Thermal and Flow Analysis of Air in a Uniformly Heated Circular Channel with an Inlet Flap Obstruction in Laminar, Transitional, and Turbulent Flow Regimes

Abstract

An experimental investigation has been carried out to study the thermohydraulic performance of air in transitional flow regime in a circular uniformly heated channel fitted with flap obstruction at the inlet. The Reynolds number (Re) varied from 500 to 7,037. The channel is uniformly heated using heat fluxes of 0.5 and 1 kW/m². Three height and width ratios were used as variable parameters. Correlations for predicting the Nusselt number and friction factor were developed. It was found that for a uniformly heated (1 kW/m²) plain channel, the critical Re for the start of transition is 2,752, and the critical Re for transition termination is 3,667. It was also found that placing the flap obstruction at the inlet of the test section results in early start and end of the laminar-turbulent transition. At heat flux of 0.5 kW/m², the transition begins as early as Re = 1,840 and ends at Re = 3,588, and similarly, for a heat flux of 1 kW/m², the transition begins at Re = 1,859 and ends at Re = 3,604. The highest Nusselt number enhancement was reported for hight ratio of 0.75 and width ratio of 0.25 and for a heat flux of 1 kW/m².

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No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Devendra K. Vishwakarma

Devendra Kumar Vishwakarma is a Ph.D. Research Scholar at the Department of Mechanical Engineeering, Birla Institute of Technology and Science, Pilani, Pilani Campus, Rajasthan, India. His research interest includes experimental and numerical heat transfer and pressure drop in laminar, transition, and turbulent flow regime.

Suvanjan Bhattacharyya

Suvanjan Bhattacharyya is an Assistant Professor in the Department of Mechanical Engineering of Birla Institute of Technology and Science Pilani, Pilani Campus, Rajasthan, India. He completed his post-doctoral research in the Department of Mechanical and Aeronautical Engineering from University of Pretoria, South Africa. His research interest lies in CFD in fluid flow and heat transfer, specializing on laminar, turbulent, steady, unsteady separated flows and convective heat transfer, and experimental heat transfer enhancement.

Manoj K. Soni

Manoj K. Soni is an Associate Professor in Mechanical Engineering Department. He is the coordinator of Center for Renewable Energy and Environmental Development (CREED) of Birla Institute of Technology and Science (BITS) Pilani, and also Coordinator of various collaborative Work Integrated Learning Programs (WILP) of BITS Pilani. His research area includes solar energy systems, photovoltaic cells, thermal energy storage systems, energy and exergy analysis of thermal systems, and renewable energy.

John P. Abraham

John P. Abraham is a Professor of Thermal Sciences at the University of St. Thomas, School of Engineering, St. Paul, Minnesota in USA. His research interests include experimental and computational studies of industry-related heat transfer problems. He is a co-founder of the Laboratory for Heat Transfer Practice.