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.

Enhanced Forced Convection Heat Transfer From a Cylinder Using Permeable Fins

2003 ◽  
Vol 125 (5) ◽  
pp. 804-811 ◽  
Author(s):  
Bassam A/K Abu-Hijleh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Cross Flow ◽  
Horizontal Cylinder ◽  
Convection Heat ◽  
Transfer Rates ◽  
Forced Convection Heat Transfer ◽  
Nusselt Numbers

The problem of cross-flow forced convection heat transfer from a horizontal cylinder with multiple, equally spaced, high conductivity permeable fins on its outer surface was investigated numerically. The heat transfer characteristics of a cylinder with permeable versus solid fins were studied for several combinations of number of fins and fin height over the range of Reynolds number (5–200). Permeable fins provided much higher heat transfer rates compared to the more traditional solid fins for a similar cylinder configuration. The ratio between the permeable to solid Nusselt numbers increased with Reynolds number and fin height but tended to decrease with number of fins. This ratio was as high as 4.35 at Reynolds number of 150 and a single fin with a nondimensional height of 3.0. The use of 1–2 permeable fins resulted in much higher Nusselt number values than when using up to 18 solid fins. Such an arrangement has other benefits such as a considerable reduction in weight and cost.

Forced Convection Heat Transfer in a Finitely Conducting Externally Finned Pipe

1988 ◽  
Vol 110 (3) ◽  
pp. 571-576 ◽  
Author(s):  
F. Moukalled ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Axial Direction ◽  
Bulk Temperature ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Nusselt Numbers ◽  
Wall Conductivity

A numerical study to determine the influence of axial wall conduction on forced convection heat transfer in an externally finned pipe has been made. The effects of wall conductivity, interfin spacing, and external heat transfer coefficient are examined by comparing the results with the corresponding solutions obtained assuming negligible wall conduction. Results indicate that the axial conduction in the pipe walls has a significant influence on the heat transfer behavior. The bulk temperature or the heat transferred to the fluid is underestimated when wall conduction is ignored. At high wall conductivity values, the wall temperatures and Nusselt numbers exhibit a monotonic variation in the axial direction, with the behavior becoming increasingly nonmonotonic as the wall conductivity value is decreased.

Laminar Forced Convection Heat Transfer in Spherical Annuli

1983 ◽  
Vol 105 (2) ◽  
pp. 341-349 ◽  
Author(s):  
S. Ramadhyani ◽  
M. M. Torbaty ◽  
K. N. Astill
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Outer Sphere ◽  
Flow Patterns ◽  
Convection Heat ◽  
Complex Flow ◽  
Forced Convection Heat Transfer ◽  
Nusselt Numbers ◽  
Spherical Surfaces

An analysis is presented of forced convection heat transfer in spherical annuli bounded by isothermal surfaces at different temperatures. Flow enters the annulus through a port in the outer sphere and exits through a diametrically opposite port. The conservation equations of mass, momentum, and energy are reduced to dimensionless form, and the governing parameters of the problem are identified. Solutions are obtained for several values of each of the governing parameters via a numerical finite-difference procedure. It is found that very complex flow patterns can prevail within the annulus, particularly at high Reynolds numbers. Details of the flow field are presented by means of velocity and pressure profile plots. The effect of the flow patterns on the heat transfer phenomena is discussed by examining temperature profiles and variations of the local Nusselt number along the spherical surfaces. In addition, the circumferential average Nusselt numbers at the two spherical surfaces are presented as functions of the governing parameters of the problem. These graphs of average Nusselt numbers constitute information that could be used in the design of spherical annulus heat transfer equipment.

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