Flow and heat transfer characteristics of a swirling impinging jet issuing from a threaded nozzle

Xu, Liang; Yang, Tao; Sun, Yanjing; Xi, Lei; Gao, Jianmin; Li, Yunlong; Li, Jibao

doi:10.1016/j.csite.2021.100970

Cited by 20 publications

(8 citation statements)

References 35 publications

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“…In ref. [26], the experimental data shows that heat transfer on the flat target surface for the new nozzle with θ = 45 • can be enhanced on the whole target surface compared with the MCIJ and CIJ. For the MCIJ, the flow feature is different for that of the CIJ, and the heat transfer on the flat target surface is comparable to that of the SIJ [25,26].…”

Section: Problem Description and Computational Setupmentioning

confidence: 87%

“…[26], the experimental data shows that heat transfer on the flat target surface for the new nozzle with θ = 45 • can be enhanced on the whole target surface compared with the MCIJ and CIJ. For the MCIJ, the flow feature is different for that of the CIJ, and the heat transfer on the flat target surface is comparable to that of the SIJ [25,26]. When the target surface becomes concave, the jet flow field for the MCIJ and SIJ is more complex, and heat transfer on a semi-cylinder concave target for these new nozzles may be more interesting.…”

Section: Problem Description and Computational Setupmentioning

confidence: 87%

“…The combination of tangential and axial velocities enhances jet turbulent intensity, and hence it is deemed to have different swirling intensities and correspondingly different jet flow field characteristics. Thus far, lots of new nozzles with (intrusive) geometric inserts or directly guiding tangential flow have been proposed to excite the swirling jet [26], and then there have been no unified understanding of the flow mechanism and flow characteristics of swirling impinging jets (SIJ), and further studies are needed.…”

Section: The Selection Of the Dslm And Wale Modelsmentioning

confidence: 99%

See 2 more Smart Citations

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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Section: Problem Description and Computational Setupmentioning

confidence: 87%

Section: Problem Description and Computational Setupmentioning

confidence: 87%

Section: The Selection Of the Dslm And Wale Modelsmentioning

confidence: 99%

See 1 more Smart Citation

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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“…With the development of electronic equipment in miniaturization and high integration, high heat flux generation poses a greater challenge to the heat dissipation of equipment. There are various potential solutions that have been proposed as potential candidates for electronic cooling, such as impinging jet cooling technology [ 1 , 2 ], heat pipes [ 3 , 4 ], the application of porous materials which can provide a high heat exchange area to volume ratio [ 5 , 6 , 7 ], as well as microchannel heat exchangers. The use of microchannels is one of the most important solutions for the design of compact heat sinks for high heat flux removal.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of the Thermal and Hydraulic Performance of Supercritical CO2 and Water in Microchannels Based on Entropy Generation

Zeng

2022

Entropy

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The excellent thermophysical properties of supercritical CO2 (sCO2) close to the pseudocritical point make it possible to replace water as the coolant of microchannels in application of a high heat flux radiator. The computational fluid dynamics (CFD) method verified by experimental data is used to make a comparison of the thermal hydraulic behavior in CO2-cooled and of water-cooled microchannels. The operation conditions of the CO2-based cooling cases cover the pseudocritical point (with the inlet temperature range of 306~320 K and the working pressure of 8 MPa), and the water-based cooling case has an inlet temperature of 308 K at the working pressure of 0.1 MPa. The channel types include the straight and zigzag microchannels with 90°, 120°, and 150° bending angles, respectively. The analysis result shows that, only when the state of CO2 is close to the pseudocritical point, the sCO2-cooled microchannel is of a higher average heat convection coefficient and a lower average temperature of the heated surface compared to the water-cooled microchannel. The entropy generation rate of the sCO2-cooled microchannel can reach 0.58~0.69 times that of the entropy generation rate for the water-cooled microchannel. Adopting the zigzag structure can enhance the heat transfer, but it does not improve the comprehensive performance represented by the entropy generation rate in the sCO2-cooled microchannel.

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“…Ikhlaq et al (2019) compared both swirling and non-swirling transient flow development. Liang Xu et al (2021) proposed a new swirling impingement cooling jet with four inner spiral grooves in internal threads. They experimentally investigated the heat at different swirl angles from 0 °to 45 °and different Re and jet-toplate distances.…”

mentioning

confidence: 99%

On the impingement of heat transfer using swirled air jets

Kotb

Askar²,

Saad³

2023

Front. Mech. Eng.

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Experimental analyses were conducted under identical experimental conditions on the heat transfer between a constant heat flux flat plate and a round air jet for both conventional and swirled jets. Vane-type swirl generators inserted at the nozzle exit were used to produce a swirl. The experimental measurements were performed at a fixed Reynolds number value (Re = 23,000) calculated on the jet tube’s inside diameter. A comparison between conventional air jets and swirl jets with swirl numbers of S = 0, 0.19, 0.42, and 0.72 was presented for the different nozzle-to-plate spacings Z/D = 2, 6, and 10. The results show that heat transfer to the plate decreases when the nozzle-to-plate distance increases. In addition, increasing the swirl number S increases heat transfer uniformity but decreases global heat transfer. At the low plate-to-jet distance Z/D = 2, the point of maximum heat transfer is shifted to a radial position depending on the swirl number. Also, for both Z/D = 6 and 10, the stagnation point and stagnation region heat-transfer enhances only for swirl numbers 0 and 0.19.

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Flow and heat transfer characteristics of a swirling impinging jet issuing from a threaded nozzle

Cited by 20 publications

References 35 publications

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

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

Comparative Study of the Thermal and Hydraulic Performance of Supercritical CO2 and Water in Microchannels Based on Entropy Generation

On the impingement of heat transfer using swirled air jets

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