539 / 2019-01-08 01:24:26

HEAT TRANSFER ENHANCEMENT FOR ARRAY OF IMPINGING JETS WITH SOME BAFFLE ATTACHMENTS

Impinging jets, Heat transfer enhancement, V-shaped baffles Thermochromic liquid crystal, CFD

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The aim of this research is to study the effect of mounting baffles on heat transfer enhancement for array of impinging jets within cross-flow. Array of air jets was directly discharged from round orifices with on inline arrangement and impinged on the inner surface of the rectangular channel. The orifice diameter (D) was 13.2 mm, jet-to-impingement surface distance and jet-to-jet distance were fixed at H=2D and S=3D, respectively. The jet velocity was fixed at 15 m/s (Re=13,400). A pair of rectangular baffles each with length of 1.3D, height of 0.6D and thickness of 3 mm was attached in a V-shaped arrangement on the surface on the upstream side of each impinging jet. The angle of attack was defined as an angle between the baffle to the cross-flow and was varied to give θ=30, 45 and 60 degree. The heat transfer characteristic was visualized by using a Thermochromic Liquid Crystal sheet (TLCs) and the Nusselt number was evaluated by using image processing method. Numerical simulation was also employed to investigate the flow field. The results show that the heat transfer rate for the case with baffle attachment at θ=60 degree is higher than the case of no baffle attachment. This is due to the baffle attachment promoting the turbulence intensity in the jet flow before impingement.