Effect of variability of the physical parameters of a gravitational liquid film on its thickness and heat transfer during laminar flow

1984 ◽  
Vol 46 (6) ◽  
pp. 637-641
Author(s):  
G. I. Gimbutis ◽  
I. Yu. Reklaitis
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Liquid Film ◽  
Physical Parameters

Simulation of Sweating/Evaporation Boosted Convective Heat Transfer Under Laminar Flow Condition

2017 ◽  
Author(s):  
Sudipta Saha ◽  
Rajib Mahamud ◽  
Jamil Khan ◽  
Tanvir Farouk
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Film Thickness ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Water Film ◽  
The Heat Transfer Coefficient

Phase change driven heat transfer has been the topic of interest for a significantly long time. However, in recent years on demand sweating boosted evaporation which requires substantially less amount of the liquid medium has drawn attention as a possible way of increasing/supplementing heat transfer under convective conditions where the convective heat transfer coefficient has already reached its maximum value as well as where dry cooling is a desired objective. In this study, a numerical study is conducted to obtain insight into the ‘hybrid’ system where evaporation and convection both contribute to the heat transfer effect. The system modeled consists of evaporation of thin liquid (water) film under a laminar flow condition. The mathematical model employed consists of coupled conservation equations of mass, species, momentum and energy for the convection-evaporation domain (gaseous), with only mass and energy conservation being resolved in the liquid film domain. The evaporative mass flux is obtained from a modified Hertz-Knudsen relation which is a function of liquid-vapor interface temperature and pressure. A two-dimensional rectangular domain with a pre-prescribed thin liquid water film representative of an experiment is simulated with the developed model. The thin rectangular liquid film is heated by uniform heat flux and is placed in the convection-evaporation domain with an unheated starting length. A moving boundary mesh is applied via the“Arbitrary Lagrangian-Eulerian” technique to resolve the receding liquid interface resulting from evaporation. The prescribed relative displacement of the moving interface is calculated from the net mass flux due to evaporation and is governed by the principle of mass conservation. Simulations were conducted over a range of Reynolds number, heat flux conditions and liquid film thickness. The numerical predictions indicate that under convective-evaporative conditions the overall heat transfer coefficient increases significantly (∼factor of a five) in comparison to the purely forced convection scenario. An increase in the heat transfer coefficient is observed with Reynolds number and vice versa for film thickness. A critical Reynolds number is identified beyond which the heat transfer coefficient does not continue to increase significantly rather tends to plateau out.

MHD flow and heat transfer in a non-Newtonian liquid film over an unsteady stretching sheet with variable fluid properties

2009 ◽  
Vol 87 (10) ◽  
pp. 1065-1071 ◽  
Author(s):  
Mostafa A.A. Mahmoud ◽  
Ahmed M. Megahed
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Stretching Sheet ◽  
Variable Viscosity ◽  
Thin Liquid Film ◽  
Mhd Flow ◽  
Physical Parameters ◽  
Local Skin ◽  
Unsteady Stretching Sheet ◽  
Flow And Heat Transfer

The present paper is concerned with the study of variable viscosity and variable thermal conductivity on the flow and heat transfer of an electrically conducting non-Newtonian power-law fluid within a thin liquid film over an unsteady stretching sheet in the presence of a transverse magnetic field. The transformed system of nonlinear ordinary differential equations describing the problem is solved numerically. The effects of various parameters on the velocity and temperature profiles are shown through graphs and discussed. The values of the local skin-friction coefficient and the local Nusselt number for different values of physical parameters are presented through tables.

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