Thermal performance improvement of a solar air heater fitted with winglet vortex generators. (1st January 2018)

• Record Type: Journal Article
• Authors: Chamoli, Sunil; Lu, Ruixin; Xu, Dehao; Yu, Peng
• Is Part Of: Solar energy. Volume 159(2018)
• Page Start: 966
• Page End: 983
• Publication Date: 2018-01-01
• Subjects: Heat transfer -- Friction factor -- Winglet vortex generator -- Solar air heater -- Numerical simulation; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2017.11.046
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Highlights: WVGs used generate additional secondary flow to promote efficient fluid mixing. High heat transfer occurs at the higher tip edge ratio and at flow angle of 60°. High tip edge ratio and flow angle of 60° also impose large pumping power penalty. WVG inserts shows good thermal enhancement factor with a maximum value of 2.20. Statistical correlations for Nusselt number and friction factor are also developed. Abstract: Numerical simulations are carried out to investigate the thermal and flow characteristics of a solar air heater (SAH) embedded with winglet vortex generator (WVG) for the Reynolds number ( Re ) ranging from 3500 to 16, 000. The geometrical parameters of WVG considered are the tip edge ratio ( c/a ) from 0 to 1 and the angle of attack ( α ) from 30° to 90°, respectively. Computations are based on the finite volume method coupled with the SIMPLE algorithm. The effects of WVG on the dimensionless parameters, Nusselt number ( Nu ), friction factor ( f ), Nusselt number ratio ( Nu / Nu s ), friction factor ratio ( f / f s ), and thermal enhancement factor (TEF) are discussed. Nu and f increase with the initial increase of α from 30° to 60° and then decrease with a further increase in α . The maximum values of Nu and f appears at α = 60° and c/a = 1. The results show that the WVG with c/a = 0 and α = 30° provides the best TEF in the range from 1.72 to 2.20. The internal flow behavior along with the distribution of the temperature field and streamlines is explored to explain the effect of WVG configurations on heat transfer and friction factor, respectively. The modified WVG affects the flow and temperature fields, which leads to a significant enhancement in the convective heat transfer rate.