Heat transfer and flow structure of a multichannel impinging jet

Fénot, Matthieu; Dorignac, Eva; Lalizel, Gildas

doi:10.1016/j.ijthermalsci.2014.12.006

Cited by 40 publications

(8 citation statements)

References 30 publications

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“…In fact, it is very frequent to encounter studies in which tangential conduction through the board is neglected or in which the conductance anisotropy is claimed to be negligible (see, eg. [14,[23][24][25]).…”

Section: Heated-thin-foil and Anisotropic Sensorsmentioning

confidence: 99%

Evaluation of anisotropic tangential conduction in printed-circuit-board heated-thin-foil heat flux sensors

Torre

Ianiro

Discetti

et al. 2018

International Journal of Heat and Mass Transfer

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Section: Heated-thin-foil and Anisotropic Sensorsmentioning

confidence: 99%

Evaluation of anisotropic tangential conduction in printed-circuit-board heated-thin-foil heat flux sensors

Torre

Ianiro

Discetti

et al. 2018

International Journal of Heat and Mass Transfer

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“…In recent years, different inserts have been introduced to generate swirling jets and generally include a screw rod, twisted tapes/strips, or a guide vane inside a nozzle which can form a swirl element. Fenot et al [9] employed a screw rod with eight narrow channels with an angle of θ = 0 • or 21 • . They observed that the presence of an insert modified the flow and increased the Nu values in comparison with classical round jet flow only for a small nozzleto-plate distance.…”

Section: Introductionmentioning

confidence: 99%

Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

Xu¹,

Zhao²,

Xi³

et al. 2021

Applied Sciences

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Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

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“…Dae et al et al (2002) examined the Nusselt number variation on a heated surface with swirling impinging jet using vane type swirl generator with swirl number varying from 0 to 0.77 and found better uniformity in heat transfer at higher swirl number Sw = 0.77 reporting that the swirling effect is insignificant at larger nozzle to plate distance (H/D = 10). Fenot et al (2015) conducted heat transfer studies on multi-channel impinging jet by comparing heat transfer distribution from a hot jet issued from a circular nozzle and a swirling nozzle with Sw = 0 and 0.26. They reported that the Nusselt number increases for the swirling impinging jet at lower separation distance (H/D =1) and it decreases with increasing separation distance (H/D = 6) compared with circular jet.…”

Section: Introductionmentioning

confidence: 99%

Experimental Analysis of Heat Transfer and Multi Objective Optimization of Swirling Jet Impingement on a Flat Surface

Illyas

Bapu²,

Rao

2019

JAFM

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The influence of swirling flow on distribution of wall heat transfer on a flat plate with helicoid swirl inserts is experimentally studied. The focus of the study is on the swirling effect imposed by helicoid surfaces. Six helicoid swirl inserts of single vane, double vanes and triple vanes with swirl number (Sw) of 0.75 and 1.1 are used in this study. The heat transfer measurements are made for the Reynolds number range of 12700 -32700 and for the nozzle exit to impinging plate distance (H/D) of 1, 2, 3 and 4 using thermo chromic liquid crystal technique. The swirling impinging jet is also compared with circular impinging jet on the heat transfer performance. The obtained experimental results provide the information on the behavior of single, double and triple helicoid swirl inserts on the heat transfer performance. The experimental values are analyzed with multi objective optimization technique of principle component analysis by computing multi response performance index (MRPI). Their performance is presented in terms of heat transfer rate through evaluation of Nusselt number on the impinging surface and heat transfer uniformity and decay of Nusselt number. The principle component analysis reveals that the double helicoid with higher H/D ratio improves performance of the swirling jet with relatively higher computed MRPI. It is found from the analysis of variance (ANOVA) that the H/D ratio contributes significant effect on the output followed by number of helicoid vanes and swirl number.

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Heat transfer and flow structure of a multichannel impinging jet

Cited by 40 publications

References 30 publications

Evaluation of anisotropic tangential conduction in printed-circuit-board heated-thin-foil heat flux sensors

Evaluation of anisotropic tangential conduction in printed-circuit-board heated-thin-foil heat flux sensors

Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

Experimental Analysis of Heat Transfer and Multi Objective Optimization of Swirling Jet Impingement on a Flat Surface

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