Heat and fluid flow from a wavy surface subjected to a 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.

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Magnetohydrodynamic Fluid Flow due to an Unsteady Stretching Sheet with Thermal Radiation, Porous Medium, and Variable Heat Flux

Advances in Astronomy ◽

10.1155/2021/6686883 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Ahmed M. Megahed ◽

Nourhan I. Ghoneim ◽

M. Gnaneswara Reddy ◽

Mostafa El-Khatib

Keyword(s):

Heat Flux ◽

Fluid Flow ◽

Thermal Radiation ◽

Stretching Sheet ◽

Variable Viscosity ◽

Unsteady Stretching Sheet ◽

Variable Heat ◽

Variable Heat Flux ◽

Conductivity Parameter ◽

Efficient Heat Transfer

A shooting method has been introduced for determining the numerical solution of the ordinary differential equations which describe the Newtonian magnetohydrodynamic laminar fluid flow due to an unsteady stretching sheet together with the presence of thermal radiation and variable heat flux. The variable viscosity and variable conductivity are taken into consideration. Absence of magnetic field in some studies restricts the development of the energy-efficient heat transfer mechanism as is desired in numerous applications. The present study encompasses parameters such as unsteadiness parameter, porous parameter, viscosity parameter, magnetic number, radiation parameter, and conductivity parameter. It has been consummated that the proposed model is superior to other existing models for the industrial fluid.

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

The Journal of Supercritical Fluids ◽

10.1016/j.supflu.2012.12.010 ◽

2013 ◽

Vol 74 ◽

pp. 115-127 ◽

Cited By ~ 17

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

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

Modern Physics Letters B ◽

10.1142/s0217984916501554 ◽

2016 ◽

Vol 30 (16) ◽

pp. 1650155 ◽

Cited By ~ 9

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.

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