Enhancement of heat transfer by flowing turbulent jet on a linearly decaying (LD) wavy wall

Abstract

The influence of a partial linearly decaying (LD) wavy wall on different fluid flow and thermal parameters has been investigated for the turbulent jet. For the present study, a segment of wall from the leading edge is made with a constant amplitude 0.8a (a = nozzle height), followed by a segment of LD wavy wall. In the region of LD wavy wall, the amp (amplitude) of wavy wall is linearly reduced from 0.8a amplitude to 0a in the downstream direction. The LD wavy wall segment varies from 100% to 0%. For 100% LD wavy wall, the whole wall is made of linearly decaying amplitude, whereas for, 0% LD wavy wall, the whole wall is made wavy with a constant amplitude. The Reynolds number at the inlet is same for all the cases, i.e. 15,000 to maintain the fully turbulent condition at the exit of nozzle. The problem is solved numerically using k−ε RNG model. The results obtained from this study show that for 100% LD wavy wall the velocity decay is minimum and as the % of LD wavy wall decreases, the velocity decay increases. Whereas the thermal decay of jet is maximum in the case of 100% LD wavy wall. Similarly, Ymax, YTmax, and the velocity and thermal jet spread are found to be minimum for the 100% LD wavy wall and all these parameters increase as the % of LD wavy wall decreases. The maximum increment in the heat transfer rate is 27.9% for 100% LD wavy wall in regards to the baseline case (plane wall). However, the maximum increment in thermal hydraulic performance (THP) is noticed for the wavy wall with 50% LD wavy wall, which is equal to 6.7%. In a previous study (ArchanaKumari, 2021 [1]), the increment of 19.0% and 5.3% is observed for the heat transfer and THP respectively. In the present study by introducing LD wavy wall, the increment in the heat transfer and THP are quite significant.