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.

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.

Submerged Jet Impingement Boiling of Saturated Water Under Sub-Atmospheric Conditions

2010 ◽  
Author(s):  
Ruander Cardenas ◽  
Preeti Mani ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Internal Diameter ◽  
Atmospheric Conditions ◽  
Submerged Jet ◽  
Surface Distance ◽  
Saturated Water ◽  
Jet Impingement Boiling

An experimental study of mini-jet impingement boiling is presented for saturated conditions. Unique to this study is documentation of boiling characteristics of a submerged water jet under sub-atmospheric conditions. Data are reported at a fixed nozzle-to-surface distance that corresponds to a monotonic decrease in heat transfer coefficient for single-phase jet impingement. A mini nozzle is used in the present study with an internal diameter of 1.16 mm. Experiments are performed at three sub-atmospheric pool pressures of 0.2 bar, 0.3 bar and 0.5 bar. At each pressure, jet impingement boiling at four Reynolds numbers are characterized and compared with the pool boiling heat transfer. Enhancements in critical heat flux with increasing Re are observed for all pressures.

Confined Submerged Jet Impingement Boiling of Subcooled FC-72 over Micro-Pin-Finned Surfaces

2015 ◽  
Vol 37 (3-4) ◽  
pp. 269-278 ◽  
Author(s):  
Yonghai Zhang ◽  
Jinjia Wei ◽  
Xin Kong ◽  
Ling Guo
Keyword(s):  
Jet Impingement ◽  
Submerged Jet ◽  
Jet Impingement Boiling

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.

Effects of Fluid Viscosity and Impingement Angle on Submerged Jet Flowfields

2018 ◽  
Author(s):  
Soroor Karimi ◽  
Matthew Fulton ◽  
Siamack A. Shirazi ◽  
Brenton McLaury
Keyword(s):  
Maximum Velocity ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Fluid Viscosity ◽  
Impingement Angle ◽  
Submerged Jet ◽  
Glass Spheres ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Experiments

Many researchers have utilized submerged jet impingement geometry to study solid particle erosion/corrosion. However, only a few studies have investigated changing impingement angle and fluid viscosity. In this study, Particle Image Velocimetry (PIV) experiments were conducted using 14 micron glass spheres for direct impingement geometry at viscosities of 1, 14, and 55 cP. These viscosities correspond to Reynolds numbers of approximately 57000, 4000, and 1000, respectively. It was observed that by increasing the viscosity the flow exiting the nozzle transitioned from extremely turbulent to laminar flow. The data indicated fully turbulent flow at the outlet for viscosities of 1 and 14 cP. In the case of 55 cP flow, the flow exiting the nozzle became laminar contributing to a higher maximum velocity in 55 cP flow. Experiments at these viscosities were also conducted at impingement angles of 90, 75, and 45 degrees to investigate the effects of the impinging jet angle on a flat plate. Additionally, a series of Computational Fluid Dynamics (CFD) simulations of the flowfield were performed to compare with the experimental data collected in this paper.

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.

Microstructured Surfaces for Single-Phase Jet Impingement Heat Transfer Enhancement

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Gilberto Moreno ◽  
Sreekant Narumanchi ◽  
Travis Venson ◽  
Kevin Bennion
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Surface Roughening ◽  
Submerged Jet ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Microstructured Surfaces ◽  
Microporous Coating

An experimental investigation was conducted to examine the use of microstructured surfaces to enhance jet impingement heat transfer. Three microstructured surfaces were evaluated: a microfinned surface, a microporous coating, and a spray pyrolysis coating. The performance of these surface coatings/structures was compared to the performance of simple surface roughening techniques and millimeter-scale finned surfaces. Experiments were conducted using water in both the free- and submerged-jet configurations at Reynolds numbers ranging from 3300 to 18,700. At higher Reynolds numbers, the microstructured surfaces were found to increase Nusselt numbers by 130% and 100% in the free- and submerged-jet configurations, respectively. Potential enhancement mechanisms due to the microstructured surfaces are discussed for each configuration. Finally, an analysis was conducted to assess the impacts of cooling a power electronic module via a jet impingement scheme utilizing microfinned surfaces.

Suitability Evaluation of Bubble Departure Diameter and Frequency Models for the Simulation of Subcooled Confined Jet Impingement Boiling

2014 ◽  
Author(s):  
S. Abishek ◽  
R. Narayanaswamy ◽  
V. Narayanan
Keyword(s):  
Heat Transfer ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Jet Impingement ◽  
Operating Conditions ◽  
Accurate Estimation ◽  
Momentum Exchange ◽  
Ansys Fluent ◽  
Suitability Evaluation ◽  
Jet Impingement Boiling

Accurate estimation of multiphase turbulence, interphase momentum exchange and bubble dynamics parameters such as bubble departure diameter and frequency is critical for a realistic simulation of flow boiling heat transfer. While there are experimental and mechanistic models available for the estimation of these parameters for rather specific geometric configurations, fluids and operating conditions, there is no specific comprehensive model for jet impingement boiling. Nor is there a consensus on a generalized model, particularly for the ebullition parameters, that could be extended to jet impingement boiling. Hence, a problem-based evaluation of the available models to conform to experimental data is often required. In the present work, a rigorous study is carried out to ascertain the suitability of different bubble departure diameter and departure frequency models for the simulation of confined and submerged, subcooled jet impingement boiling. The choice of ebullition models considered encompass both pool boiling as well as flow boiling based models, developed from both experimental as well as mechanistic approaches. The suitability of the models are evaluated by comparison of the predicted local and surface averaged heat transfer characteristics against experimental boiling data from the present research as well as that available in the literature. The computational simulations are carried out using the finite volume computational solver ANSYS FLUENT 14.5, with necessary customized functions for boiling parameters formulated and integrated into the solver.

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.

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