Heat Transfer and Fluid Flow Characteristics in a Swirling Impinging Jet

Senda, Mamoru; Toyoda, Daisuke; Sato, Shigemasa; Inaoka, Kyoji

doi:10.1299/kikaib.70.1828

Cited by 4 publications

(12 citation statements)

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“…For a swirl num ber of 5 = 0 a local minimum in th e h eat transfer is noted at the stagnation point although in this case it is slightly higher th an the stagnation point Nusselt num ber for the non-swirling jet. As the level of swirl is increased, the stagnation point Nusselt num ber drops, for all heights exam ined, and the location of the m axinmm Nusselt num ber moves away from th e stagnation point indicating the spread of the fluid flow as identified by Senda et al [71]. T he drop in heat transfer at the stagnation point can be associated with the outw ard spread of the fluid as the swirl num ber increases, as noted by Senda et al [71], however the prim ary reason can be attrib u ted to the central core of the swirl generators causing a blockage.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 59%

“…As the level of swirl is increased, the stagnation point Nusselt num ber drops, for all heights exam ined, and the location of the m axinmm Nusselt num ber moves away from th e stagnation point indicating the spread of the fluid flow as identified by Senda et al [71]. T he drop in heat transfer at the stagnation point can be associated with the outw ard spread of the fluid as the swirl num ber increases, as noted by Senda et al [71], however the prim ary reason can be attrib u ted to the central core of the swirl generators causing a blockage. The generators were positioned at th e leading edge of the je t nozzle, which denied the separated fiow stream s space to recombine and consequently created m ultiple flow stream s instead of one singular swirling flow.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 59%

“…Since th e Reynolds num ber for this study was nearly four times higher th an th a t of Senda et al [71], the heat transfer m agnitudes vary b u t th e same trends in the Nusselt num ber distributions appear. For a swirl num ber of 5 = 0 a local minimum in th e h eat transfer is noted at the stagnation point although in this case it is slightly higher th an the stagnation point Nusselt num ber for the non-swirling jet.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 60%

“…A similar investigation was conducted by Lee et al [72], exam ining th e sam e swirl numbers as Senda et al [71] b u t w ith the addition of one higher swdrl num ber, 5=0.77.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 74%

“…Senda et al [71] 2.4. Im p in g in g J e t H e a t T r a n s f e r <1, indicating an outw ard spread in the fluid flow.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 99%

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Heat Transfer Characteristics of Swirling Impinging Jets

Brown

Murray

Persoons

et al. 2009

Volume 9: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B and C

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Impinging jets are used in a wide number of industrial cooling applications due to their high heat and mass transfer abilities. The current research is concerned with the effect of swirl on the heat transfer characteristics of jet impingement cooling. Two inserts were designed order to generate swirling flow. These two designs, “Swirl Insert A” and “Swirl Insert B”, were tested at various Reynolds numbers, between 8000 and 16000 inclusive, and at H/D = 0.5 and 1. The jet was directed downwards onto a 25μm thick stainless steel foil which was ohmically heated. Images were recorded using a thermal imaging camera focused on the underside of the foil. These images were then analysed using Matlab and the Nusselt number profile was obtained. It was found that, while both swirl inserts establish an improvement in the heat transfer by comparison to that of a jet with no swirl, the “Swirl Insert B” design performed better that the “Swirl Insert A” design for high Reynolds number at H/D = 0.5 and consistently for H/D = 1. It was also discovered that, while both the “No Insert” and “Swirl Insert B” results did not change dramatically with an alteration in H/D, “Swirl Insert A” decreased by ∼10%.

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Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 59%

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 59%

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 60%

“…A similar investigation was conducted by Lee et al [72], exam ining th e sam e swirl numbers as Senda et al [71] b u t w ith the addition of one higher swdrl num ber, 5=0.77.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 74%

“…Senda et al [71] 2.4. Im p in g in g J e t H e a t T r a n s f e r <1, indicating an outw ard spread in the fluid flow.…”

Section: Straight Pipe Nozzle Geometry With Axial Vanesmentioning

confidence: 99%

See 3 more Smart Citations

Heat Transfer Characteristics of Swirling Impinging Jets

Brown

Murray

Persoons

et al. 2009

Volume 9: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B and C

View full text Add to dashboard Cite

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Comparative study on heat transfer enhancement by turbulent impinging jet under conditions of swirl, active excitations and passive excitations

Uddin

Younis

2019

International Communications in Heat and Mass Transfer

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This paper reports on computations related to a turbulent jet impinging on a flat surface. The goal was to assess the efficiency of alternative methods for enhancing the heat-transfer rates at the target wall. Three methods were considered, all of which involved the manipulation of the jet flow at exit. These were the imposition of a tangential component of motion simulating the generation of swirl by guide vanes, the forced excitation of the mean flow at predetermined amplitude and frequency, and by the placement of a cylinder across the flow from which vortex shedding occurred. The computations were performed using Large-Eddy Simulations and the results compared with experimental data wherever available. It was found that the selection of active excitation frequency plays an important role in terms of enhancement of heat transfer. On the other hand, the passive excitation of the jet by introducing inserts in the flow causes high pressure drop while the introduction of swirl does not always bring about an appreciable enhancement in the heat transfer rates.

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Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

Rodríguez¹

2011

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The literature indicates that a prismatic-core very high temperature reactor can experience thermal stratification and hot spot issues in the lower plenum (LP). This research hypothesizes that the complex thermalhydraulic phenomena in the LP requires a sophisticated computational fluid dynamics (CFD) code with state-of-the-art turbulence models and advanced swirling jet technology to mitigate the two issues. The primary research goals were to increase the heat transfer and mixing capacity of swirling jets, extend swirling jet theory, and to apply those advancements for the mitigation of the thermalhydraulic issues. First, it was demonstrated that the Fuego CFD code successfully modeled a set of key LP thermalhydraulic phenomena. Thereafter, a helicoid vortex swirl model was developed to investigate the impact of the swirl number (S) on mixing and heat transfer. The development of azimuthal and axial velocities that are solely functions of S permitted the analysis of the central recirculation zone's (CRZ) impact on the LP flow field. At this point, several characteristics were found in common between the helicoid vortex and other axisymmetric, Newtonian, incompressible vortices found in the literature. This observation resulted in a more fundamental understanding of how vortices behave, and which traits can be exploited for the purpose of maximizing heat transfer and mixing. Because the CRZ is a strong function of the azimuthal and axial velocities, shaping those velocity profiles had a substantial impact. Eventually, this led to the discovery that vortices may be expressed as alternating series that expand geometrically with odd exponents. This helped corroborate that the 15 axisymmetric vortices discussed in this research are part of a vortex family with seven common traits. This also led to the development of new vortices that are based on one or two series terms that satisfy the Navier-Stokes equations and conservation of mass. In addition, the impact of Reynolds number and swirl decay were explored in order to further quantify their impact. Finally, the above theories and modeling insights were applied towards a comprehensive set of LP calculations that showed that the swirling jets mitigated the entrainment and hot spot issues, while resulting in a reasonable pressure drop. Contents

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Heat Transfer and Fluid Flow Characteristics in a Swirling Impinging Jet

Cited by 4 publications

References 0 publications

Heat Transfer Characteristics of Swirling Impinging Jets

Heat Transfer Characteristics of Swirling Impinging Jets

Comparative study on heat transfer enhancement by turbulent impinging jet under conditions of swirl, active excitations and passive excitations

Swirling jets for the mitigation of hot spots and thermal stratification in the VHTR lower plenum.

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