Numerical Study on Stagnation Point Heat Transfer by Jet Impingement in a Confined Narrow Gap

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Y. Q. Zu ◽  
Y. Y. Yan ◽  
J. Maltson
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Computational Cost ◽  
Jet Impingement ◽  
Diameter Ratio ◽  
Eddy Simulation ◽  
Plate Length ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
Target Spacing

In this paper, the heat transfer characteristics of a circular air jet vertically impinging on a flat plate near to the nozzle (H/d=1–6, where H is the nozzle-to-target spacing and d is the diameter of the jet) are numerically analyzed. The relative performance of seven turbulent models for predicting this type of flow and heat transfer is investigated by comparing the numerical results with available benchmark experimental data. It is found that the shear-stress transport (SST) k−ω model and the large Eddy simulation (LES) time-variant model can give better predictions for the performance of fluid flow and heat transfer; especially, the SST k−ω model should be the best compromise between computational cost and accuracy. In addition, using the SST k−ω model, the effects of jet Reynolds number (Re), jet plate length-to-jet diameter ratio (L/d), target spacing-to-jet diameter ratio (H/d), and jet plate width-to-jet diameter ratio (W/d) on the local Nusselt number (Nu) of the target plate are examined; a correlation for the stagnation Nu is presented.

Modelling of Impinging Flow and Heat Transfer in a Confined Narrow Gap

2008 ◽  
Author(s):  
Y. Q. Zu ◽  
Y. Y. Yan
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Large Eddy Simulation ◽  
Diameter Ratio ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
Shear Stress Transport ◽  
Large Eddy ◽  
Target Spacing

In this paper, the flow and heat transfer characteristics of a circular air jet vertically impinging on a flat plate near to the nozzle (H/d = 1∼6, where H is the nozzle-to-target spacing, d the diameter of the jet) are numerical analyzed using the CFD code FLUENT 6.1.18. The relative performance of seven versions of turbulent models, including the standard k–ε model, the renormalization group k–ε model, the realizable k-ε model, the standard k–ω model, the Shear-Stress Transport (SST) k–ω model, the Reynolds Stress (RS) model and the Large Eddy Simulation (LES), for the prediction of this type of flow and heat transfer is investigated by comparing the numerical results with available benchmark experimental data. It is found that Shear-Stress Transport k–ω model and Large Eddy Simulation time-variant model can give better predictions of fluid flow and heat transfer properties; especially, the SST k–ω model is recommended as the best compromise between the computational cost and accuracy. Using SST k-ω model, the effects of jet Reynolds number (Re), jet plate length-to-jet diameter ratio (L/d), target spacing-to-jet diameter ratio (H/d) and jet plate width-to-jet diameter ratio (W/d) on local Nusselt number (Nu) of the target plate are examined. A correlation for the stagnation Nu is presented.

Selection of CFD Turbulence Model for the Application of Submerged Multi-Air Jet Impingement

2011 ◽  
Author(s):  
Nagesh K. Chougule ◽  
Gajanan V. Parishwad ◽  
Sachin Pagnis ◽  
Prashant R. Gore ◽  
Chandrashekhar M. Sewatkar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Computational Cost ◽  
Jet Impingement ◽  
Turbulent Jets ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Air Jet

Most impinging jet industrial applications involve turbulent flow in the whole domain downstream of the nozzle, and modeling turbulent flow presents the greatest challenge in the effort to rapidly and accurately predict the behavior of turbulent jets. Numerical modeling of impinging jet flows and heat transfer is employed widely for prediction, sensitivity analysis, and device design. Finite volume computational fluid dynamics (CFD) models of impinging jets have succeeded in making good predictions of heat transfer coefficients and velocity fields. The difficulties in accurately predicting velocities and transfer coefficients stem primarily from modeling of turbulence and the interaction of the turbulent flow field with the wall. In present work, the flow and heat transfer characteristics of circular multi jet array (3×3) of 5mm diameter impinging on the Flat plate heat sink are numerically analyzed based on the CFD commercial code ANSYS CFX. The relative performance of four different turbulence models, including Standard k-ε, RNG k-ε, (Renormalization Group), Standard k-ω and SST (Shear-Stress Transport) k-ω models are done for the prediction of this type of flow and heat transfer is investigated by comparing the numerical results with experimental data. It is found that SST k-ω model gives better predictions with moderate computational cost. Using SST k-ω model, the effect of Reynolds number (Re) on the average Nusselt number (Nua) of target plate is examined at Z/d = 6 (Z/d is the gap between nozzle exit and target surface).

Numerical Modeling of Turbulent Flow and Heat Transfer Within a Bayonet Tube

2007 ◽  
Author(s):  
Feng Sun ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Experimental Result ◽  
Working Fluid ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
The Impact

This paper presents a numerical study of turbulent flow and heat transfer in a bayonet tube under steady state. First, various turbulent models and wall treatment methods have been tested and validated against the experimental result from a turbulent air jet. The proper combination of turbulent model and wall treatment is then recommended for the turbulent flow within a bayonet tube. The study focuses on the heat transfer performance at the interface of working fluid and the outer tube wall under different Reynolds numbers. Various geometry parameters are considered in this work and the impact of geometry on the heat transfer performance is investigated. Results indicate that the heat transfer at the bottom of the bayonet tube is enhanced compared with that at the straight part. At low Re (< 8000), the maximum Nu occurs at the stagnation point, while the position of the maximum Nu moves away from the stagnant point as Re exceeds 8000. The results are believed to be helpful for the optimized design of a bayonet tube with fully turbulent flows.

CFD Prediction for Multi-Jet Impingement Heat Transfer

2009 ◽  
Author(s):  
Y. Q. Zu ◽  
Y. Y. Yan ◽  
J. D. Maltson
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Computational Cost ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Reynolds Stress Model ◽  
Large Eddy Simulation Model ◽  
Flow And Heat Transfer ◽  
Shear Stress Transport ◽  
Impingement Heat Transfer

In this paper, the flow and heat transfer characteristics of two lines of staggered or inline round jets impinging on a flat plate are numerically analyzed using the CFD commercial code FLUENT. Firstly, the relative performance of seven versions of turbulence models, including the standard k-ε model, the renormalization group k-ε model, the realizable k-ε model, the standard k-ω model, the Shear-Stress Transport k-ω model, the Reynolds stress model and the Large Eddy Simulation model, for numerically predicting single jet impingement heat transfer is investigated by comparing the numerical results with available benchmark experimental data. As a result, the Shear-Stress Transport k-ω model is recommended as the best compromise between the computational cost and accuracy. Using the Shear-Stress Transport k-ω model, the impingement flow and heat transfer under multi-jets with different jet distributions and attack angles are simulated and studied. The effect of hole distribution and angle of attack, etc. on the heat transfer coefficient of the target plate are examined.

Numerical Simulation of Oblique Air Jet Impingement on a Heated Flat Plate

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Abhishek B. Bhagwat ◽  
Arunkumar Sridharan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flat Plate ◽  
Numerical Study ◽  
Jet Impingement ◽  
Maximum Heat ◽  
Air Jet ◽  
Maximum Heat Transfer ◽  
Vertical Jet

Jet impingement cooling has been studied extensively as this finds applications in the areas of reactor safety, electronic cooling, etc. Here, the convective heat transfer process between the air jet impingement on a uniformly heated inclined flat plate is studied numerically. In this numerical study, 3D simulations are carried out using commercial CFD code to investigate the effect of angle of inclination of plate, Reynolds number, and distance between the nozzle exit and the plate on the heat transfer characteristics. V2F model has been used to model turbulence for various nozzle–plate distance and Reynolds number. It can be concluded that V2F model predicts the Nusselt number variation on the plate satisfactorily. It is observed that point of maximum heat transfer is at the stagnation point in case of vertical jet impinging on a horizontal plate, while it shifts away from the point of impingement for the case of a vertical jet impinging on an inclined flat surface. The shift is toward the “compression side” or the “uphill side” of the air jet. The results are validated with experimental data from the literature. Detailed analysis of local heat transfer coefficients, velocity contours, temperature contours, and Nusselt number variations on the flat plate is presented.

Numerical study on flow and heat transfer characteristics of air-jet cooling system

2018 ◽  
Vol 32 (12) ◽  
pp. 6021-6027 ◽  
Author(s):  
Joo Hyun Moon ◽  
Soyeong Lee ◽  
Jee Min Park ◽  
Jungho Lee ◽  
Daejoong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Jet Cooling ◽  
Flow And Heat Transfer ◽  
Air Jet

scholarly journals Local Heat Transfer Distributions in Confined Multiple Air Jet Impingement

2000 ◽  
Vol 123 (3) ◽  
pp. 165-172 ◽  
Author(s):  
Suresh V. Garimella ◽  
Vincent P. Schroeder
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Air Jets ◽  
Air Jet ◽  
Multiple Jets ◽  
Single Jet ◽  
Radial Outflow ◽  
Target Spacing

Heat transfer from a discrete heat source to multiple, normally impinging, confined air jets was experimentally investigated. The jets issued from short, square-edged orifices with still-developing velocity profiles on to a foil heat source which produced a constant heat flux. The orifice plate and the surface containing the heat source were mounted opposite each other in a parallel-plates arrangement to effect radial outflow of the spent fluid. The local surface temperature was measured in fine increments over the entire heat source. Experiments were conducted for different jet Reynolds numbers (5000<Re<20,000), orifice-to-target spacing 0.5<H/d<4, and multiple-orifice arrangements. The results are compared to those previously obtained for single air jets. A reduction in orifice-to-target spacing was found to increase the heat transfer coefficient in multiple jets, with this effect being stronger at the higher Reynolds numbers. With a nine-jet arrangement, the heat transfer to the central jet was higher than for a corresponding single jet. For a four-jet arrangement, however, each jet was found to have stagnation-region heat transfer coefficients that were comparable to the single-jet values. The effectiveness of single and multiple jets in removing heat from a given heat source is compared at a fixed total flow rate. Predictive correlations are proposed for single and multiple jet impingement heat transfer.

A Numerical Study of a Single Unsteady Laminar Slot Jet in a Confined Structure

2013 ◽  
Author(s):  
Omidreza Ghaffari ◽  
M. Baris Dogruoz ◽  
Mehmet Arik
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Numerical Study ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Air Cooling ◽  
Complex Flow ◽  
Potential Core ◽  
Flow And Heat Transfer ◽  
Surface Profiles

With the inherit advantages of air cooling, jet impingement can produce a factor of two or higher heat transfer than conventional fan flow over bodies. Therefore, impinging jets can solve a number of electronics thermal issues. Those jets produce complex flow and thermal structures leading to non-uniform and non-monotonic profiles on target surfaces. A numerical study is performed to investigate the flow and heat transfer characteristics of an unsteady laminar impinging jet emanated from a single high-aspect ratio rectangular (slot) nozzle in a confined arrangement. The spacing between the target plate and the nozzle is such that the jet would still be in its potential core length as it was in a free axial jet. Following the initial transients, flow and heat transfer parameters still vary considerably in time that the instantaneous and time-averaged values of surface profiles are not identical. Instantaneous surface pressure distributions exhibit that the stagnation point translates periodically around the initial jet-symmetry line and the surface profiles demonstrate off-center (non-stagnation point) peaks.

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