Thick-Film Phenomenon in High-Heat-Flux Evaporation From Cylindrical Pores

1997 ◽  
Vol 119 (2) ◽  
pp. 272-278 ◽  
Author(s):  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Thick Film ◽  
High Heat ◽  
Liquid Films ◽  
Momentum Conservation ◽  
Vapor Flow ◽  
High Heat Flux ◽  
Operational Conditions ◽  
Flux Evaporation ◽  
Cylindrical Pores ◽  
Liquid Vapor

A physical and mathematical model of the evaporating thick liquid film, attached to the liquid-vapor meniscus in a circular micropore, has been developed. The liquid flow has been coupled with the vapor flow along the liquid-vapor interface. The model includes quasi-one-dimensional compressible steady-state momentum conservation for the vapor and also a simplified description of the microfilm at the end of the thick film. The numerical results, obtained for water, demonstrate that formation of extended thick liquid films in micropores can take place due to high-velocity vapor flow under high rates of vaporization. The model has also predicted that the available capillary pressure significantly changes with the wall-vapor superheat and other operational conditions.

The Influence of Evaporation in Shear-Driven Liquid Film on Heat Removal From Local Heater

2006 ◽  
Author(s):  
Elizaveta Gatapova ◽  
Oleg Kabov
Keyword(s):  
Liquid Film ◽  
Thin Liquid Film ◽  
Heat Removal ◽  
Film Surface ◽  
Numerical Data ◽  
High Heat ◽  
Liquid Films ◽  
High Heat Flux ◽  
Maximal Surface ◽  
High Heat Transfer

The present work focuses upon shear-driven liquid film evaporative cooling of high heat flux local heater. Thin evaporating liquid films may provide very high heat transfer rates and can be used for cooling of high power microelectronic systems. Thermocapillary convection in a liquid film falling down a locally heated substrate has recently been extensively studied. However, non-uniform heating effects remain only partially understood for shear-driven liquid films. The combined effects of evaporation, thermocapillarity and gas dynamics as well as formation of microscopic adsorbed film have not been studied. The effect of evaporation on heat and mass transfer for 2D joint flow of a liquid film and gas is theoretically and numerically investigated. The convective terms in the energy equations are taken into account. The calculations reveal that evaporation from film surface essential influences on heat removal from local heater. It is shown that the thermal boundary layer plays significant role for cooling local heater by evaporating thin liquid film. Measured by an infrared scanner temperature distribution at the film surface is compared with numerical data. Calculations satisfactorily describe the maximal surface temperature value.

Breakdown of a Locally Heated Liquid Film Shear-Driven in a Minichannel

2006 ◽  
Author(s):  
D. V. Zaitsev ◽  
O. A. Kabov
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
High Speed ◽  
Cooling System ◽  
Flow Regimes ◽  
High Heat ◽  
Liquid Films ◽  
High Heat Flux ◽  
Film Breakdown ◽  
High Heat Transfer

The paper focuses upon shear-driven liquid film evaporative cooling of high-speed computer chips. Thin liquid films may provide very high heat transfer rates, however development of cooling system based on thin film technology requires significant advances in fundamental research. The paper presents new experimental data on flow and breakdown of a liquid film driven by the action of a forced gas flow in a horizontal minichannel (2 mm high), heated from a 22×6.55 mm heater. A map of isothermal flow regimes is plotted and the lengths of smooth region and region of 2D/3D wave occurrence are measured. The scenario of liquid film breakdown under heating is found to differ widely for different flow regimes. It is revealed that the critical heat flux at which film breakdown occurs for a shear-driven liquid film can be several times higher than that for a gravitationally-driven liquid film. This fact makes shear-driven liquid films very promising in high heat flux cooling applications.

scholarly journals An experimental study of high heat flux removal by shear-driven liquid films

2017 ◽  
Vol 159 ◽  
pp. 00054 ◽  
Author(s):  
Dmitry Zaitsev ◽  
Egor Tkachenko ◽  
Oleg Kabov
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
High Heat ◽  
Liquid Films ◽  
High Heat Flux

Thermohydraulic Behavior of the Liquid–Vapor Flow in the Receiver Tube of a Solar Parabolic Trough Collector

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Sara Sallam ◽  
Mohamed Taqi
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Vapor Flow ◽  
High Heat Flux ◽  
Parabolic Trough ◽  
Convective Boiling ◽  
Flow Rates ◽  
Pressure Drops ◽  
Inlet Conditions ◽  
Liquid Vapor

Abstract Liquid–vapor flows are present in many industrial applications. In particular, in the solar field, these flows are encountered in the new generations of solar parabolic trough collectors with direct steam generation (PTCs-DSG). In this technical brief, we compare the two-phase convective transfer and the pressure drop models in the PTC-DSG. The results show that the heat exchange coefficients estimated by Chen–Cooper, Shah, Gungor–Winterton, and Kandlikar models have same trend with difference between them. However, the models of Liu–Winterton and Steiner–Taborek seem inappropriate due to the decrease in the exchange coefficient for moderate and high steam qualities. In addition, a comparison of the models describing pressure drops with experimental data of literature was carried out. The results show that the pressure decreases as the steam quality increases and the differences between these models remain small. Friedel's model is the closest to the experiment for high inlet pressures and flow rates, while Chisholm's model gives the best prediction of the pressure drop for low inlet conditions. Effect analysis of inlet conditions shows that the increase in inlet water mass flow and decrease in pressure favor convective heat transfer. The variation of heat flux on tube wall does not affect the convective boiling heat coefficient evaluated by the Chen–Copper model, whereas it influences the calculating coefficient by Gungor–Winterton model for high heat flux and particularly for low steam qualities. Pressure drops are higher at high flow rates and low pressures.

High Heat Flux Evaporation of Low Surface Tension Liquids from Nanoporous Membranes

2020 ◽  
Vol 12 (6) ◽  
pp. 7232-7238 ◽  
Author(s):  
Daniel F. Hanks ◽  
Zhengmao Lu ◽  
Jay Sircar ◽  
Ikuya Kinefuchi ◽  
Kevin R. Bagnall ◽  
...  
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
High Heat ◽  
High Heat Flux ◽  
Nanoporous Membranes ◽  
Flux Evaporation

Flow Patterns and CHF in a Locally Heated Liquid Film Shear-Driven in a Minichannel

2010 ◽  
Author(s):  
D. V. Zaitsev ◽  
O. A. Kabov
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
Gas Flow ◽  
Liquid Films ◽  
Vapor Flow ◽  
High Heat Flux ◽  
Film Rupture ◽  
Space Applications ◽  
Flow Rates ◽  
Wide Range

Thin and very thin (less than 10 μm) liquid films driven by a forced gas/vapor flow (stratified or annular flows), i.e. shear-driven liquid films in a narrow channel is a promising candidate for the thermal management of advanced semiconductor devices in earth and space applications. Development of such technology requires significant advances in fundamental research, since the stability of joint flow of locally heated liquid film and gas is a rather complex problem. The paper focuses on the recent progress that has been achieved by the authors through conducting experiments. Experiments with water in flat channels with height of H = 1.2–2.0 mm (mini-scale) show that a liquid film driven by the action of a gas flow is stable in a wide range of liquid/gas flow rates. Map of isothermal flow regime was plotted and the length of smooth region was measured. Even for sufficiently high gas flow rates an important thermocapillary effect on film dynamics occurs. Scenario of film rupture differs widely for different flow regimes. It is found that the critical heat flux for a shear driven film can be 10 times higher than that for a falling liquid film, and exceeds 400 W/cm2 in experiments with water for moderate liquid flow rates. This fact makes use of shear-driven liquid films promising in high heat flux chip cooling applications.

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