THERMAL SCIENCE

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Experimental investigation and CFD analysis of influence of swirl, arrangement of nozzle, cross section and diameter of jets on heat transfer in multi-jet air impingement cooling

ABSTRACT
Experimental investigation and CFD analysis were performed to study the effects of swirl, nozzle arrangement, cross section of nozzle, number of jets and jet diameter on heat transfer coefficient in multi-jet air impingement cooling for a target surface of 100 ×150 mm size supplied with a constant heat flux of 7666 W/m2.Thenormalized heat transfer coefficient based on unit volume of air is evaluated through measurement of temperature for flow Reynolds number sin the range of 8000 - 22000 with H/D ratios of 1,2,4 and 6.Investigations with and without swirl reveal that among the tested conditions, for 8 mm jets, introducing swirl reduces the heat transfer whereas for 10mm and 12 mm jets, swirl improves the average heat transfer rate. For sets of 12 nozzles configurations, the staggered arrangement for 6 mm and 8 mm nozzles results in higher heat transfer rate than in-line arrangement unlike in 4 mm nozzles where in-line arrangement is better. Heat transfer coefficients for circular, square and triangular cross sections of same flow are a have been compared. Circular cross section offers better heat transfer coefficient for all the tested conditions. For a given number of nozzles, there is an optimum diameter corresponding to maximum value of normalized heat transfer coefficient. The results are corroborated with CFD analysis for a few representative conditions tested.
KEYWORDS
PAPER SUBMITTED: 2017-06-20
PAPER REVISED: 2018-05-21
PAPER ACCEPTED: 2018-06-11
PUBLISHED ONLINE: 2018-09-22
DOI REFERENCE: https://doi.org/10.2298/TSCI170620177C
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