Improvement of heat transfer from high heat flux surfaces by using vortex promoters with different geometries and impinging jets


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Kilic M., BAŞKAYA Ş.

JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, cilt.32, sa.3, ss.693-707, 2017 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 32 Konu: 3
  • Basım Tarihi: 2017
  • Doi Numarası: 10.17341/gazimmfd.337616
  • Dergi Adı: JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY
  • Sayfa Sayıları: ss.693-707

Özet

In this study; the enhancement of heat transfer from a surface with constant heat flux using an impinging jet and different shapes of vortex promoters was investigated numerically. Firstly, fluid flow and heat transfer in a channel were investigated for different Reynolds numbers, and ratio of channel height to nozzle hydraulic diameter (H/Dh), without using vortex promoters. Afterwards, effects of cylindrical, square and triangular vortex promoters on fluid flow and heat transfer for ratio of distance of vortex promoter to jet center to nozzle hydraulic diameter were investigated. In the last phase; effects of second group of vortex promoters were investigated on heat transfer and fluid flow. As a result; by using impinging jets and vortex promoters an increase of 28% on heat transfer from the surface can be observed according to the condition without vortex promoter. With increasing Reynolds number an increase on heat transfer was observed. Decreasing the channel height does not increase the heat transfer significantly. For the cylindrical vortex promoters maximum local Nusselt number is obtained at L/Dh=1.4. The most effective heat transfer is obtained with triangular vortex promoters. Using second group of vortex promoters can cause an increase of 36.1 % on heat transfer locally, but cannot cause a prominent increase on heat transfer along the target plate generally. Additionally, it is observed that the low Reynolds k-epsilon turbulent model can represent temperature variation and flow characteristic quite well.