Flow Boiling in Microgaps for Thermal Management of High Heat Flux Microsystems

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Xuefei Han ◽  
Andrei Fedorov ◽  
Yogendra Joshi
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Experimental Studies ◽  
High Heat ◽  
Bubble Nucleation ◽  
Inlet Temperature ◽  
High Heat Flux ◽  
Two Phase ◽  
Outlet Pressure

In the first part of this paper, a review of fundamental experimental studies on flow boiling in plain and surface enhanced microgaps is presented. In the second part, complimentary to the literature review, new results of subcooled flow boiling of water through a micropin-fin array heat sink with outlet pressure below atmospheric are presented. A 200 μm high microgap device design was tested, with a longitudinal pin pitch of 225 μm, a transverse pitch of 135 μm, and a diameter of 90 μm, respectively. Tested mass fluxes ranged from 1351 to 1784  kg/m2s, and effective heat flux ranged from 198 to 444 W/cm2 based on the footprint surface area. The inlet temperature varied from 6 to 12 °C, and outlet pressure ranged from 24 to 36 kPa. The two-phase heat transfer coefficient showed a decreasing trend with increasing heat flux. High-speed visualizations of flow patterns revealed a triangular wake after bubble nucleation. Flow oscillations were seen and discussed.

Flow Boiling of Sub-Cooled Pentane on a Micro-Porous Coating

2012 ◽  
Author(s):  
Paul J. Laca ◽  
Richard A. Wirtz
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
High Performance ◽  
Flow Boiling ◽  
High Heat ◽  
Surface Coatings ◽  
Porous Coating ◽  
High Heat Flux ◽  
Characteristic Curves ◽  
High Speed Video

Flow boiling experiments with sub-cooled Isopentane and n-Pentane at 3.0bar pressure assess the utility of compressed copper- and steel-filament screen laminate surface coatings as high performance boiling surfaces. High-speed video show that at high heat flux ebullition is unsteady. Isopentane and n-Pentane are found to produce nearly identical boiling characteristic curves. At the same applied heat flux, the superheat of copper filament coatings are much smaller than the steel filament coating superheats.

High heat flux flow boiling in silicon multi-microchannels – Part III: Saturated critical heat flux of R236fa and two-phase pressure drops

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5426-5442 ◽  
Author(s):  
Bruno Agostini ◽  
Rémi Revellin ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Flux Flow ◽  
Pressure Drops ◽  
Phase Pressure

Effect of Gravitational Orientation on Flow Boiling of Water in 1054 × 197 µm Parallel Minichannels

2004 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Operating Conditions ◽  
Microgravity Environment ◽  
High Heat Flux ◽  
Two Phase ◽  
Mass Fluxes ◽  
Heat Transfer Degradation

Microchannels and minichannels are being considered for high heat flux applications under microgravity environment in space missions. An experimental study is undertaken to determine the effect of gravitational orientation on flow boiling characteristics of water in a set of six parallel minichannels, each 1054 μm wide by 197 μm deep and 63.5 mm long with a hydraulic diameter of 333 μm. Three orientations — horizontal, vertical downflow and vertical upflow — are investigated under identical operating conditions of heat and mass fluxes. High-speed images are obtained to reveal the detailed two-phase flow structure and liquid-vapor interactions. The experimental data and high speed flow visualization indicate that compared to the horizontal case, the flow becomes less chaotic for vertical upflow, while the reversed flow becomes more pronounced in vertical downflow case. The resulting in increase in the back-flow is responsible for channel-to-channel flow maldistribution and heat transfer degradation. From the heat transfer data it is concluded that the performance of the tested channels under microgravity environment will be similar to the horizontal flow case.

An Experimental Investigation of Sub-Cooled Flow Boiling in Hypervapotron Cooling Configuration

2004 ◽  
Author(s):  
Peipei Chen ◽  
Barclay G. Jones ◽  
Ty A. Newell
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
Experimental Studies ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Subcooled Boiling ◽  
Reduced Pressure

This work reports on experimental studies to visualize nucleate boiling on the enhanced heat transfer surface of the hypervapotron for with application in the International Thermonuclear Experiment Reactor [ITER]. This research uses the simulant fluid Freon (R134A) instead of prototypic water to model the system performance. This results in much lower thermophysical conditions to represent the prototypic phenomena. By using reduced pressure, temperatures, etc, based on the critical physical properties of both working fluids, Freon and water, the dramatic drop in the level of these quantities with Freon allows the use of modest test conditions. The experiment was conducted for both saturated and subcooled boiling with different heat fluxes (from 50 to 300 kW/m2). A comparison of the heat transfer performance of finned structures and flat surfaces were examined under particular fluid conditions. The uniqueness of this work is the visualization method that allows direct observation of the subcooled boiling process of the Hypervapotron surfaces. Working with a high speed (12,000 frames per second), high fidelity digital camera with variable magnifications (from 1×–25×), the sub-cooled boiling phenomena was observed in detail. A major conclusion of this work is the existence of two separate zones linked to different energy removal efficiency in hypervapotron. Under high heat flux condition, enhanced boiling heat transfer (about 20–30% higher than flat surface) was observed for hypervapotron effect, while saturated boiling happened in the cavity, and a large portion of the region was vapor filled. The process of vapor bubble rotation in the slot appeared to be helpful to enhance energy transfer, as evidenced by an improved wetting condition on the heating surfaces.

Flow Boiling Heat Transfer Enhancement in Subcooled and Saturated Refrigerants in Minichannel Heat Sinks

2014 ◽  
Author(s):  
Ehsan Yakhshi-Tafti ◽  
Howard Pearlman ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Sinks ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Laser Applications ◽  
Enhanced Boiling

Forced two-phase cooling is investigated for handling high power electronics and laser applications having high heat flux and isothermality requirements. Experimental results are reported for minichannel heat sinks with and without enhanced boiling coatings showing increased heat transfer coefficients and higher critical heat flux for coated versus uncoated surfaces.

A Review of High-Heat-Flux Heat Removal Technologies

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
M. A. Ebadian ◽  
C. X. Lin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Heat Removal ◽  
High Heat ◽  
High Heat Flux ◽  
Phase Flow ◽  
Two Phase ◽  
Recent Developments ◽  
Removal Technologies

In recent years, high-heat-flux cooling techniques have received great attention from researchers around the world due to its importance in thermal management of both commercial and defense high-power electronic devices. Although impressive progress has been made during the last few decades, high-heat-flux removal still largely remains as a challenging subject that needs further exploration and study. In this paper, we have reviewed recent developments in several high-heat-flux heat removal techniques, including microchannels, jet impingements, sprays, wettability effects, and piezoelectrically driven droplets. High-heat-flux removal can be achieved effectively by either single-phase flow or two-phase flow boiling heat transfer. Better understandings of the underlying heat transfer mechanisms for performance improvement are discussed.

Two-Phase Cooling Characteristics of Mono-Dispersed Droplets Impacted on a Heated Surface

2011 ◽  
Author(s):  
S. R. Mahmoudi ◽  
K. Adamiak ◽  
G. S. P. Castle
Keyword(s):  
Heat Flux ◽  
Impact Velocity ◽  
Heated Surface ◽  
Experimental Studies ◽  
Volumetric Flow Rate ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Mass Fluxes ◽  
The Impact

Droplet impact cooling has been shown to be a promising method for high heat flux removal applications. Recent experimental studies have revealed that even higher heat transfer at low mass fluxes and low Weber number can be achieved with only few degrees of superheat. In the present work, mono-dispersed droplet cooling of a horizontal upward facing heated surface was investigated at low Weber numbers. The impact velocity and frequency of free falling stream of droplets were varied dependently through changing the gap between the heated surface and tip of different capillaries and variation of volumetric flow rate (0.5–4.7 cc/min).The range of impact velocity and droplet frequency was ranged between 0.28 to 1.3 m/s and 0.5 Hz to 5 Hz, respectively using different capillaries size between 17g to 22g. The coolant was 25°C deionized water and all the experiments were performed at atmospheric pressure. The time-averaged two-phase characteristic curves were obtained up to Critical Heat Flux (CHF)-regime. Through the extensive set of experiments, two separate correlations are proposed to predict the average CHFs based on the Weber between 3<We<10, 10<We<100 and Strouhal number ranged and 6.35×10−3<St<3.88×10−2 1.81×10−3<St<3.86×10−2, respectively. The correlation predicts the average CHFs with absolute errors less than 20% and 25%, respectively.

An Experimental Study on the Effect of Gravitational Orientation on Flow Boiling of Water in 1054×197μm Parallel Minichannels

2005 ◽  
Vol 127 (8) ◽  
pp. 820-829 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Operating Conditions ◽  
Microgravity Environment ◽  
High Heat Flux ◽  
Two Phase ◽  
Heat Transfer Degradation

Microchannels and minichannels are being considered for high heat flux applications under microgravity environment in space missions. An experimental study is undertaken to determine the effect of gravitational orientation on flow boiling characteristics of water in a set of six parallel minichannels, each 1054μm wide by 197μm deep and 63.5mm long with a hydraulic diameter of 333μm. Three orientations—horizontal, vertical downflow, and vertical upflow—are investigated under identical operating conditions of heat and mass fluxes. High-speed images are obtained to reveal the detailed two-phase flow structure and liquid-vapor interactions. The experimental data and high speed flow visualization indicate that compared to the horizontal case, the flow becomes less chaotic for the vertical upflow case, while the reversed flow becomes more pronounced in the vertical downflow case. The resulting increase in the backflow is responsible for channel-to-channel flow maldistribution and heat transfer degradation. From the heat transfer data it is concluded that the performance of the tested channels in a microgravity environment will be similar to the horizontal flow case.

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