Wall inclination effect in heat transfer characteristics of a combined wall and offset jet flow

Hnaien, Nidhal; Marzouk, Salwa; Aïssia, Habib Ben; Jacques, Jean

doi:10.1016/j.ijheatfluidflow.2017.01.010

Cited by 24 publications

(6 citation statements)

References 16 publications

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“…On the other hand, a decrease in the recirculation zone dimension is observed for higher OJEA values. This is similar to the WOJ flow behavior detected in our previous investigations on parallel jet flow and combined wall and offset jet flow (Nidhal et al [1], [2] and [19]).…”

Section: Mean Flow Structuresupporting

confidence: 90%

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Offset jet ejection angle effect in combined wall and offset jets flow: numerical investigation and engineering correlations

Hnaien

Marzouk

Kolsi

et al. 2019

J Braz. Soc. Mech. Sci. Eng.

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The present paper deals with a numerical study of turbulent flow which combines a wall jet and parallel offset jet. A parametric study was presented to pick out the offset ratio as well as the offset jet ejection angle influence on the merge point, combined point, upper vortex center and lower vortex center positions. Empirical correlations have been provided as a function of the offset ratio and the ejection angle. The main results obtained from the present investigation show that increasing the ejection angle displaces the merge point, the combined point and the vortices centers more upstream along the axial direction which accelerate the merging process launching. Furthermore, for higher value of the ejection angle, these mentioned points approach the horizontal wall along the lateral direction. Keywords Finite volume • Combined jets • Ejection angle • Merge point • Offset ratio List of symbols d Nozzle width (m) Greek symbols Kinematic viscosity (m²/s) Fluid density (kg/m 3) Offset jet ejection angle (OJEA) Subscripts 0 Exit value (at the nozzle exit) a Ambient value m Maximum value t Turbulent value Abbreviations WOJ Wall offset jet LWJ Lower wall Jet UOJ Upper offset jet SOJ Single offset Jet UVC Upper vortex center LVC Lower vortex center MP Merge point CP Combined point OJEA Offset jet ejection angle

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Section: Mean Flow Structuresupporting

confidence: 90%

“…The turbulent jet flow has always attracted the attention of many researchers [1][2][3][4][5]. Combined wall and offset jet flow ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Offset jet ejection angle effect in combined wall and offset jets flow: numerical investigation and engineering correlations

Hnaien

Marzouk

Kolsi

et al. 2019

J Braz. Soc. Mech. Sci. Eng.

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“…Later, Hnaien et al 15 investigated the thermal characteristics of a dual jet with an oblique wall. They noticed that an increase in oblique angle resulted in a decrease of Nusselt number.…”

Section: Introductionmentioning

confidence: 99%

CFD Investigation of Thermal Characteristics for a Dual Jet with a Parallel Co-flow

et al. 2022

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A combined turbulent wall jet and offset jet (also known as the dual jet) with and without the presence of a parallel co-flow stream is studied. The standard k –ω turbulence model is used to predict the turbulent flow. The study focuses on the effects of the co-flow velocity (CFV) on the heat-transfer characteristics of the dual jet flow with the bottom wall maintained at a constant wall temperature. The CFV is varied up to 40% of the jet inlet velocity, and the height of the offset jet is varied from 5 to 11 times the jet width with the inlet Reynolds number taken as 15,000. The heat-transfer results reveal that the local Nusselt number ( Nu x ) along the bottom wall exhibits a peak at the immediate downstream of the nozzle exit, followed by a continuous decay in the rest of the converging region before showing a small rise for a short streamwise distance in the merging region. Further downstream, in the combined region, Nu x gradually decreases with the downstream distance. Except the merging region, no influence of co-flow is observed in the other two flow zones (converging and combined regions). In the merging region, for a given offset ratio (OR), Nu x remains nearly constant for a certain axial distance, and it decreases as the CFV increases. As a result of the increase in the CFV, the average Nusselt number decreases, indicating a reduction in overall convective heat transfer for higher values of the CFV. A regression analysis among the average Nusselt number ( ), CFV, and OR results in a correlation function in the form of within the range OR = 5–11 and CFV = 0–40%.

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“…The offset ratio was fixed to 2.5 and 5. The Reynolds number was set to 53,200. They considered the oblique angle (a) in the range of 0 À40 .…”

Section: Introductionmentioning

confidence: 99%

“…They proposed the correlation for average Nusselt number for various offset ratios and Reynolds numbers for different regions. Further, Hnaien et al 53 also investigated heat transfer characteristics of an oblique dual jet for offset ratio 20. Both constant wall temperature and constant heat flux boundary conditions were considered.…”

Section: Introductionmentioning

confidence: 99%

Effect of wavy wall surface on flow structure and thermal characteristics of a turbulent dual jet comprising of a wall jet and an offset jet

Singh

Kumar

Satapathy

2020

Proceedings of the Institution of Mechanical Engineers, Part A:

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The fluid flow and thermal characteristics of the dual jet are explored numerically. The dual jet is considered with a wavy wall surface having various amplitudes varying between 0.1 and 0.7 with a fixed number of cycles equal to 10. The offset ratio is also varied from 3 to 15 with an interval of 2. The Reynolds number and Prandtl number are set to 15,000 and 0.71, respectively. The Semi Implicit Method for Pressure Linked Equation algorithm is utilised to link the pressure to the velocity. To solve the set of linear algebraic equations Strongly Implicit procedure solver is used. The heat transfer characteristics of the wavy wall surface were studied for two cases: (1) isothermal bottom wall and (2) adiabatic bottom wall. It is found that the wavy wall affects the flow field and heat transfer characteristics drastically. The minimum pressure inside the domain is not found to occur at the vortex centre for all the offset ratios, which is the case of a dual jet with a plane wall. Results also reveal that as the amplitude of the wavy surface increases both local Nusselt number and local heat flux increase near the exit of the nozzle for each offset ratio. Further, it is also noticed that the average Nusselt number increases up to amplitude A = 0.5. Thereafter, it decreases with further increase in the amplitude of the wavy surface. It is found that the wavy surface increases the average Nusselt number by a maximum of 17.6% as compared to the plane wall case.

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Wall inclination effect in heat transfer characteristics of a combined wall and offset jet flow

Cited by 24 publications

References 16 publications

Offset jet ejection angle effect in combined wall and offset jets flow: numerical investigation and engineering correlations

Offset jet ejection angle effect in combined wall and offset jets flow: numerical investigation and engineering correlations

CFD Investigation of Thermal Characteristics for a Dual Jet with a Parallel Co-flow

Effect of wavy wall surface on flow structure and thermal characteristics of a turbulent dual jet comprising of a wall jet and an offset jet

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