scholarly journals Experimental and Numerical Investigation of Micro/Mini Channel Flow-Boiling Heat Transfer with Non-Uniform Circumferential Heat Fluxes at Different Rotational Orientations

2020 ◽  
Vol 158 ◽  
pp. 119948
Author(s):  
M Vermaak ◽  
J Potgieter ◽  
J Dirker ◽  
M A Moghimi ◽  
P Valluri ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Channel Flow ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Flow Boiling Heat Transfer

Boiling Heat Transfer Performance in a Spiraling Radial Inflow Microchannel Cold Plate

2015 ◽  
Author(s):  
Maritza Ruiz ◽  
Claire M. Kunkle ◽  
Jorge Padilla ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Contact Angles ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Maximum Heat ◽  
Flow Boiling Heat Transfer

This study presents an experimental exploration of flow boiling heat transfer in a spiraling radial inflow microchannel heat sink. The effect of surface wettability, fluid subcooling levels, and mass fluxes are considered in this type of heat sink for use in applications with high fluxes up to 300 W/cm2. The design of the heat sink provides an inward radial swirl flow between parallel, coaxial disks that form a microchannel of 300 μm and 1 cm radius with a single inlet and a single outlet. The channel is heated on one side through a copper conducting surface, while the opposite side is essentially adiabatic to simulate a heat sink scenario for electronics cooling. Flow boiling heat transfer and pressure drop data were obtained for this heat sink device using water at near atmospheric pressure as the working fluid for inlet subcooling levels from 20 to 81°C and mean mass flux levels ranging from 184 to 716 kg/m2s. To explore the effects of varying surface wetting, experiments were conducted with two different heated surfaces. One was a clean, machined copper surface with water equilibrium contact angles in the range of 14–40°, typical of common metal surfaces. The other was a surface coated with zinc oxide nanostructures that are superhydrophilic with equilibrium contact angles measured below 10°. During boiling, increased wettability resulted in quicker rewetting and smaller bubble departure diameter as indicated by reduced temperature oscillations during boiling and achieving higher maximum heat flux without dryout. Reducing inlet subcooling levels was also found to reduce the magnitude of oscillations in the oscillatory boiling regime. The highest heat transfer coefficients were seen in fully developed boiling with low subcooling levels as a result of heat transfer being dominated by nucleate boiling. The highest heat fluxes achieved were during partial subcooled flow boiling at 300 W/cm2 with an average surface temperature of 134 °C and requiring a pumping power to heat rate ratio of 0.01%. The hydrophilic surface retained wettability after a series of boiling tests. Recommendations for use of this heat sink design in high flux applications is also discussed.

Prediction for Saturated Flow Boiling Heat Transfer in Mini-Channels

2013 ◽  
Author(s):  
Minxia Li ◽  
Chaobin Dang ◽  
Xing Fu ◽  
Yitai Ma
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Velocity Ratio ◽  
Heat Fluxes ◽  
Saturated Flow ◽  
Operation Conditions ◽  
Flow Boiling Heat Transfer ◽  
Wide Range ◽  
Mini Channels

A superposition correlation is proposed to predict heat transfer coefficient of flow boiling heat transfer in mini-channels. In this correlation, Reynolds number of liquid phase is presented by means of vapor velocity and slip velocity ratio. The film thickness and Bo number are taken account into this correlation. This new correlations were developed based on the conditions contained in our database. A database on experimental results of saturated-flow boiling in mini-channels includes 3839 data points, 9 different refrigerants, and covers a wide range of operation conditions from 10 independent studies. Most inner diameters in this database is within 0.5 mm and 3 mm and the mass fluxes in the database range from 50 to 600 kg /m2s, the heat fluxes from 5 to 123 kW/m2, the vapor qualities from 0 to 1, and the saturation temperatures from 0 to 52 °C. Research advances of flow boiling heat transfer in mini-channels in recent years were reviewed. 12 available flow boiling heat transfer correlations were addressed and evaluated against the database in this study. The proposed correlation can catch 77% data within the deviation of±30%. The mean absolute error of this new correlation is 20.9%.

Surface Roughness Effects on Flow Boiling in Microchannels

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
Benjamin J. Jones ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Pressure Drop ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer ◽  
Cut Surface

The influence of surface roughness on flow boiling heat transfer and pressure drop in microchannels is experimentally explored. The microchannel heat sink employed in the study consists of ten parallel, 25.4 mm long channels with nominal dimensions of 500×500 μm2. The channels were produced by saw-cutting. Two of the test piece surfaces were roughened to varying degrees with electrical discharge machining (EDM). The roughness average Ra varied from 1.4 μm for the as-fabricated, saw-cut surface to 3.9 μm and 6.7 μm for the two roughened EDM surfaces. Deionized water was used as the working fluid. The experiments indicate that the surface roughness has little influence on boiling incipience and only a minor impact on saturated boiling heat transfer coefficients at lower heat fluxes. For wall heat fluxes above 1500 kW/m2, the two EDM surfaces (3.9 μm and 6.7 μm) have similar heat transfer coefficients that were 20–35% higher than those measured for the saw-cut surface (1.4 μm). A modified Bertsch et al. [2009, “A Composite Heat Transfer Correlation for Saturated Flow Boiling in Small Channels,” Int. J. Heat Mass Transfer, 52, pp. 2110–2118] correlation was found to provide acceptable predictions of the flow boiling heat transfer coefficient over the range of conditions tested. Analysis of the pressure drop measurements indicates that only the roughest surface (6.7 μm) has an adverse effect on the two-phase pressure drop.

Experimental Study of Flow Boiling Heat Transfer in Mini-Tube

2005 ◽  
Author(s):  
Lihong Wang ◽  
Min Chen ◽  
Manfred Groll
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer

Flow boiling heat transfer characteristics of R134a were experimentally investigated in a horizontal stainless steel mini-tube. The inner diameter of the test tube is 1.3 mm and the tube wall thickness is 0.1 mm. Local heat transfer coefficients are obtained over a range of vapor qualities up to 0.8, mass fluxes from 310 to 860 kg/m2s, heat fluxes from 21 to 50 kW/m2, and saturation pressures from 6.5 to 7.5 bar. The mass flux, heat flux, saturation pressure, and vapor quality dependences of heat transfer coefficients are demonstrated. Based on an available model in recent literature potential heat transfer mechanisms are also analyzed.

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