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.

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.

An Interferometric Study of Combined Free and Forced Convection in a Horizontal Isothermal Tube

1981 ◽  
Vol 103 (2) ◽  
pp. 249-256 ◽  
Author(s):  
W. W. Yousef ◽  
J. D. Tarasuk
Keyword(s):  
Nusselt Number ◽  
Free Convection ◽  
Forced Convection ◽  
Average Nusselt Number ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Horizontal Tube ◽  
Reynolds Numbers ◽  
Nusselt Numbers ◽  
Free And Forced Convection

A Mach-Zehnder interferometer was employed to determine the three-dimensional temperature field, and the circumferential and average Nusselt numbers for laminar flow of air in the entrance region of an isothermal horizontal tube where the velocity and the temperature profiles were developing simultaneously. The influence of free convection due to buoyancy on forced convection heat transfer was investigated. The Reynolds numbers ranged from 120 to 1200, the Grashof numbers ranged from 0.8 × 104 to 8.7 × 104, and the ratio L/D was varied from 6 to 46. The free convection increases, substantially, the average Nusselt number, by up to a factor of 2.0 from the analytical predictions, which account for forced convection only, near the tube inlet. Far from the tube inlet the free convection tends to decrease the average Nusselt number below the analytical predictions.

On the Conjugate Problem of Laminar Combined Free and Forced Convection through Vertical Non-Circular Ducts

1972 ◽  
Vol 94 (1) ◽  
pp. 52-56 ◽  
Author(s):  
M. Iqbal ◽  
B. D. Aggarwala ◽  
A. K. Khatry
Keyword(s):  
Heat Conduction ◽  
Laminar Flow ◽  
Forced Convection ◽  
Small Variation ◽  
Conjugate Problem ◽  
Momentum Equation ◽  
Variational Technique ◽  
Fluid Properties ◽  
Free And Forced Convection ◽  
Axial Heat

The present analysis deals with the conjugate problem of combined free and forced convection through vertical non-circular ducts. The equations coupling heat conduction in the walls with the convection inside the fluid are solved to establish the influence of peripheral wall conduction, using variational technique. Fully developed laminar flow with uniform axial heat input and constant fluid properties, except for the small variation of density in the buoyancy term of the momentum equation, is assumed. The problem has been solved in a generalized way and the results have been presented for rectangular ducts. It is found that large values of the free convection effects and/or of the conduction parameter tend to minimize the asymmetries in circumferential wall temperature.

Transient, Laminar, Combined Free and Forced Convection in a Duct

1962 ◽  
Vol 84 (2) ◽  
pp. 141-148 ◽  
Author(s):  
S. L. Zeiberg ◽  
W. K. Mueller
Keyword(s):  
Steady State ◽  
Forced Convection ◽  
Wall Temperature ◽  
Axial Direction ◽  
Transient Heating ◽  
Fully Developed Flow ◽  
Fluid Properties ◽  
Free And Forced Convection ◽  
Approach To Steady State ◽  
Rayleigh Numbers

Transient, laminar, combined free and forced convection in a duct is analyzed under the assumptions of constant fluid properties, and fully developed flow. The transient heating is taken to be a result of wall temperature variations; the wall temperatures vary linearly with the axial co-ordinate of the duct (this is shown to be the only permissible axial dependence, other than no wall temperature variation in the axial direction). Numerical results show that for certain combinations of the Prandtl and Rayleigh numbers, an oscillatory approach to steady state exists. This phenomenon can induce a large reduction of the Nusselt number (compared to steady state) during the transient period.

Numerical Solution for Combined Free and Forced Laminar Convection in Horizontal Rectangular Channels

1969 ◽  
Vol 91 (1) ◽  
pp. 59-66 ◽  
Author(s):  
K. C. Cheng ◽  
Guang-Jyh Hwang
Keyword(s):  
Numerical Solution ◽  
Axial Position ◽  
Uniform Wall Temperature ◽  
Thermal Boundary Conditions ◽  
Aspect Ratios ◽  
Rectangular Channels ◽  
Free And Forced Convection ◽  
Uniform Wall ◽  
Laminar Convection ◽  
Uniform Wall Heat Flux

Combined free and forced convection for steady fully developed laminar flow in horizontal rectangular channels under the thermal boundary conditions of axially uniform wall heat flux and peripherally uniform wall temperature at any axial position is approached by the method of successive overrelaxation. The convergence of the numerical solution is ascertained. Graphical results are presented for streamlines, isotherms, w/w0 versus Re Ra, f Re/(f Re)0 versus Re Ra, and Nu/Nu0 versus Re Ra for the aspect ratios γ = 0.2, 0.5, 1, 2, and 5 and Pr = 0.73. For square channels, velocity and temperature distributions for Pr = 0.73 and heat transfer results for Pr = 7.2 are also presented.

scholarly journals Heat Transfer Around Sharp 180 Degree Turns in Smooth Rectangular Channels

1985 ◽  
Author(s):  
D. E. Metzger ◽  
M. K. Sahm
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Side Wall ◽  
Bottom Wall ◽  
Channel Depth ◽  
Nusselt Numbers ◽  
Rectangular Channels

Measured Nusselt numbers are presented for forced convection within and around sharp 180 degree turns in smooth channels of rectangular cross section. Separately determined top wall, bottom wall, and side wall values are presented individually along with azimuthal averages. The geometry of the channels and connecting turn is characterized by parameters W*, the ratio of upstream and downstream channel widths; D*, the non-dimensional channel depth; and H*, the non-dimensional clearance at the tip of the turn. Results from nine combinations of these parameters are presented at several values of channel Reynolds number to illustrate the effect of turn geometry on the heat transfer distributions.

Heat Transfer Around Sharp 180-deg Turns in Smooth Rectangular Channels

1986 ◽  
Vol 108 (3) ◽  
pp. 500-506 ◽  
Author(s):  
D. E. Metzger ◽  
M. K. Sahm
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Side Wall ◽  
Bottom Wall ◽  
Channel Depth ◽  
Nusselt Numbers ◽  
Rectangular Channels

Measured Nusselt numbers are presented for forced convection within and around sharp 180-deg turns in smooth channels of rectangular cross section. Separately determined top wall, bottom wall, and side wall values are presented individually along with azimuthal averages. The geometry of the channels and connecting turn is characterized by the parameters W*, the ratio of upstream and downstream channel widths; D*, the nondimensional channel depth; and H*, the nondimensional clearance at the tip of the turn. Results from nine combinations of these parameters are presented at several values of channel Reynolds number to illustrate the effect of turn geometry on the heat transfer distributions.

An Analytical Solution of the Effect of Peripheral Wall Conduction on Laminar Forced Convection in Rectangular Channels

1965 ◽  
Vol 87 (1) ◽  
pp. 59-66 ◽  
Author(s):  
R. Siegel ◽  
J. M. Savino
Keyword(s):  
Heat Conduction ◽  
Forced Convection ◽  
Wall Temperature ◽  
Energy Equation ◽  
Side Wall ◽  
Transverse Wall ◽  
Short Side ◽  
Rectangular Channels ◽  
Side Walls ◽  
Laminar Forced Convection

This study deals with fully developed laminar forced convection in rectangular channels that are heated on the broad sides. The analysis determines the effect of peripheral heat conduction within the heated walls on the wall temperature distributions. The unheated short side walls are assumed nonconducting. The heat conduction within the broad walls was formulated in terms of an integral equation and coupled with the convective energy equation within the fluid. Analytical solutions were obtained where the heating extends over the entire width of the broad side, is removed from the corner region, or extends beyond the corner into the side wall. Transverse wall conduction produced substantial decreases in the peak wall temperature and in the temperature gradients along the long side.

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.

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