Viscous Dissipation Effects on Combined Free and Forced Convection Through Vertical Circular Tubes

1970 ◽  
Vol 37 (4) ◽  
pp. 931-935 ◽  
Author(s):  
M. Iqbal ◽  
B. D. Aggarwala ◽  
M. S. Rokerya
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Viscous Dissipation ◽  
Transfer Rate ◽  
Circular Duct ◽  
Circular Tubes ◽  
Nusselt Numbers ◽  
Fluid Properties ◽  
Flow Phenomena ◽  
Free And Forced Convection

The effect of viscous dissipation on the flow phenomena and heat transfer rate in a vertical circular duct is analyzed for combined free and forced convection. All fluid properties are considered constant, except variation of density in the buoyancy term. It is noted that effect of viscous dissipation is to reduce the temperature differences in the system which in turn counteract the buoyancy effects. Therefore the viscous dissipation reduces the flow velocity near the wall and increases it near the tube center. Viscous dissipation effects reduce the Nusselt numbers. The reduction in Nusselt numbers is about six percent at the high values of the buoyancy rate (Rayleigh number = 1000) and the dissipation effect Eckert number/Reynolds number = 0.0005 was used in the present study.

Numerical Study of Forced Convection in Different Fluids From Stationary Heated Cylinders in a Square Enclosure

2018 ◽  
Author(s):  
Srishti Mishra ◽  
Mukul Tomar ◽  
Adeel Ahmad ◽  
Satvik Jain ◽  
Naveen Kumar
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Transfer Rate ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Flow Characteristics ◽  
Governing Equations ◽  
Square Enclosure ◽  
Nusselt Numbers ◽  
Fluid Properties

This paper performs a numerical study of forced convection heat transfer in a square enclosure with four identical stationary cylinders with single inlet and outlet ports. The ratio of the diameter of the cylinder to the length of the enclosure is kept constant at 0.1 with a fixed spacing between the cylinders. The enclosure walls are adiabatic while the cylinders are maintained at a constant temperature. The governing equations are solved for laminar, steady state and incompressible flow for different fluids namely air, water, and ethylene glycol. The study aims to determine the effect of varying Reynolds number (5 ≤ Re ≤ 100) and fluid properties (0.7 ≤ Pr < 200) on heat transfer rate and flow characteristics. The results of the study are presented in terms of streamlines, isotherm contours, and surface-averaged Nusselt numbers. The 2-D modeling and simulation have been conducted using ANSYS 16.0.

Effect of Entry Temperature on Forced Convection Heat Transfer With Viscous Dissipation in Thermally Developing Region of Concentric Annuli

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
M. M. J. Kumar ◽  
V. V. Satyamurty
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Viscous Dissipation ◽  
Numerical Solutions ◽  
Convection Heat Transfer ◽  
Radial Coordinate ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Nusselt Numbers ◽  
Circular Pipes

Steady laminar forced convection heat transfer in the thermal entrance region of concentric annuli has been studied considering viscous dissipation characterized by the Brinkman number. The inner and outer pipes have been kept at constant and equal temperature. Two cases of entry temperatures have been considered, case 1: an entry temperature that varies with the radial coordinate, obtained by an adiabatically prepared fluid, i.e., attained by the fluid due to viscous dissipation in an adiabatic concentric annular duct and case 2: the conventional uniform entry temperature. The numerical results presented include the nondimensional temperature profiles, Nusselt numbers, and heat transferred from (or to) the inner and outer pipes. It has been shown from the numerical solutions that it is necessary to employ the dissipative entry temperature in place of conventional uniform entry temperature for higher Brinkman numbers. The results for circular pipes follow when the radius ratio takes the limiting value of zero.

Combined Free and Forced Convection Through Vertical Rectangular Channels With Unequal Heating From Sides

1971 ◽  
Vol 38 (4) ◽  
pp. 829-833 ◽  
Author(s):  
M. Iqbal ◽  
B. D. Aggarwala
Keyword(s):  
Forced Convection ◽  
Unit Length ◽  
Heat Fluxes ◽  
The Body ◽  
Short Side ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Rectangular Channels ◽  
Fluid Properties ◽  
Free And Forced Convection

Fully developed laminar combined free and forced convection through vertical rectangular channels is studied. Uniform heat input per unit length is considered. All fluid properties are considered invariant with temperature except for the variation of density in the body-force term of the equation of motion. Broad sides of the duct are assumed at uniform temperature. The short sides have been treated for adiabatic condition; or under nonzero finite and even unequal heat fluxes. An exact solution of the problem has been presented. Nusselt numbers have been evaluated and their variation with respect to aspect ratios, buoyancy parameter, and short side heat fluxes have been studied.

scholarly journals Viscous dissipation effect on laminar forced convection in a circular duct with adiabatic walls - preliminary numerical investigation

2018 ◽  
Vol 240 ◽  
pp. 03016
Author(s):  
Tomasz Janusz Teleszewski
Keyword(s):  
Heat Flux ◽  
Forced Convection ◽  
Viscous Dissipation ◽  
Heat Flux Density ◽  
Energy Equation ◽  
Brinkman Number ◽  
Circular Duct ◽  
Nusselt Numbers ◽  
Axial Heat ◽  
Laminar Forced Convection

In this work, an analysis of laminar forced convection in a pipe with heated and adiabatic walls for a Newtonian fluid with constant properties is performed by taking the viscous dissipation into account when the axial heat conduction in the fluid is neglected. The Nusselt number versus the Brinkmann, which is based on the total wall heat flux density, have been investigated. In order to determine the temperature field, an analytical solution describing the velocity field in the pipe was used, while the energy equation was determined by the boundary element method (BEM). The results of the calculations of Nusselt numbers as a function of the Brinkman number for different thermal insulation heights to the diameter of the circular duct were presented in the form of diagrams.

Fully Developed Laminar Forced Convection in a Circular Duct for Herschel–Bulkley Fluids With Viscous Dissipation and Axial Heat Conduction

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Rabha Khatyr ◽  
Jaafar Khalid-Naciri ◽  
Ali Il Idrissi
Keyword(s):  
Boundary Condition ◽  
Heat Conduction ◽  
Forced Convection ◽  
Viscous Dissipation ◽  
Circular Duct ◽  
Nusselt Numbers ◽  
Asymptotic Values ◽  
Axial Heat ◽  
Laminar Forced Convection ◽  
Axial Heat Conduction

The asymptotic behavior of laminar forced convection in a circular duct for a Herschel–Bulkley fluid of constant properties is analyzed. The viscous dissipation and the axial heat conduction effects in the fluid are both considered. The asymptotic bulk and mixing temperature field, and the asymptotic values of the bulk and mixing Nusselt numbers are determined for every boundary condition, enabling a fully developed region. In particular, it is proved that whenever the wall heat flux tends to zero, the asymptotic Nusselt number is zero. The obtained results are compared to other existing solutions in the literature for Newtonian and non-Newtonian cases.

scholarly journals Analytical Assessment of (Al2O3–Ag/H2O) Hybrid Nanofluid Influenced by Induced Magnetic Field for Second Law Analysis with Mixed Convection, Viscous Dissipation and Heat Generation

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 498
Author(s):  
Wasim Ullah Khan ◽  
Muhammad Awais ◽  
Nabeela Parveen ◽  
Aamir Ali ◽  
Saeed Ehsan Awan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Viscous Dissipation ◽  
Entropy Generation ◽  
Heat Generation ◽  
Transfer Rate ◽  
Second Law ◽  
Hybrid Nanofluid ◽  
Entropy Generation Number ◽  
Generation Number ◽  
Second Law Analysis

The current study is an attempt to analytically characterize the second law analysis and mixed convective rheology of the (Al2O3–Ag/H2O) hybrid nanofluid flow influenced by magnetic induction effects towards a stretching sheet. Viscous dissipation and internal heat generation effects are encountered in the analysis as well. The mathematical model of partial differential equations is fabricated by employing boundary-layer approximation. The transformed system of nonlinear ordinary differential equations is solved using the homotopy analysis method. The entropy generation number is formulated in terms of fluid friction, heat transfer and Joule heating. The effects of dimensionless parameters on flow variables and entropy generation number are examined using graphs and tables. Further, the convergence of HAM solutions is examined in terms of defined physical quantities up to 20th iterations, and confirmed. It is observed that large λ1 upgrades velocity, entropy generation and heat transfer rate, and drops the temperature. High values of δ enlarge velocity and temperature while reducing heat transport and entropy generation number. Viscous dissipation strongly influences an increase in flow and heat transfer rate caused by a no-slip condition on the sheet.

Heat Transfer and Flow Phenomena in a Swirl Chamber Simulating Turbine Blade Internal Cooling

1998 ◽  
Author(s):  
C. R. Hedlund ◽  
P. M. Ligrani ◽  
H.-K. Moon ◽  
B. Glezer
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Internal Cooling ◽  
Vortex Pairs ◽  
Nusselt Numbers ◽  
Swirl Chamber ◽  
Flow Phenomena ◽  
Energy Balances

Heat transfer and fluid mechanics results are given for a swirl chamber whose geometry models an internal passage used to cool the leading edge of a turbine blade. The Reynolds numbers investigated, based on inlet duct characteristics, include values which are the same as in the application (18000–19400). The ratio of absolute air temperature between the inlet and wall of the swirl chamber ranges from 0.62 to 0.86 for the heat transfer measurements. Spatial variations of surface Nusselt numbers along swirl chamber surfaces are measured using infrared thermography in conjunction with thermocouples, energy balances, digital image processing, and in situ calibration procedures. The structure and streamwise development of arrays of Görtler vortex pairs, which develop along concave surfaces, are apparent from flow visualizations. Overall swirl chamber structure is also described from time-averaged surveys of the circumferential component of velocity, total pressure, static pressure, and the circumferential component of vorticity. Important variations of surface Nusselt numbers and time-averaged flow characteristics are present due to arrays of Görtler vortex pairs, especially near each of the two inlets, where Nusselt numbers are highest. Nusselt numbers then decrease and become more spatially uniform along the interior surface of the chamber as the flows advect away from each inlet.

scholarly journals Nusselt number evaluation for combined radiative and convective heat transfer in flow of gaseous products from combustion

2013 ◽  
Vol 17 (4) ◽  
pp. 1093-1106 ◽  
Author(s):  
Soraya Trabelsi ◽  
Wissem Lakhal ◽  
Ezeddine Sediki ◽  
Mahmoud Moussa
Keyword(s):  
Heat Transfer ◽  
Radiation Effects ◽  
Combustion Products ◽  
Radiative Properties ◽  
Inlet Temperature ◽  
Gaseous Products ◽  
Nusselt Numbers ◽  
Coupled Heat Transfer ◽  
Flow And Heat Transfer ◽  
Fluid Properties

Combined convection and radiation in simultaneously developing laminar flow and heat transfer is numerically considered with a discrete-direction method. Coupled heat transfer in absorbing emitting but not scattering gases is presented in some cases of practical situations such as combustion of natural gas, propane and heavy fuel. Numerical calculations are performed to evaluate the thermal radiation effects on heat transfer through combustion products flowing inside circular ducts. The radiative properties of the flowing gases are modeled by using the absorption distribution function (ADF) model. The fluid is a mixture of carbon dioxide, water vapor, and nitrogen. The flow and energy balance equations are solved simultaneously with temperature dependent fluid properties. The bulk mean temperature variations and Nusselt numbers are shown for a uniform inlet temperature. Total, radiative and convective mean Nusselt numbers and their axial evolution for different gas mixtures produced by combustion with oxygen are explored.

scholarly journals Analysis of Heat Transfer in Berman Flow of Nanofluids with Navier Slip, Viscous Dissipation, and Convective Cooling

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
O. D. Makinde ◽  
S. Khamis ◽  
M. S. Tshehla ◽  
O. Franks
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Viscous Dissipation ◽  
Perturbation Methods ◽  
Regular Perturbation ◽  
Convective Cooling ◽  
Navier Slip ◽  
Nusselt Numbers ◽  
Similarity Transformations ◽  
Friction Pressure Drop

Heat transfer characteristics of a Berman flow of water based nanofluids containing copper (Cu) and alumina (Al2O3) as nanoparticles in a porous channel with Navier slip, viscous dissipation, and convective cooling are investigated. It is assumed that the exchange of heat with the ambient surrounding takes place at the channel walls following Newton’s law of cooling. The governing partial differential equations and boundary conditions are converted into a set of nonlinear ordinary differential equations using appropriate similarity transformations. These equations are solved analytically by regular perturbation methods with series improvement technique and numerically using an efficient Runge-Kutta Fehlberg integration technique coupled with shooting scheme. The effects of the governing parameters on the dimensionless velocity, temperature, skin friction, pressure drop, and Nusselt numbers are presented graphically and discussed quantitatively.

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