Predictions of Thermal and Hydrodynamic Characteristics of a Single Circular Micro-Jet Impinging on a Flat Plate

2008 ◽  
Author(s):  
Marcel Le´on De Paz ◽  
B. A. Jubran
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Reference Model ◽  
Preliminary Investigation ◽  
Jet Impingement ◽  
Hydrodynamic Characteristics ◽  
Transfer Rates ◽  
Impingement Cooling ◽  
3 Dimensional

Jet impingement cooling remains one of the key methods in various high-end cooling applications as it can induce higher heat transfer rates. The objective of this preliminary investigation is to shed some light on micro-impingement cooling and assess the accuracy for a future 3-dimensional turbine blade model. For the purpose of this study, several micro-jet impingement cases are modeled in Gambit and iterated with Fluent. The reference model consists of a single 500μm cylindrical nozzle impinging on a constant temperature flat plate. Conducive results were found on the effects of turbulence model, Reynolds number, and H/D ratio for the Nusselt distribution on the flat plate. The Reynolds numbers iterated were: 2000, 3000, 4000, 5000, and 6000. The different H/D ratios modeled were: 6, 5, 4, 3, 2, 1. In general, it was observed that a higher Reynolds number increased the heat transfer on the plate, but the jet to target spacing had no significant impact on it. All results were validated via comparison with several published experimental data, the deviation margins indicated a good agreement.

Impingement Cooling by Multiple Asymmetric Orifice Jets

2021 ◽  
Author(s):  
Chunyu Zhang ◽  
Yanyan Liu ◽  
Taahir Bhaiyat ◽  
Sjouke Schekman ◽  
Tian Jian Lu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Thermal Characteristics ◽  
Jet Impingement ◽  
Diameter Ratio ◽  
Impingement Cooling ◽  
Blunt Edge ◽  
Surrounding Fluid ◽  
Target Spacing

Abstract This study presents impingement cooling from a flat plate by multiple asymmetric jets. Such jets are discharged through blunt-edge inline orifice holes with a thickness-to-diameter ratio of t/Dj = 0.5 and a jet-to-jet spacing of T/Dj = 4.0, at the Reynolds number of 20,000. Firstly, fluidic features are established both in free exit and with impingement, at varying short target spacing (e.g., H/Dj = 4.0). Secondly, thermal characteristics of the jet impingement are elucidated. Results demonstrate that, due to a skewed incidence of the coolant stream upstream of concave orifice holes, the resulting multiple orifice jets are asymmetric and skewed relative to the orifice axis. These results mimic multiple fluidically inclined jets. However, asymmetric entrainment that takes place causes faster mixing with the surrounding fluid at rest as well as faster decay of momentum. This shows more effective cooling from a flat plate for the relatively short H/Dj range than conventional symmetric orifice and nozzle jets.

Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement Cooling

2011 ◽  
Vol 148-149 ◽  
pp. 680-683
Author(s):  
Run Peng Sun ◽  
Wei Bing Zhu ◽  
Hong Chen ◽  
Chang Jiang Chen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Cross Flow ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Transfer Characteristic ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Three-dimensional numerical study is conducted to investigate the heat transfer characteristics for the flow impingement cooling in the narrow passage based on cooling technology of turbine blade.The effects of the jet Reynolds number, impingement distance and initial cross-flow on heat transfer characteristic are investigated.Results show that when other parameters remain unchanged local heat transfer coefficient increases with increase of jet Reynolds number；overall heat transfer effect is reduced by initial cross-flow；there is an optimal distance to the best effect of heat transfer.

Effects of Nanoparticle Shape on Slot-Jet Impingement Cooling of a Corrugated Surface With Nanofluids

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Jet Impingement ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Corrugated Surface ◽  
Nanoparticle Shapes

Numerical study of jet impingement cooling of a corrugated surface with water–SiO2 nanofluid of different nanoparticle shapes was performed. The bottom wall is corrugated and kept at constant surface temperature, while the jet emerges from a rectangular slot with cold uniform temperature. The finite volume method is utilized to solve the governing equations. The effects of Reynolds number (between 100 and 500), corrugation amplitude (between 0 and 0.3), corrugation frequency (between 0 and 20), nanoparticle volume fraction (between 0 and 0.04), and nanoparticle shapes (spherical, blade, brick, and cylindrical) on the fluid flow and heat transfer characteristics were studied. Stagnation point and average Nusselt number enhance with Reynolds number and solid particle volume fraction for both flat and corrugated surface configurations. An optimal value for the corrugation amplitude and frequency was found to maximize the average heat transfer at the highest value of Reynolds number. Among various nanoparticle shapes, cylindrical ones perform the best heat transfer characteristics in terms of stagnation and average Nusselt number values. At the highest solid volume concentration of the nanoparticles, heat transfer values are higher for a corrugated surface when compared to a flat surface case.

Effectiveness of Jet Impingement Cooling System on Convex Surface

2016 ◽  
Vol 819 ◽  
pp. 74-77
Author(s):  
Mohamad Nor Musa ◽  
Mohamad Faizal Fauzi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Convex Surface ◽  
Cooling System ◽  
Jet Impingement ◽  
Impingement Cooling ◽  
Reynolds Number Increase ◽  
Number Increase

Jet impingement is one of cooling method used in order to achieve high heat transfer coefficient and widely used in industry applications such as drying of textile and film, glass and plastic sheets, cooling of electronic equipment, and heat treatment of metals. In this research, it focused on the effectiveness of the jet impingement cooling system on the convex surface based on mass blowing rate and nozzle exit to surface parameters. The scope of experiment research encompasses are convex surface made of aluminum alloy and diameter 12.5cm. For mass blowing rate parameters, it use ʋjet = 1.98m/s, 3.03m/s, 4.97m/s and 6.00m/s which has Reynolds number range from 643 until 1946. Nozzle exit to surface distance,s/d = 4.0, 8.0 and 12.0. In this experiment model, a major components that involved are a compressor, nozzle, convex surface model, K thermocouple and heater. For the result of the experiment, it is based on the data obtain through a heat transfer coefficient and Nusselt number which the plotted graph focus on the space spacing and Reynolds number parameters. For the graph Nusselt number versus s/d at stagnation point c/d=0, it shown that when the Reynolds number increase, the Nusselt number also increase. In term of effectiveness, the s/d=12.0 has a good effectiveness jet impingement cooling system. For the graph of Nusselt number versus Reynolds at stagnation point, c/d=0, as Reynolds number increase, the Nusselt number increase too. From this experiment the better cooling effect is at Reynolds number, Re=1946. Thus, it can conclude that, effectiveness for jet impingement cooling system on the convex surface occurs at the highest Reynolds number.

scholarly journals Micro scale jet impingement cooling and its efficacy on turbine vanes : a numerical study

2021 ◽  
Author(s):  
Santhiya Jayaraman
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Leading Edge ◽  
Jet Impingement ◽  
3D Analysis ◽  
Transfer Rates ◽  
Impingement Cooling ◽  
Micro Scale ◽  
Turbine Vane ◽  
Nozzle Configuration

A numerical analysis of effectiveness of micro-jet impingement cooling on leading edge of a turbine vane is presented. An axisymmetric single round jet was assessed for its ability and consistency as a preliminary study including the investigation of parameters influencing the heat transfer distribution. The analysis revealed that an increase in Nusselt number was attributed to increase in Reynolds number, decrease in jet diameter and H/D < 3. Significant improvement in heat transfer was observed for tapering nozzle configuration. The study was then further expanded to 3D analysis of leading edge cooling of turbine vane. Effect of nozzle diameter to micro-scale was studied, which showed 65% enhancement in the heat transfer rates.

scholarly journals Conjugate Heat Transfer Analysis of Flat Plate Subjected to Impingement and Film Cooling

2021 ◽  
Vol 9 (9) ◽  
pp. 1667-1678
Author(s):  
Devaraj K
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flat Plate ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

Abstract: The present computational study involves a flat plate subjected to combined effect of jet impingement and film cooling. A conjugate heat transfer model in conjunction with k-ω SST turbulence model is employed to study the turbulence effects. The effect of Reynolds number varying from 389 to 2140 on static temperature, Nusselt number and film cooling effectiveness has be discussed for the blowing ratios of 0.6, 0.8, 1.0. The variation in the size of vortices formed on the impinging surface with Reynolds number is studied. It has been observed that the local Nusselt number shows a rising trend with the increase in Reynolds number, while the static temperatures follow the downfall in its values. As a result, an enhancement in the effectiveness is observed, which is credited to the capabilities of combined impingement and film cooling. At Reynolds number of 972, the coolant jet is found to be attached to the surface, for this condition the heat transfer phenomena for blowing ratios of 0.6, 0.8, 1.0, 1.2, 1.6, 2.0, 2.4, 2.6 are studied to understand the flow distribution on the plate surface. Keywords: Jet impingement, film cooling, effectiveness, conjugate heat transfer

scholarly journals Micro scale jet impingement cooling and its efficacy on turbine vanes : a numerical study

2021 ◽  
Author(s):  
Santhiya Jayaraman
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Leading Edge ◽  
Jet Impingement ◽  
3D Analysis ◽  
Transfer Rates ◽  
Impingement Cooling ◽  
Micro Scale ◽  
Turbine Vane ◽  
Nozzle Configuration

A numerical analysis of effectiveness of micro-jet impingement cooling on leading edge of a turbine vane is presented. An axisymmetric single round jet was assessed for its ability and consistency as a preliminary study including the investigation of parameters influencing the heat transfer distribution. The analysis revealed that an increase in Nusselt number was attributed to increase in Reynolds number, decrease in jet diameter and H/D < 3. Significant improvement in heat transfer was observed for tapering nozzle configuration. The study was then further expanded to 3D analysis of leading edge cooling of turbine vane. Effect of nozzle diameter to micro-scale was studied, which showed 65% enhancement in the heat transfer rates.

Experimental Study of Air Slot Jet Impingement Cooling From Cylinder Placed on a Flat Plate

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
Ketan Atulkumar Ganatra ◽  
Dushyant Singh
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Nusselt Number ◽  
Flat Plate ◽  
Local Nusselt Number ◽  
Jet Impingement ◽  
Maximum Error ◽  
Constant Heat Flux ◽  
Impingement Cooling ◽  
Heated Cylinder

Abstract The experimental study for air slot jet impingement cooling from the heated cylinder is carried out. The heated cylinder is placed on a flat plate. The flat plate has an effective dimension as plate length (P) from heat transfer point of view. The heating of the cylindrical surface is done by providing a constant heat flux. The various parameters which affect the heat transfer from the cylinder are ReD, h/S, S/D, and P/D. The range of the parameters considered are ReD = 10,000–25,000, h/S = 4–12, S/D = 0.072–0.108, and P/D = 0–2. The effect of various parameters on heat transfer distribution (stagnation and local Nusselt number) from the cylinder is investigated. The local Nusselt number has a maximum value at θ = 0 deg and then it decreases upto θ = 180 deg. This trend is observed for all the parametric variations. The stagnation Nusselt number (Nustag) and local Nusselt number increases with the change of parameters as increase in ReD and S/D and decrease in h/S. However, Nustag remains independent with the change in P/D. The correlation for stagnation and mean Nusselt number is developed using regression analysis as a function of ReD, h/S, S/D, and P/D. The maximum error associated with the correlated value of Nustag and Num as compared with the experimental data is observed as ±13% and ±25%.

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 Jet Impingement

2011 ◽  
Author(s):  
Xinjun Wang ◽  
Rui Liu ◽  
Xiaowei Bai ◽  
Jinling Yao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Target Surface ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

A mathematical model used for studying jet impingement cooling characteristics is established, and the rationality of the calculation model and method is confirmed by the experimental data. The CFX software is used to numerically simulate the jet impingement cooling characteristics on a gas turbine blade. The effects of various parameters, such as the arrays of impinging nozzles, the jet Reynolds number, the jet-to-jet distance, the ratio of nozzle-to-surface spacing to jet diameter H/d, and the radius of curvature of the target surface, on the flow and heat transfer characteristics of a impingement cooling process are studied. The results indicate that the impingement jets can make complex vortex in the cooling channel, the flow boundary layer is extremely thin and highly turbulent. Underneath each impingement nozzle, there will appear a low temperature area and a peak of Nusselt number on the impingement target surface, the distribution of temperature and Nusselt number on the target surface are associated with arrangement of impingement nozzles. The average Nusselt number of the in-line arrangement nozzles is higher than that of the staggered arrangement ones. With the increasing of jet Reynolds number, the velocity impinging on the target surface and Nusselt number increase. However, heat transfer of impingement cooling on target surface is not sensitive to the jet nozzles distance; the velocity impinging on the target surface and Nusselt number decrease with the increasing of the H/d value. For the curved target surface cases, the average Nusselt number of the target surface and the effect of heat transfer decreased with the increasing of curvature radius R.

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