Experimental and Theoretical Studies of Mist Jet Impingement Cooling

1996 ◽  
Vol 118 (2) ◽  
pp. 343-349 ◽  
Author(s):  
K. M. Graham ◽  
S. Ramadhyani
Keyword(s):  
Experimental Data ◽  
Jet Impingement ◽  
Target Surface ◽  
Heat Fluxes ◽  
Heat Sources ◽  
Impingement Cooling ◽  
Jet Cooling ◽  
Air Jet ◽  
Model Predictions ◽  
Experimental And Theoretical Studies

Experimental data and analytical predictions for air/liquid mist jet cooling of small heat sources are presented. The mist jet was created using a coaxial jet atomizer, with a liquid jet of diameter 190 μm located on the axis of an annular air jet of diameter 2 mm. The impingement surface was a square of side 6.35 mm. Experimental data were obtained with mists of both methanol and water. Surface-averaged heat fluxes as high as 60 W/cm2 could be dissipated with the methanol/air mist while maintaining the target surface below 70°C. With the water/air mist, a heat flux of 60 W/cm2 could be dissipated with the target surface at 80°C. Major trends in the data and model predictions have been explained in terms of the underlying hydrodynamic and heat transfer phenomena.

scholarly journals Cold Zone Exploration Using Position of Maximum Nusselt Number for Inclined Air Jet Cooling

2017 ◽  
Vol 64 (4) ◽  
pp. 533-549 ◽  
Author(s):  
Sunil B. Ingole ◽  
K. K. Sundaram
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Air Cooling ◽  
Cold Zone ◽  
Jet Cooling ◽  
Air Jet ◽  
Cold Spots

Abstract Inclined jet air cooling can be effectively used for cooling of electronics or other such applications. The non-confined air jet is impinged and experimentally investigated on the hot target surface to be cooled, which is placed horizontally. Analysis and evaluations are made by introduction of a jet on the leading edge and investigated for downhill side cooling to identify cold spots. The jet Reynolds number in the range of 2000 ≤ Re ≤ 20 000 is examined with a circular jet for inclination (Θ) of 15 < Θ < 75 degree. Also, the consequence of a jet to target distance (H) is explored in the range 0:5 ≤ H/D ≤ 6.8. For 45 degree jet impingement, the maximum Nusselt number is widely spread. Location of maximum Nusselt number is studied, which indicates cold spots identification. At a higher angle ratio, the angle is the dominating parameter compared to the Reynolds Number. Whereas at a lower angle ratio, the inclined jet with a higher Reynolds number is giving the cooling point away from leading edge. It is observed that for a particular angle of incident location of maximum Nusselt Number, measured from leading edge of target, is ahead than that of stagnation point in stated conditions.

The Consequence of Target Surface Curvature in the Jet Impingement Cooling

2015 ◽  
Vol 766-767 ◽  
pp. 1148-1152
Author(s):  
M. Karthigairajan ◽  
S. Mohanamurugan ◽  
K. Umanath
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convex Surface ◽  
Heated Surface ◽  
Jet Impingement ◽  
Target Surface ◽  
Uniform Heat Flux ◽  
Impingement Cooling ◽  
Air Jet ◽  
Increase With Increase

An experiment sturdy has been carried out for jet impingement cooling on the spherically convex surface is the development of mechanism. The effect of curvature, Space between jet exit and target surface, and Reynolds number on heat transfer is investigated for around air jet on hemispherical surface. The flow at the jet exit has fully developed velocity profile. A uniform heat flux boundary is created on the heated surface. The experiments are performed for 5000<Re<25000, 2<L/d<10, and jet diameters ranging from 1.3, 2.1, 3.4, 4.0 and 5.2 cm. In the mean time effect of curvature on local heat transfer is negligible at the wall jet region corresponding to r/d>0.5. From the experimental results the variation of the D/d ratio with local Nusselt number (Nust) for various Reynolds numbers and various L/d ratios are plotted. The results show that Nust increase with increase in curvature and the effect of the curvature will high at high Reynolds number. i.e. Nust at Re=25000 is 25% higher than at Re= 5000 This may be attributed to an increase in curvature increases acceleration, & size of three dimensional counter rotating vortices at stagnation point and the increment of Reynolds number increases the jet momentum, and also enhances the vortices creation. Nust is peaking in the L/d ratio of 6 because of high turbulence intensity as this distance.

scholarly journals Air Jet Impingement Cooling of Electronic Devices Using Additively Manufactured Nozzles

2020 ◽  
Vol 10 (2) ◽  
pp. 220-229 ◽  
Author(s):  
Beomjin Kwon ◽  
Thomas Foulkes ◽  
Tianyu Yang ◽  
Nenad Miljkovic ◽  
William P. King
Keyword(s):  
Electronic Devices ◽  
Jet Impingement ◽  
Impingement Cooling ◽  
Air Jet

Microelectromechanical System-Based Evaporative Thermal Management of High Heat Flux Electronics

2005 ◽  
Vol 127 (1) ◽  
pp. 66-75 ◽  
Author(s):  
Cristina H. Amon ◽  
S.-C. Yao ◽  
C.-F. Wu ◽  
C.-C. Hsieh
Keyword(s):  
Microelectromechanical Systems ◽  
Surface Texturing ◽  
Jet Impingement ◽  
Heat Fluxes ◽  
Future Research ◽  
Dielectric Fluid ◽  
Practical Implementation ◽  
High Heat Flux ◽  
Droplet Impingement ◽  
Impingement Cooling

This paper describes the development of embedded droplet impingement for integrated cooling of electronics (EDIFICE), which seeks to develop an integrated droplet impingement cooling device for removing chip heat fluxes over 100W/cm2, employing latent heat of vaporization of dielectric fluids. Micromanufacturing and microelectromechanical systems are used as enabling technologies for developing innovative cooling schemes. Microspray nozzles are fabricated to produce 50–100 μm droplets coupled with surface texturing on the backside of the chip to promote droplet spreading and effective evaporation. This paper examines jet impingement cooling of EDIFICE with a dielectric coolant and the influence of fluid properties, microspray characteristics, and surface evaporation. The development of micronozzles and microstructured surface texturing is discussed. Results of a prototype testing of swiss-roll swirl nozzles with dielectric fluid HFE-7200 on a notebook PC are presented. This paper also outlines the challenges to practical implementation and future research needs.

Electronic Cooling Using Synthetic Jets

2005 ◽  
Author(s):  
Anna A. Pavlova ◽  
Michael Amitay
Keyword(s):  
Reynolds Number ◽  
Heated Surface ◽  
Low Frequency ◽  
Heat Removal ◽  
Jet Impingement ◽  
Constant Heat Flux ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Impingement Cooling ◽  
Jet Cooling

Efficiency of synthetic jet impingement cooling and the mechanisms of heat removal from a constant heat flux surface were investigated experimentally. The effects of jet’s formation frequency and Reynolds number at different nozzle-to-surface distances were investigated and compared to steady jet cooling. It was found that synthetic jets are up to three times more effective than steady jets at the same Reynolds number. For smaller distances, high formation frequency (f = 1200 Hz) synthetic jets remove heat better than low frequency (f = 420 Hz) jets, whereas low frequency jets are more effective at larger distances, with an overlapping region. Using PIV, it was shown that at small distances between the synthetic jet and the heated surface, the higher formation frequency jet is associated with accumulation of vortices before they impinge on the surface. For the lower frequency jet, the wavelength between coherent structures is so large that vortex rings impinge on the surface separately.

Experimental Investigation of Single-Phase Micro Jets Impingement Cooling for Electronic Applications

2003 ◽  
Author(s):  
Matteo Fabbri ◽  
Shanjuan Jiang ◽  
Vijay K. Dhir
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Free Surface ◽  
Single Phase ◽  
Impinging Jets ◽  
Heat Fluxes ◽  
Number Range ◽  
Impingement Cooling ◽  
Circular Arrays

Impinging jets for cooling of electronic equipment have been used by many researchers. Only few studies using arrays composed of a small number of jets are available in the literature. When very small jet diameters are used, the jet Reynolds number becomes quite small and no data are available for Reynolds number values below 500. In this work attention has been focused on circular arrays of free surface micro jets. Experiments were conducted by employing three jet pitches, 1, 2 and 3 mm and four jet diameters 50, 100, 150 and 250 μm and two different fluids, DI water and FC 40. The jet Reynolds number range was varied between 90 and 2000 while the Prandtl number varied from 6 to 84. Heat fluxes as high as 250 W/cm2 could be removed when water was utilized. Experimental data have been correlated within ±20%.

Heat Transfer Characteristic Analysis of Confined Impinging Jet Cooling System with Micro-Scale Round Nozzles

2010 ◽  
Vol 171-172 ◽  
pp. 799-803
Author(s):  
Chang Hong Wang ◽  
Ying Chen ◽  
Juan Tu
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Transfer Characteristic ◽  
Characteristic Analysis ◽  
Chip Cooling ◽  
Jet Cooling ◽  
Air Jet ◽  
Nozzle Type

In order to investigate the heat transfer of confined impinging jet with tiny size round nozzle, a bakelite laminate was used as the heat transfer surface of simulated chip. The thermocouples were mounted symmetrically along the diagonal of the laminate to measure the temperature distribution of the surface. The parameters such as Reynolds number (Re) and ratio of height-to-diameter were changed to investigate the radial distribution of Nu and the characteristics of heat transfer in stagnant section. The results show that hear transfer coefficient at stagnation point is maximal. It is decreased with the increases of the radial jet distance, but increased with Re and impinging height. Moreover, the effect of single-nozzle type is stronger than that of multi-nozzle type in the cases of same air flow. These studies will give a way for the application of air jet impingement in the electronics chip cooling.

scholarly journals Conjugate Effect on the Thermal Characteristics of Air Impinging Jet

CFD Letters ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 25-35
Author(s):  
Ghassan Nasif ◽  
Yasser El-Okda
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Convective Heat ◽  
Thermal Characteristics ◽  
Heat Fluxes ◽  
Conductive Heat ◽  
Stagnation Region ◽  
Jet Cooling ◽  
Air Jet ◽  
Finite Volume Approach

A computational fluid dynamics (CFD) investigation to determine the conjugate heat transfer (CHT) effect on the stagnation and local thermal characteristics due to an impinging process has been carried out in this study using STAR-CCM+ - Siemens PLM commercial code. The transient Navier-Stokes’s equations are numerically solved using a finite volume approach with k-ω SST eddy viscosity as the turbulence model. A fully developed circular air jet with different Reynolds numbers, impinging vertically onto a heated flat disc with different metals, thicknesses, and boundary heat fluxes are employed in the current study to examine the thermal characteristics and provide an enhanced picture for the convection mechanism that used in jet cooling technology. It is found that the thermal characteristics are influenced by the thermal conductivity and thickness of the target upon using air as a cooling jet. The CHT process enhances the local convective heat transfer at the fluid-solid interface due to the variation in transverse and axial conductive heat transfer inside the metal up to a certain redial extent from the stagnation region compared to the process with no CHT. The extent of the radial enhancement depends on the thermal conductivity of the metal. For a given thermal conductivity, the CHT process acts to increase the temperature and convective heat flux of the stagnation region as the metal thickness increases.

Experimental and Numerical Study of Jet Impingement Cooling for Improved Gas Turbine Blade Internal Cooling With In-Line and Staggered Nozzle Arrays

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Abdel Rahman Salem ◽  
Farah Nazifa Nourin ◽  
Mohammed Abousabae ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Numerical Study ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Target Surface ◽  
Internal Cooling ◽  
Impingement Cooling ◽  
Gas Turbine Blades

Abstract Internal cooling of gas turbine blades is performed with the combination of impingement cooling and serpentine channels. Besides gas turbine blades, the other turbine components such as turbine guide vanes, rotor disks, and combustor wall can be cooled using jet impingement cooling. This study is focused on jet impingement cooling, in order to optimize the coolant flow, and provide the maximum amount of cooling using the minimum amount of coolant. The study compares between different nozzle configurations (in-line and staggered), two different Reynold's numbers (1500 and 2000), and different stand-off distances (Z/D) both experimentally and numerically. The Z/D considered are 3, 5, and 8. In jet impingement cooling, the jet of fluid strikes perpendicular to the target surface to be cooled with high velocity to dissipate the heat. The target surface is heated up by a direct current (DC) power source. The experimental results are obtained by means of thermal image processing of the captured infra-red (IR) thermal images of the target surface. Computational fluid dynamics (CFD) analysis were employed to predict the complex heat transfer and flow phenomena, primarily the line-averaged and area-averaged Nusselt number and the cross-flow effects. In the current investigation, the flow is confined along with the nozzle plate and two parallel surfaces forming a bi-directional channel (bi-directional exit). The results show a comparison between heat transfer enhancement with in-line and staggered nozzle arrays. It is observed that the peaks of the line-averaged Nusselt number (Nu) become less as the stand-off distance (Z/D) increases. It is also observed that the fluctuations in the stagnation heat transfer are caused by the impingement of the primary vortices originating from the jet nozzle exit.

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