Integral relations for the interfacial heat and mass transfer resistivities and the inverted temperature gradient

2007 ◽  
Vol 19 (1) ◽  
pp. 017104 ◽  
Author(s):  
Eivind Johannessen ◽  
Dick Bedeaux
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Heat And Mass Transfer ◽  
Integral Relations

scholarly journals A microstructural dry-snow metamorphism model for kinetic crystal growth

2009 ◽  
Vol 55 (194) ◽  
pp. 1003-1011 ◽  
Author(s):  
D.A. Miller ◽  
E.E. Adams
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Heat And Mass Transfer ◽  
Growth Rates ◽  
Crystallographic Orientation ◽  
Thermal Conditions ◽  
Crystal Habit ◽  
Large Temperature ◽  
Kinetic Growth ◽  
Snow Metamorphism

AbstractHistorically, dry-snow metamorphism has been classified by the thermal environment and thermodynamic processes in a snowpack. Snow experiencing predominantly macroscopic isothermal conditions develops different microstructure than snow subjected to large temperature gradients. As such, much previous research has been categorized by and limited to specific thermal conditions. The current research expands a generalized approach for the movement of heat and mass to include a snow crystal kinetic growth model. An existing spiral defect propagation theory for kinetic growth on simple faceted geometry is utilized. Primary crystal habit as a function of temperature is incorporated. A model of heat and mass transfer through an ice and pore structure is coupled with phase-change thermodynamics during kinetic growth. A kinetic growth microstructure model is developed and integrated into heat and mass transfer representations, which are solved using finite-difference techniques. The kinetic morphology model approximates frequently observed hopper-type crystals. The snow microstructure is allowed to change at every step, resulting in a transient description of kinetic growth metamorphism. Variable kinetic growth rates are demonstrated based on temperature and on crystallographic orientation relative to a temperature gradient. Crystals preferentially aligned with the temperature gradient have significantly higher growth rates, supporting previous observations of predominant crystal habits developing under temperature gradient conditions. Grain-size dispersion increase with time is demonstrated and supported experimentally in the literature. A dominant grain growth theory based on crystallographic orientation that has been previously postulated is supported. A broad range of metamorphic geometric parameters and thermal conditions may now be simulated with a single model.

Experimental Study of Natural Convective Heat and Mass Transfer With Cross Diffusion Effects in Closed Cavity

2009 ◽  
Author(s):  
Wenguang Geng ◽  
Baoming Chen ◽  
Kai Sun ◽  
Li Wang ◽  
Fang Liu
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Heat And Mass Transfer ◽  
Indoor Environment ◽  
Convective Diffusion ◽  
Soret Effect ◽  
Concentration Gradients ◽  
Closed Cavity ◽  
Cross Diffusion ◽  
Diffusion Effects

Natural convective heat and mass transfer with Soret effect and Dufour effect is experimental studied in this paper to investigate the diffusion characteristic of volatile organic compounds (VOCs) in multi-physical fields. Firstly, Soret effect (thermal diffusion effect) experiment is conducted. The transfer process of isobutane and nitrogen in two close container connected by a small-diameter pipe is experimental studied. The results show that temperature difference between the two containers would conduct a solute concentration difference. Furthermore, multi-component convective diffusion experiment in a closed cavity which simulate indoor environment is developed under temperature gradient, humidity and propane gas concentration gradients. In this experiment, Temperature, humidity and concentration of propane could be surveyed real-time and do not interfere the natural convection in the closed cavity. The experiment results show that that the temperature gradient and the water vapor concentration gradient have effects on the convective diffusion of VOCs indoor environment. The cross diffusion effects would be taken into consideration for the problem of simultaneous heat and mass transfer especially in the presence of large temperature and concentration gradients.

scholarly journals Thermodynamics of non-isothermal diffusion at the extraction from cheese whey by Lupin

2019 ◽  
Vol 81 (3) ◽  
pp. 39-42
Author(s):  
Y. I. Shishackij ◽  
A. S. Belozercev ◽  
A. M. Barbashin ◽  
S. A. Nikel
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Differential Equations ◽  
Heat And Mass Transfer ◽  
Thermal Diffusion ◽  
Cheese Whey ◽  
Driving Forces ◽  
Extraction Process ◽  
The Body ◽  
Shape Sphere

In many cases, extraction is accompanied by thermal phenomena. We have established the possibility of intensifying the process through the use of heated cheese whey. Lupine has a geometric shape (sphere, cylinder, plate) loaded into an extractor filled with cheese whey. Due to the temperature difference between the solid and the liquid, temperature gradients are observed. As the body warms up, the temperature gradient decreases and then disappears. For example, an organized step temperature mode. However, such a regime should be technologically and energetically justified. Thus, during extraction there is a periodic non-stationarity. The emergence of this period is noted in the main works. The expression for the increase in entropy per unit time is written. Given the changes in entropy, the Gibbs equation is written. The basics of equations are the second laws of thermodynamics. As a result, the results obtained as a result of thermodynamic driving forces were obtained. The equations of energy (heat) and mass transfer of substances are written. Thermodynamic forces contribute to the formation of heat flux and mass flow of substances. The consumption of a substance depends not only on the gradient (diffusion), but also on the temperature gradient (thermal diffusion). Air temperature is defined as a temperature gradient. The differential equations of heat and mass transfer of Lykov were rewritten taking into account the extraction process. The numerical values of the coefficients Dт and aс they relate to the assessment of the effect of superposition effects (thermal diffusion and diffusion thermal conductivity). The overlay effect can be neglected, since the relatively small gradients of temperatures and concentrations arising in the lupine. It is noted that the possibility of simplified differential equations is associated with small values of the Lykov criterion. Because of this, there should be little.

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