Submerged Jet Impingement Boiling on a Polished Silicon Surface

2011 ◽  
Author(s):  
Preeti Mani ◽  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Silicon Surface ◽  
High Speed ◽  
Jet Impingement ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Submerged Jet ◽  
Jet Impingement Boiling

Submerged jet impingement boiling has the potential to enhance pool boiling heat transfer rates. In most practical situations, the surface could consist of multiple heat sources that dissipate heat at different rates resulting in a surface heat flux that is non-uniform. This paper discusses the effect of submerged jet impingement on the wall temperature characteristics and heat transfer for a non-uniform heat flux. A mini-jet is caused to impinge on a polished silicon surface from a nozzle having an inner diameter of 1.16 mm. A 25.4 mm diameter thin-film circular serpentine heater, deposited on the bottom of the silicon wafer, is used to heat the surface. Deionized degassed water is used as the working fluid and the jet and pool are subcooled by 20°C. Voltage drop between sensors leads drawn from the serpentine heater are used to identify boiling events. Heater surface temperatures are determined using infrared thermography. High-speed movies of the boiling front are recorded and used to interpret the surface temperature contours. Local heat transfer coefficients indicate significant enhancement upto radial locations of 2.6 jet diameters for a Reynolds number of 2580 and upto 6 jet diameters for a Reynolds number of 5161.

Nonuniform Temperature Distribution in Electronic Devices Cooled by Flow in Parallel Microchannels

2000 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Distribution ◽  
High Speed ◽  
Flow Boiling ◽  
Convection Heat Transfer ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Two Phase ◽  
Parallel Microchannels

Abstract We fabricated a novel thermal microsystems (simulating a computer chip) consisting of a heater, microchannels, inlet and outlet plena and we studied the effect of the geometry on the flow and heat transfer. The vapor - water two-phase flow patterns were observed in the parallel microchannels through a microscope and high-speed video camera. It was observed that hydraulic instabilities occur. Existence of a periodic annular flow was also observed, which consist of a symmetrically distributed liquid ring surrounding the vapor core. Along the microchannel axis, the periodic dry zone appears and develops. The thermal visualization and temperature measurements of the heated device were carried out using infrared thermography. As long as the flow was single phase liquid, the forced convection heat transfer resulted in a moderate irregularity on the heated chip. These temperature differences do not cause damage to the device. The steady-state heat transfer for different types of microchannels has been studied also at the range of heat flux where phase change of the working fluid from liquid to vapor took place. Under conditions of flow boiling in microchannels, a significant enhancement of heat transfer was established. In the case of uniform heat flux the hydraulic instabilities lead to irregularity of temperature distribution on the heated chip. In the case of nonuniform heat flux the irregularity increased drastically.

Submerged Jet Impingement Boiling of Water Under Subatmospheric Conditions

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Jet Impingement ◽  
Nucleate Boiling ◽  
Pressure Surface ◽  
Wall Superheat ◽  
Jet Impingement Boiling

An experimental study of jet impingement boiling is presented for water under saturated and subcooled conditions. Unique to this study is the documentation of boiling curves of a submerged water jet under subatmospheric conditions. Data are reported at a fixed nondimensional nozzle-to-surface distance of H/dj = 6 and for a fixed surface-to-nozzle diameter ratio, dsurf/dj, of 23.8. Saturated jet impingement experiments are performed at three subatmospheric pool pressures of 0.176 bar, 0.276 bar, and 0.478 bar with corresponding saturation temperatures of 57.3 °C, 67.2 °C, and 80.2 °C. At each pressure, jet impingement boiling at varying Reynolds numbers are characterized and compared with pool boiling heat transfer. The effect of surface roughness and fluid subcooling is studied at the lowest pressure of 0.176 bar. Boiling curves indicate a strong dependence of heat flux on jet Reynolds number in the partially developed nucleate boiling region but only a weak dependence in the fully developed nucleate boiling region. At a fixed wall superheat, fluid subcooling is found to shift the boiling curve to the left thereby enhancing heat transfer performance. Critical heat flux is found to increase with increases in pressure, surface roughness, and Reynolds number.

Numerical Investigation of a Confined Laminar Jet Impingement Cooling of Heat Sources Using Nanofluids

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Orkodip Mookherjee ◽  
Shantanu Pramanik ◽  
Uttam Kumar Kar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Base Fluid ◽  
Strong Dependence ◽  
Jet Impingement ◽  
Effective Density ◽  
Eckert Number ◽  
Maximum Temperature ◽  
Pumping Power

Abstract The thermal and fluid dynamic behavior of a confined two-dimensional steady laminar nanofluid jet impinging on a horizontal plate embedded with five discrete heating elements subjected to a constant surface heat flux has been studied for a range of Reynolds number (Re) from 100 to 400 with Prandtl number, Pr = 6.96, of the base fluid. Variation of inlet Reynolds number produces a significant change of the flow and heat transfer characteristics in the domain. Increasing the nanoparticle concentration (ϕ) from 0% to 4% exhibits discernible change in equivalent Re and Pr caused by the modification of dynamic viscosity, effective density, thermal conductivity, and specific heat of the base fluid. Considerable improvement in heat transfer from the heaters is observed as the maximum temperature of the impingement wall is diminished from 0.95 to 0.55 by increasing Re from 100 to 400; however, the result of increasing ϕ on cooling of the heaters is less appreciable. Self-similar behavior has been depicted by cross-stream variation of temperature and streamwise heat flux in the developed region along the impingement wall up to Re = 300 for ϕ=0% to 4%. But the spread of the respective quantities shows strong dependence on ϕ at Re = 300 with sudden attenuation in magnitude in the developed region of flow. Substantial influence of Re is evident on Eckert number and pumping power. Eckert number decreases, whereas pumping power increases with an increase in Re, and the respective variations exhibit correspondence with power fit correlations.

scholarly journals Experimental Investigation of The Influence of Mechanical Forced Vibrations and Heat Flux on Coefficient of Heat Transfer

2018 ◽  
Vol 6 (3) ◽  
pp. 124-129
Author(s):  
Adil Bash ◽  
Aadel Alkumait ◽  
Hamza Yaseen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Forced Vibration ◽  
Vibration Amplitude ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
New Correlation

The aim of this paper to verify the influence of vertical forced vibration on the coefficient of heat transfer of the laminar internal flow in a spiral fluted tube. With adopted the water as a working fluid, and flowing Reynolds numbers at the entrance between 228 and 1923, the tube heated under constant heat flux levels ranging from 618-3775 W/m2. The frequencies of vibration ranging from 13 to 30 Hz, and the amplitudes of vibration from 0.001 to 0.002 mm. The results appeared that the coefficient of heat transfer significantly affected by mechanical forced vibration in a flowing of the heated tube. When the vibration amplitude increases, the Nusselt number Significantly increases, with the maximum increases of 8.4% at the amplitude of vibration 0.0022 mm and the frequency 13 Hz. Generally, the coefficient of heat transfer increases with increasing Reynolds number and heat flux. At last, by using the parameters of vibration amplitude, frequency, heat flux and Reynolds number, a new correlation has been derived depends on experimental data.

Critical Heat Flux During Submerged Jet Impingement Boiling of Saturated Water at Sub-Atmospheric Conditions

2011 ◽  
Author(s):  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Jet Impingement ◽  
Atmospheric Conditions ◽  
Predictive Tool ◽  
Submerged Jet ◽  
Fluid Saturation ◽  
Saturated Water ◽  
Jet Impingement Boiling

Experimental data for critical heat flux (CHF) during submerged jet impingement boiling of saturated water at sub-atmospheric conditions is presented. Experiments are performed at three sub-atmospheric pressures of 0.176 bar, 0.276 bar, and 0.477 bar with corresponding fluid saturation temperatures of about 57.3 °C, 67.2 °C, and 80.2 °C. Jet exit Reynolds numbers ranging from 0 to 14,000 are considered for two different heater surface finishes at a fixed nozzle to surface spacing of six nozzle diameters. CHF correlations from literature on jet impingement boiling are compared against the experimental data and found to poorly predict CHF under the conditions considered. A CHF correlation that captures the entire experimental data set within an average error of ±3 percent and a maximum error of ±13 percent is developed to serve as a predictive tool for the range of conditions examined.

Impinging Jet Cooling Optimization for Obtaining Uniform Heat Flux

2010 ◽  
Author(s):  
Farshad Kowsary ◽  
Hamed Gholamian ◽  
Mehran Rajaeeian Hoonejani
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Transfer Problem ◽  
Jet Impingement ◽  
Separation Distance ◽  
Uniform Heat Flux ◽  
Target Plate ◽  
Steady State Condition ◽  
Uniform Heat ◽  
Impingement Heat Transfer

In this study obtaining a uniform heat flux over a target surface was investigated by means of using characteristics of jet impingement heat transfer. Conjugate Gradients Method (CGM) was utilized to minimize the objective function defined on the basis of the squared differences between the target heat flux and the calculated ones. Design variables were taken to be jets’ Reynolds numbers, separation distance between the exit plane of the jets and the target plate, as well as inter-jet spacing. Air single phase jets were used in this study. The problem was solved for the cases of 4 and 6 jets. Temperature difference between the jet exit and the target plate is 100°C, and a steady state condition was assumed. The Finite Volume Method and an unstructured mesh were used for direct solution of the jet impingement heat transfer problem for a laminar jets impingement to a flat plate with constant temperature.

scholarly journals Improvement of thermal homogenization using multiple swirling jets

2012 ◽  
Vol 16 (1) ◽  
pp. 239-250 ◽  
Author(s):  
Mohamed Braikia ◽  
Larbi Loukarfi ◽  
Ali Khelil ◽  
Hassan Naji
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Flow Rate ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Swirling Jets ◽  
Counter Rotation ◽  
The One

The aim of this study is to examine different blowing configurations of multiple swirling jets for use it in terminal units of ventilation applications. The influence of several parameters such as the inclined vanes of diffuser and the sense of rotation of the single or multiple swirling jets, their number and their arrangement on the flow resulting dynamically and thermally is experimentally investigated. Flow rate was adjusted at Reynolds numbers, Re0, ranging from 104 to 30.103. The current study is carried out under uniform heat flux condition for each diffuser at Reynolds number of 30.103, the air being the working fluid. Experiences concerning the fusion of several jets show that the resulting jet is clearly more homogenized under swirling influence. The findings of this study show that the gap between the jets and their sense of rotation relative to the central jet, affects the quality of the homogenization of ambiance. Among the studied different configuration, the one which consists of a swirling central jet controlling the behavior of six swirling jets in counter-rotation is shown to be the most effective in terms of thermal destratification.

Thermal and Flow Visualization of Submerged Jet Impingement Boiling With FC-72

2012 ◽  
Author(s):  
Preeti Mani ◽  
Vinod Narayanan
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Radial Temperature ◽  
Submerged Jet ◽  
Dielectric Fluids ◽  
Wall Superheat ◽  
Chemical Inertness ◽  
Jet Impingement Boiling

Dielectric fluids like FC-72 have been popularly used as electronic coolants owing to their chemical inertness and low saturation temperatures at atmospheric pressure. This work visualizes the heat transfer characteristics of FC-72 during submerged jet impingement boiling on a silicon surface heated by means of a thin film serpentine heater. Infrared thermography is used to obtain quantitative thermal maps of the boiling process from beneath the surface. Simultaneous high-speed visualization is used to record the corresponding bubble dynamics on the top surface. Experiments for two jet Reynolds numbers are compared with pool boiling under saturated conditions at a fixed surface to nozzle diameter ratio. Area-averaged temperatures evaluated from the thermal maps are used to describe the boiling trends for increasing and decreasing heat flux. Wall superheat required for phase-change varies randomly with increasing jet Reynolds numbers. Incipience overshoot as high as ∼21°C is observed and visually documented for the lower jet flow rate. Radial temperature profiles along the surface indicate that locally overshoots may vary significantly (∼8–21°C) for conditions with extremely high incipient superheats.

A Correlation for Critical Heat Flux in Submerged Jet Impingement

2012 ◽  
Author(s):  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Jet Impingement ◽  
Maximum Error ◽  
Nozzle Diameter ◽  
Average Error ◽  
Submerged Jet ◽  
System Pressure ◽  
Wide Range ◽  
Jet Impingement Boiling

Data from an extensive experimental study of submerged jet impingement boiling performed with water at sub-atmospheric pressures and with FC-72 at atmospheric pressure are used to develop a predictive critical heat flux (CHF) correlation for use in thermal management of electronic components. The configuration was that of a circular submerged jet impinging on a high-thermal-capacity copper surface with a standoff distance of 6 nozzle diameters. Varied parameters included the Reynolds numbers (Re) from 0 (pool boiling) to 14000, surface-to-nozzle diameter ratios (by varying the nozzle diameter) from 25 to 6, system pressures (0.2, 0.3, 0.5, 1 bar), surface roughness (123 nm, 33 nm), and system subcooling. CHF is found to increase with Re, system pressure, subcooling, and roughness and decreases with increase in nozzle diameter for a fixed Re. Comparison with correlations in literature indicated that data of sub-atmospheric jet impingement of water were poorly predicted by existing correlations while the Monde and Katto correlation [1] was found to predict the atmospheric jet impingement data with FC-72 within 10 percent at Re >4000. Data from the experiments were fitted to a submerged forced convective CHF model proposed by Haramura and Katto [2] to develop a correlation for submerged jet impingement boiling over a wide range of density ratios. Using this model, the entire CHF dataset from experiments can be predicted with a maximum error of less than 11 percent and an average error of less than 2.6 percent.

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