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Performance assessment of solar air heater duct roughened with perforated-winglet vortex generators

 Author(s):Narin Koolnapadola, Pongjet Promvongeb, Sompol Skullongc
aDepartment of Automotive Mechanical Engineering, Faculty of Industrial Technology Rajabhat Rajanagarindra University, Chachoengsao, Thailand

bDepartment of Mechanical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, Thailand
cDepartment of Mechanical Engineering, Faculty of Engineering at Sriracha, Kasetsart University Sriracha Campus, 199 M.6, Sukhumvit Rd., Sriracha, Chonburi, Thailand
International Journal of Smart Grid and Clean Energy, vol. 6, no. 1, January 2017: pp. 31-39
ISSN: 2315-4462 (Print)
ISSN: 2373-3594 (Online)
Digital Object Identifier: 10.12720/sgce.6.1.31-39

Abstract:An experimental study has been conducted to investigate heat transfer, friction loss and thermal performance characteristics of turbulent flow in a solar air heater channel artificially roughened on one side (absorber plate) with multiple perforated-winglet vortex generator (PWVG). Air as the working fluid enters the test duct having a uniform surface heat-flux with Reynolds number (Re) ranging from 5200 to 24,000 in the present work. Effects of four  different punched hole/pore diameters of winglet (d=2 mm, 4 mm, 6 mm and 8 mm) at a single relative winglet height (RB=b/H=0.6), relative winglet pitch (RP=P/H=3) and attack angle (β = 60°) on thermal characteristics are examined. The experimental results show that the PWVG provides the drastic increase in Nusselt number (Nu) and friction factor (f) values over the flat/smooth channel. In addition, substantial increases in Nu and f values are found for the rise in hole sizes. The maximum Thermal Enhancement Factor (TEF) is found for the pore diameter of 2 mm at lower Reynolds number. The present results are also compared with the results from the typical or solid winglet, TWVG (non-punched hole of winglet).

Keywords: Absorber plate; V-baffle; vortex generator; solar air heater; thermal performance

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