Heat transfer due to impinging co-axial jets and the jets’ fluid flow characteristics

Çelik, Nevin; Eren, Haydar

doi:10.1016/j.expthermflusci.2009.01.007

Cited by 28 publications

(12 citation statements)

References 16 publications

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“…Before discussing the results, the heat transfer values should be mentioned briefly. Table 3 presents the average Nusselt numbers for the considered parameters, H/D (2,6,8,10) and Re (20,000, 40,000). These results have already been published in [22].…”

Section: Design Analysis Of Experimental Resultsmentioning

confidence: 99%

“…[1][2][3][4][5]. In the co-axial jet impingement process the co-axial jet enhances potential core region and turbulence intensity at the nozzle exit due to presence of mixing of primary and secondary flows within [6,7]. The effects of target surface on jet have been analyzed by means of changing the geometry of the target surface such as flat plate, concave, convex, spherical, cylindrical, etc.…”

Section: List Of Symbols Dfmentioning

confidence: 99%

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Design analysis of an experimental jet impingement study by using Taguchi method

Çelik

Turgut

2012

Heat Mass Transfer

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In current study design analysis of a specified impingement jet application is performed by use of Taguchi method. Some results from a previously done experimental study that includes the impingement of co-axial and single circular jets to the both roughened and smooth heated surfaces are handled. By use of Taguchi method, some results are obtained to show the effect of Reynolds numbers (Re = 20,000 and 40,000)

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Section: Design Analysis Of Experimental Resultsmentioning

confidence: 99%

Section: List Of Symbols Dfmentioning

confidence: 99%

Design analysis of an experimental jet impingement study by using Taguchi method

Çelik

Turgut

2012

Heat Mass Transfer

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“…These studies include the effect of change in jet diameter [15,18], jet flow rate [8,9,21], nozzle configuration [18,19], jet exit to surface spacing [14,17], surface initial temperature [2,8,21] etc. Though, few studies for vertical surface have also been observed, however these are primarily with air jet cooling methods [23][24][25]. Moreover, the studies reported for vertical metallic rod with water as coolant are for film cooling method, i.e.…”

Section: Introductionmentioning

confidence: 95%

Rewetting of hot vertical rod during jet impingement surface cooling

et al. 2015

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List of symbolsA Test-surface area (m 2 ) Bi Biot number, hD/2k s CHF Critical heat flux c p Specific heat of the surface material (kJ/kg K) d Jet diameter (m) D Test surface diameter (m) h Heat transfer coefficient (W/m 2 K) k Thermal conductivity (W/m K) l Downstream spatial location on test surface (m) Q Water flow rate (lpm) q Surface heat flux (W/m 2 ) Re Reynolds number (Ud/υ) Rw Rewetting number or dimensionless rewetting velocity (uD/2α) r Radial distance from the stagnation point (m) t Time (s) t d Wetting delay (s) T Temperature (°C) u Rewetting velocity (m/s) v Volume of test-section (m 3 ) z/d Dimensionless nozzle exit to test surface spacing Greek symbols υ Kinematic viscosity of water (m 2 /s) α Thermal diffusivity of surface (m 2 /s) ρ Density of surface material (kg/m 3 ) Subscripts B Bottom side downstream location e Experimental value i Initial value j Jet MFB Minimum film boiling m MaximumAbstract A stainless steel (SS-316) vertical rod of 12 mm diameter at 800 ± 10 °C initial temperature was cooled by normal impinging round water jet. The surface rewetting phenomenon was investigated for a range of jet diameter 2.5-4.8 mm and jet Reynolds number 5000-24,000 using a straight tube type nozzle. The investigation were made from the stagnation point to maximum 40 mm downstream locations, simultaneously for both upside and downside directions. The cooling performance of the vertical rod was evaluated on the basis of rewetting parameters i.e. rewetting temperature, wetting delay, rewetting velocity and the maximum surface heat flux. Two separate Correlations have been proposed for the dimensionless rewetting velocity in terms of rewetting number and the maximum surface heat flux that predicts the experimental data within an error band of ±20 and ±15 % respectively.

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“…However, the effects of the coaxial shape of impinging jets have always remained a raw subject and more investigations on this subject are still required. Some of the rare works or more accurately the only ones were those carried out by Celik et al (2012Celik et al ( , 2009, who studied the heat flux of an impinging coaxial jet for different nozzle diameter ratios. Based on the study findings, the heat transfer on the stagnation zone differs from one case to another.…”

Section: Introductionmentioning

confidence: 99%

Shielding Gas Coaxial Jet Pipes Numerical Study of a Vertical Laser Welding Process of AZ91 Magnesium Alloy

Boughanmi¹,

Bannour²,

Mhiri³

et al. 2018

JAFM

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The laser welding of magnesium alloys, largely used in many fabrication applications, has gained considerable interest especially in aerospace, electronics, automotive industry etc. Unfortunately, this process is associated to an undesired phenomenon which is "oxidation". For this reason, a good shielding system of the welding zone is of major importance. This paper presents a numerical study using computational fluid dynamics (CFD) of a laser welding process employing a moving volumetric heat source. Starting with the turbulence model validity, a parametric study of this welding process in a vertical position aiming to optimize the design of protection gas device, the gas jet inclination, the appropriate welding direction and the gas type is, then, proposed. The optimum parametric combination ensuring the largest gas coverage area is the one where the shielding gas is Argon, supplied by the coaxial nozzles at a downward inclination angle with respect to the laser beam axis, and a downward welding direction.

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Heat transfer due to impinging co-axial jets and the jets’ fluid flow characteristics

Cited by 28 publications

References 16 publications

Design analysis of an experimental jet impingement study by using Taguchi method

Design analysis of an experimental jet impingement study by using Taguchi method

Rewetting of hot vertical rod during jet impingement surface cooling

Shielding Gas Coaxial Jet Pipes Numerical Study of a Vertical Laser Welding Process of AZ91 Magnesium Alloy

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