Cross-flow Effect on Flow and Heat Transfer Characteristics of Impinging Jets in

a Confined Channel

Makatar Wae-hayee, Perapong Tekasakul and Chayut Nuntadusit

Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai

Songkhla 90112, Thailand

Manuscript received April 28, 2014

Revised May 15, 2014

ABSTRACT

The flow and heat transfer characteristics of impinging jets with cross-flow effect were investigated for single impinging jet, a row of impinging jets and an array of impinging jets. For case of single impinging jet and a row of impinging jets, the cross-flow was introduced in wind tunnel and flew cross the single jet and row of jets. The jet velocity was fixed corresponding to Re=13400, and cross-flow velocity were varied corresponding to velocity ratio (jet velocity/cross-flow velocity), VR=3, 5 and 7. For array of impinging jets, the jets from 4 rows × 6 columns was studied in the confined channel for inline and staggered arrangement. The jet Reynolds number for each orifice was fixed at Re=13,400. The jet-to-jet distance was fixed at S/D=3, and jet-to-plate distance was fixed at H/D=2(D is 13.2 mm of orifice diameter).For single impinging jet and row of impinging jets, it was found the local heat transfer at impingement regions for the high cross-flow velocity are higher than that the low one. This result attributes from high momentum that impinge on target surface and high turbulence intensity distribution on the surface. For array of impinging jets, it was found that the heat transfer rate of jet with inline arrangement is higher than those the staggered one. The cross-flow can easily pass through the gaps between the rows of inline jets, whereas it appears to be directly blocked by the downstream jet for the case of staggered arrangement. 

Keywords: Impinging jets, Cross-flow, Heat transfer characteristics, Flow characteristics, Thermochromic liquid crystal, Flow visualization, CFD

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