transfer coefficient due to secondary flows, with high heat transfer levels close to one side and low heat transfer levels on the opposite side. Numerical results, checked against experimental data, showed that heat transfer coefficients of first modules are affected by entrance conditions, especially in the most effective heat transfer region. Regardless of entrance condition, a quasi-periodically fully developed heat transfer condition is attained only in the low heat transfer region, while elsewhere heat transfer coefficient distributions are periodic in shape but values tend to increase with the streamwise coordinate. These findings indicate that heat transfer experiments on ribbed channels should be generally accompanied by a careful description of the entrance conditions assumed in the experiments.

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Notes on contributors

Francesca Satta

Francesca Satta is an associate professor of Fluid Machinery and Aeronautical Propulsion at the University of Genoa, Italy. She got a degree in Mechanical Engineering and a Ph.D. in Fluid Machinery Engineering at the University of Genoa. Her research activity is focused on the improvement of the performance of gas turbine components, with particular attention paid to the turbines for aeronautical applications.

Giovanni Tanda

Giovanni Tanda is a full professor of Engineering Thermodynamics and Heat Transfer at the University of Genoa, Italy. He received his degree in Mechanical Engineering from the University of Genoa, Italy and a Ph.D. from the City University, London, U.K. His current areas of research include experimental and numerical heat transfer applied to the cooling technology of gas turbine blades and electronic equipment.

Giulio Venturino

Giulio Venturino is a Ph.D. student in engineering of turbomachinery, energy, environment and transportation systems at the University of Genoa, Italy. Before beginning his Ph.D., he was graduated in Mechanical Engineering – Energy and Aeronautics at the University of Genoa, Italy. His research interests concern the heat transfer effects in gas turbines and secondary flow analysis in aeroengines. Those activities are mainly conducted by numerical analysis.