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Cold Zone Exploration Using Position of Maximum Nusselt Number for Inclined Air Jet Cooling

Ingole S. B., Sundaram K. K.

Archive of Mechanical Engineering

2017

Vol. LXIV, nr 4

533--549

Inclined jet air cooling can be effectively used for cooling of electronics or other such applications. The non-confined air jet is impinged and experimentally investigated on the hot target surface to be cooled, which is placed horizontally. Analysis and evaluations are made by introduction of a jet on the leading edge and investigated for downhill side cooling to identify cold spots. The jet Reynolds number in the range of 2000 ≤ Re ≤ 20 000 is examined with a circular jet for inclination (θ) of 15 less than θ less than 75 degree. Also, the consequence of a jet to target distance (H) is explored in the range 0.5 ≤ H/D ≤ 6.8. For 45 degree jet impingement, the maximum Nusselt number is widely spread. Location of maximum Nusselt number is studied, which indicates cold spots identification. At a higher angle ratio, the angle is the dominating parameter compared to the Reynolds Number. Whereas at a lower angle ratio, the inclined jet with a higher Reynolds number is giving the cooling point away from leading edge. It is observed that for a particular angle of incident location of maximum Nusselt Number, measured from leading edge of target, is ahead than that of stagnation point in stated conditions.

Experimental investigation of a liquid film formed by impingement of an axisymmetric jet on a flat heated surface

Bykuć S.

Turbulence : international journal

2005

Vol. 11

235-237

The aim of the present work was to study experimentally hydrodynamic and heat transfer characteristics of the flow of a liquid film over a surface. A round jet of water impinging vertically on a horizontal plane forms a thin film flowing radially until the sudden increase of depth occurs (hydraulic jump). During the experiment, the temperature of the solid surface and liquid film thickness in the suhcritical region (downstream of the hydraulic jump) and supercritical region (upstream of the hydraulic jump) were measured. Radial film thickness and Nusselt number distributions were achieved. Experiments were performed for a range of flow rates between 0.3 and 0.8 I/min. The liquid film thickness upstream of the hydraulic jump was an order of magnitude smaller than that of the subcritical region. With the growth of the flow rate, the radius of the hydraulic jump and film thickness after the jump, increased. It was found that the local Nusselt number reached maximum near the stagnation region and decreases gradually with radius as the flow moves downstream with the biggest drop corresponding to the location of hydraulic jump. Downstream of the jump, Nu was approximately uniform. Higher Nusselt numbers were reached for higher flow rates. These differences for various flow rates were much bigger in the supercritical region than that in the subcritical one.