Open Access

ARTICLE

NUMERICAL INVESTIGATIONS ON HEAT TRANSFER AND FLOW STRUCTURE IN A CIRCULAR TUBE WITH VARIOUS SHAPES OF WINGLET VORTEX GENERATORS

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a Department of Mechanical Engineering Technology, College of Industrial Technology, King Mongkut’s University of Technology North Bangkok, Bangkok 10800, Thailand
b Department of Mechanical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand

* Corresponding Author: Email:

Frontiers in Heat and Mass Transfer 2016, 7, 1-16. https://doi.org/10.5098/hmt.7.22

Abstract

The numerical investigations on flow structure, heat transfer characteristic and thermal performance in a circular tube heat exchanger with various shapes of winglet vortex generators are reported. The rectangular winglet vortex generators (RWVG), delta winglet vortex generators (DWVG) and curve winglet vortex generators (CWVG) are inserted in the middle of the test tube on both downstream and upstream arrangements. The effects of blockage ratios; BR = 0.1 – 0.3, with single pitch ratio (PR = 1) and flow attack angle (α = 30o) on thermal performance are studied for the Reynolds numbers; Re = 100 – 2000. The numerical results are presented in terms of flow and heat transfer patterns; tangential velocity vectors, temperature distributions, local Nusselt number distributions, and compared with the smooth tube. As the results, it is found that the use of the winglets performs higher heat transfer rate, friction factor and thermal performance higher than the smooth tube for all cases. The rise of BR and Re leads to enhance on both the heat transfer rate and friction loss due to the stronger vortex flow. The RWVG provides the highest heat transfer rate and friction loss, while the DWVG gives the reversed result. The downstream arrangement produces higher heat transfer rate than the upstream. In addition, the thermal enhancement factor is found to be maximum at BR = 0.2, Re = 1000, for RWVG with pointing downstream around 2.52.

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