Probing the temperature profile across a liquid–vapor interface upon phase change

2020 ◽  
Vol 153 (14) ◽  
pp. 144706
Author(s):  
Arif Rokoni ◽  
Ying Sun
Keyword(s):  
Phase Change ◽  
Temperature Profile ◽  
Vapor Interface ◽  
Liquid Vapor

Experimental Studies of Nonisothermal Binary Fluids With Phase Change in Confined Geometries

2012 ◽  
Author(s):  
Yaofa Li ◽  
Benjamin M. Chan ◽  
Minami Yoda
Keyword(s):  
Surface Tension ◽  
Mass Transport ◽  
Phase Change ◽  
Experimental Studies ◽  
Liquid Density ◽  
Binary Fluids ◽  
Vapor Interface ◽  
Evaporation And Condensation ◽  
Alcohol Water ◽  
Liquid Vapor

Evaporative cooling, which exploits the large latent heats associated with phase change, is of interest in a variety of thermal management technologies. Yet our fundamental understanding of thermal and mass transport remains limited. Evaporation and condensation can change the local temperature, and hence surface tension, along a liquid-vapor interface. The resulting thermocapillary stresses are dominant at small length scales in many cases. For the vast majority of single-component coolants, surface tension decreases as temperature increases, resulting in thermocapillary stresses that drive the liquid away from hot regions, leading to dryout, for example. The direction of flow driven by thermocapillary stresses is therefore consistent with that driven by buoyancy effects due to changes in the liquid density with temperature. However, a number of binary “self-rewetting fluids,” consisting of water-alcohol mixtures, have surface tensions that increase with temperature, leading to thermocapillary stresses that drive liquid towards hot regions, improving cooling performance. Although not all binary coolants are self-rewetting, all such coolants are subject to solutocapillary stresses, where differential evaporation of the two fluid components leads to changes in local species concentration at the liquid-vapor interface, and hence in surface tension. Given the lack of general models of thermal and mass transport in nonisothermal two-phase flows, experimental studies of convection in simple fluids and binary alcohol-water mixtures due to evaporation and condensation driven by a horizontal temperature gradient were performed. In these initial studies, both the simple and binary fluids have thermocapillary stresses that drive liquid away from hot regions. However, the binary fluid also has solutocapillary stresses that drive liquid towards hot regions. Particle-image velocimetry (PIV) is used to nonintrusively measure the velocity and temperature fields in a layer of liquid a few mm in depth in a 1 cm × 1 cm × 4.85 cm sealed and evacuated cuvette heated on one end and cooled on the other end.

Effect of Vapor Superheating on Mixed-Convection Film Condensation Along an Isothermal Vertical Cylinder

2010 ◽  
Vol 26 (1) ◽  
pp. N1-N7 ◽  
Author(s):  
T.-B. Chang
Keyword(s):  
Mixed Convection ◽  
Temperature Profile ◽  
Vapor Phase ◽  
Vertical Cylinder ◽  
Forced Flow ◽  
Film Condensation ◽  
Marginal Effect ◽  
Vapor Interface ◽  
Condensate Layer ◽  
Liquid Vapor

AbstractThis paper presents an analytical investigation into the effect of vapor superheating on the mixed-convection of a condensate layer flowing along the outside surface of an isothermal vertical cylinder. The governing system of partial differential equations is transformed into a dimensionless form using the nonsimilar transformation method. In investigating the heat transfer characteristics within the condensate layer and vapor phase, the analysis takes account of both the inertia effects and the convection effects within the condensate layer and the shear resistance at the liquid-vapor interface. The numerical results reveal that vapor superheating has a negligible effect on the temperature profile and local Nusselt number within the condensate layer. Moreover, it is found that a higher forced-flow intensity increases the temperature gradient in the vapor phase, but has a marginal effect on the temperature profile in the condensate layer. Finally, it is shown that the velocity at the liquid-vapor interface increases as the intensity of the forced-flow increases or as the ratio of the condensate layer viscosity to the vapor phase viscosity reduces.

Two-Phase Flow With Phase Change in Porous Channels

2015 ◽  
Vol 7 (2) ◽  
Author(s):  
Gaurav Tomar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Phase Change ◽  
Heat Pipes ◽  
Porous Channel ◽  
Two Phase ◽  
Vapor Interface ◽  
Interface Location ◽  
Heat Loads ◽  
Liquid Vapor

Phase change heat transfer in porous media finds applications in various geological flows and modern heat pipes. We present a study to show the effect of phase change on heat transfer in a porous channel. We show that the ratio of Jakob numbers based on wall superheat and inlet fluid subcooling governs the liquid–vapor interface location in the porous channel and below a critical value of the ratio, the liquid penetrates all the way to the extent of the channel in the flow direction. In such cases, the Nusselt number is higher due to the proximity of the liquid–vapor interface to the heat loads. For higher heat loads or lower subcooling of the liquid, the liquid–vapor interface is pushed toward the inlet, and heat transfer occurs through a wider vapor region thus resulting in a lower Nusselt number. This study is relevant in the designing of efficient two-phase heat exchangers such as capillary suction based heat pipes where a prior estimation of the interface location for the maximum heat load is required to ensure that the liquid–vapor interface is always inside the porous block for its operation.

A Numerical Description of a Liquid-Vapor Interface Based on the Second Gradient Theory

1995 ◽  
Vol 22 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Didier Jamet ◽  
Olivier Lebaigue ◽  
Jean-Marc Delhaye ◽  
N. Coutris
Keyword(s):  
Gradient Theory ◽  
Vapor Interface ◽  
Second Gradient ◽  
Liquid Vapor
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