Flow around Turbulence Promoters in Parallel Channel, (II)

Abstract

Effects of walls on shedding vortex in developed channel flow were investigated putting a cylinder a t the center of channels or on a wall for the value of wld from 2 to 4. Results were compared with the uniform flow result.When a cylinder was put at the center of the channels, non-dimensional frequency plotted against Reynolds number agreed with the uniform flow result a t low Reynolds number. However, i t increased rapidly with Reynolds number, then it lay considerably above the uniform flow results a t high Reynolds number. When a cylinder was put on a wall, nondimensional frequency was considerably lower than the uniform flow result in the cases Of wld=3 and 4. In the case of w J d = 2 , however, frequency was higher than the uniform flow result a t high Reynolds number. In all cases in the present study, the transition Reynolds number increased with decrease in the value of wld.These results indicate that the increase in shedding frequency was due to the shift in velocity distribution from Poiseuille parabora in the wake region, which obviously increased with Reynolds number and with decrease in channel width.

Enhancing Heat Transfer in Power Transformer Radiators via Thermo-Fluid Dynamic Analysis with Periodic Thermal Boundary Conditions

“…It can be observed in Fig. 10 that, even though a secondary flow is induced on case (16), the temperature field obtained is very similar to that of case (0). Therefore, no significant thermal improvement can be observed in the term mγt f it , and even worse, the volumetric flow is reduced diminishing the FM.…”

“…8 and 9, that the FM of case ( 16) does not improve with respect to that of case (0), regardless the transversal power applied to the fluid. Case (4) has a similar behavior to case (16), i.e., it has an FM below 1 for 0.4 ≤ λ ≤ 1.4.…”

“…Several studies have been conducted to analyze the behavior of different types of turbulators. Shiina [16] performed an experimental study on a cylinder near the walls of a rectangular section channel to generate turbulence, with an application in high-temperature areas of a nuclear reactor. Han et al [17,18] conducted experimental studies on the implementation of rectangular turbulators to increase heat exchange within the cooling ducts of a gas turbine.…”