Natural convection on a vertical plate with variable heat flux in supercritical fluids

2013 ◽  
Vol 74 ◽  
pp. 115-127 ◽  
Author(s):  
Ali Reza Teymourtash ◽  
Danyal Rezaei Khonakdar ◽  
Mohammad Reza Raveshi
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Supercritical Fluids ◽  
Vertical Plate ◽  
Variable Heat ◽  
Variable Heat Flux

scholarly journals Heat transfer in natural convection flow of nanofluid along a vertical wavy plate with variable heat flux

2019 ◽  
Vol 23 (1) ◽  
pp. 179-190 ◽  
Author(s):  
Irfan Mustafa ◽  
Tariq Javed
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Pure Water ◽  
Wavy Surface ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Local Skin ◽  
Variable Heat ◽  
Variable Heat Flux

The present analysis is concerned to examine the enhancement of heat transfer in natural convection flow of nanofluid through a vertical wavy plate assumed at variable heat flux. The rate of heat transfer in nanofluid flow as compared to pure water can be increased due to increase the density of nanofluid which depends on the density and concentration of nanoparticles. For this analysis, Tiwari and Das model is used by considering two nanoparticles i. e. Al2O3 and Cu are suspended in a base fluid (water). A very efficient implicit finite difference technique converges quadratically is applied on the concerning PDE for numerical solution. The effects of pertinent parameters namely, volume fraction parameter of nanoparticle, wavy surface amplitude, Prandtl number and exponent of variable heat flux on streamlines, isothermal lines, local skin friction coefficient and local Nusselt number are shown through graphs. In this analysis, a maximum heat transfer rate is noted in Cu-water nanofluid through a vertical wavy surface as compared to Al2O3-water and pure water.

scholarly journals Modeling and simulation of natural convection flow along a rough surface of sinusoidal nature with variable heat flux: Using Keller box scheme

2019 ◽  
Vol 23 (6 Part A) ◽  
pp. 3391-3400
Author(s):  
Abuzar Ghaffari ◽  
Tariq Javed ◽  
Irfan Mustafa ◽  
Fotini Labropulu
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Natural Convection ◽  
Skin Friction Coefficient ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Local Skin ◽  
Variable Heat ◽  
Variable Heat Flux ◽  
Local Skin Friction

In this study, natural convection flow along a vertical wavy surface has been investigated with variable heat flux. The governing equations are transformed into dimensionless PDE by using the non-dimensional variables and then solved numerically by using an implicit finite difference scheme known as Keller Box method. The effects of the parameters amplitude of the wavy surface, ?, exponent of the variable heat flux, m, and Prandtl number on the local skin friction coefficient and local Nusselt number are shown graphically. It is found that for the negative value of exponent of the variable heat flux, m, the local skin friction coefficient increases and Nusselt number decreases but the opposite behavior is observed for the positive values of m. The comparison of limiting case with the previous study is shown through table and it is found that the solution obtained is in excellent agreement with the previous studies.

Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

2016 ◽  
Vol 30 (16) ◽  
pp. 1650155 ◽  
Author(s):  
Ebrahim Afshari ◽  
Masoud Ziaei-Rad ◽  
Nabi Jahantigh
Keyword(s):  
Heat Flux ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Pressure Drop ◽  
Flow Field ◽  
Pem Fuel Cells ◽  
Coolant Flow ◽  
Temperature Uniformity ◽  
Variable Heat ◽  
Variable Heat Flux

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

Sign in / Sign up

Export Citation Format

Share Document