Entropy Generation in Convective Heat Transfer and Isothermal Convective Mass Transfer

1987 ◽  
Vol 109 (3) ◽  
pp. 647-652 ◽  
Author(s):  
J. Y. San ◽  
W. M. Worek ◽  
Z. Lavan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Boundary Conditions ◽  
Convective Heat Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Entropy Generation ◽  
Ideal Gas ◽  
Convective Mass Transfer ◽  
Plate Spacing

The irreversible generation of entropy for two limiting cases of combined forced-convection heat and mass transfer in a two-dimensional channel are investigated. First, convective heat transfer in a channel with either constant heat flux or constant surface temperature boundary conditions are considered for laminar and turbulent flow. The entropy generation is minimized to yield expressions for optimum plate spacing and optimum Reynolds numbers for both boundary conditions and flow regimes. Second, isothermal convective mass transfer in a channel is considered, assuming the diffusing substance to be an ideal gas with Lewis number equal to unity. The flow is considered to be either laminar or turbulent with boundary conditions at the channel walls of either constant concentration or constant mass flux. The analogy between heat and mass transfer is used to determine the entropy generation and the relations for optimum plate spacing and Reynolds number. The applicable range of the results for both limiting cases are then investigated by non-dimensionalizing the entropy generation equation.

Double Diffusive Magnetohydrodynamic (MHD) Natural Convection and Entropy Generation in a Discretely Heated Inclined Dome-Shaped Enclosure Filled with Cu-Water Nanofluid

2021 ◽  
Vol 10 (4) ◽  
pp. 564-579
Author(s):  
Rujda Parveen ◽  
Priyajit Mondal ◽  
Tapas Ray Mahapatra
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Entropy Generation ◽  
Inclination Angle ◽  
Hartmann Number ◽  
Substantial Impact ◽  
Double Diffusive

This research presents an investigation of laminar two-dimensional double-diffusive free convection and entropy formation in an inclined enclosure under the influence of an inclined magnetic field. The performance of natural convective heat transfer can be improved by doing modifications in enclosure geometry that impact the flow structure. We have considered a dome-shaped enclosure to examine the heat and mass transfer performance. The enclosure is saturated with Cu-water nanofluid and the two sidewalls of the enclosure are maintained at constant temperature Tc(<Th) and concentration cc(<ch). The top-curved wall is adiabatic, and the lower wall is discretely heated and concentrated. The governing equations are first non-dimensionalized and then written in stream function-velocity formulation that is solved numerically using the Bi-CGStab method. A comparison with previously published work in literature is presented and found to be in excellent agreement. Numerical simulations are performed for various values of considered parameters such as Rayleigh number (Ra), Hartmann number (Ha), the orientation of magnetic field (γ), volume fraction of nanoparticles (Φ), and inclination angle of the enclosure (δ). The mentioned parameters have a substantial impact on the cavity flow characteristics. The obtained results demonstrate that the average Sherwood number and Nusselt number are decreasing functions of both the Hartmann number and inclination angle of the enclosure. The minimum heat and mass transfer took place at δ = 135° as the angle of inclination of the enclosure restrains the fluid velocity and reduces the heat transfer rate. Also, entropy generation analysis is conducted for all the considered parameters. The results show that the dome-shaped enclosure has a substantial impact on the fluid flow that enables a smoother and more effective flow inside the cavity, which improves the natural convective heat and mass transmission.

scholarly journals Effect of corrugated minichannel variable width on entropy generation for convective heat transfer of alpha-Alumina-water nanofluid

2021 ◽  
Vol 2053 (1) ◽  
pp. 012016
Author(s):  
N M Muhammad ◽  
N A C Sidik ◽  
A Saat ◽  
Y Asako ◽  
W M A A Japar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Entropy Production ◽  
Convective Heat ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Thermal Systems ◽  
Volume Fractions ◽  
Thermal Entropy ◽  
Alpha Alumina

Abstract Energy management and sustainability in thermal systems require maximum utilization of resources with minimal losses. However, it is rarely unattainable due to the ever-increasing need for a high-performance system combined with device size reduction. The numerical study examined convective heat transfer of an alpha-Alumina-water nanofluid in variable-width corrugated minichannel heat sinks. The objective is to study the impact of nanoparticle volume fractions and flow area variation on the entropy generation rate. The determining variables are 0.005 – 0.02 volume fractions, the fluid velocity 3 – 5.5 m/s and heat flux of 85 W/cm2. The numerical results show an acceptable correlation with the experiment results. The results indicate the thermal entropy production drop with an increase in nanoparticles volume fraction. Contrastingly, the frictional resistance entropy suggests the opposite trend due to the turbulence effect on the fluid viscosity. The induction of Alumina-Water nanofluid with enhanced thermal conductivity declined the entropy generation rate compared to water alone. The increase in width ratio by 16% between the cases translates to at least a 9% increase in thermal entropy production. The outcome of this study can provide designers and operators of thermal systems more insight into entropy management in corrugated heatsinks.

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