Thermal constriction resistance of a contact on a circular cylinder with mixed convective boundaries

1988 ◽  
Vol 420 (1859) ◽  
pp. 323-354 ◽  
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Thermal Contact ◽  
Circuit Board ◽  
Asperity Contact ◽  
Convective Boundary ◽  
Aspect Ratios ◽  
Constriction Resistance ◽  
Plane Face ◽  
Wide Range

Numerous important heat-transfer problems make use of a cylinder as the basic element: these include the conduction of heat between two bodies in asperity contact; the heat transfer in a convectively cooled printed circuit board; the thermal analysis of fin coolers. This paper presents a unified treatment of the steady-state axisymmetric temperature distribution in a cylinder of radius b and height h . Thermal contact occurs over a circle of radius a (≼ b ) on the top plane face of the cylinder, and is governed by a general convective boundary condition. The remainder of the top plane face, the curved surface and the bottom may be insulated, isothermal, or subject to other convective boundary conditions. If the boundary conditions on the two parts of the top surface are unmixed, the problem is reduced by Hankel, Fourier and Abel transform techniques to a quadrature and the summation of an infinite series. If they are mixed, the problem is reduced to the solution of an integro-differential equation. Extensive numerical results are presented for the thermal constriction resistance over a wide range of dimensionless Biot numbers and aspect ratios b / a and h / a .

A New Model for Constriction Resistance of Rough Contacts between Nominally Flat Surfaces

2011 ◽  
Vol 110-116 ◽  
pp. 977-984
Author(s):  
Jun Feng Peng ◽  
Jun Hong ◽  
Yan Zhuang
Keyword(s):  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Rough Surfaces ◽  
Thermal Contact ◽  
Radial Distance ◽  
Asperity Contact ◽  
Flat Surfaces ◽  
Constriction Resistance ◽  
Nonlinear Curve Fitting ◽  
Wide Range

Thermal contact resistance plays an important role in many domains, such as microelectronics and nuclear reactors. This paper proposes a more comprehensive model for the prediction of constriction resistance of rough contact between nominally flat surfaces in vacuum. Firstly, a 3D geometrical asperity contact model is proposed based on the analysis of the profile of actual engineering surface. In this model, the contact is not simplified as a rough surface contacting with a perfectly smooth surface, but described as two rough surfaces. Oblique contact is considered and the effects of several parameters such as the shape of the asperity, the depth of interference, and the radial distance between the centerlines of the contacting asperities are investigated. Some mathematical derivations for constriction resistance are performed, and a series of numerical simulations are also carried out, covering a wide range of values of these parameters in practice applications. A comprehensive correlation for constriction resistance as a function of these parameters is finally obtained by nonlinear curve fitting, and it is validated through some comparisons and it can be used to predict more accurately the thermal contact resistance between rough surfaces.

Unsteady and porous media flow of reactive non-Newtonian fluids subjected to buoyancy and suction/injection

2015 ◽  
Vol 25 (7) ◽  
pp. 1682-1704 ◽  
Author(s):  
Tirivanhu Chinyoka ◽  
Daniel Oluwole Makinde
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Boundary Conditions ◽  
Flow Velocity ◽  
Flow System ◽  
Finite Difference Methods ◽  
Porous Media Flow ◽  
Convective Boundary Conditions ◽  
Convective Boundary ◽  
Content Type

Purpose – The purpose of this paper is to examine the unsteady pressure-driven flow of a reactive third-grade non-Newtonian fluid in a channel filled with a porous medium. The flow is subjected to buoyancy, suction/injection asymmetrical and convective boundary conditions. Design/methodology/approach – The authors assume that exothermic chemical reactions take place within the flow system and that the asymmetric convective heat exchange with the ambient at the surfaces follow Newton’s law of cooling. The authors also assume unidirectional suction injection flow of uniform strength across the channel. The flow system is modeled via coupled non-linear partial differential equations derived from conservation laws of physics. The flow velocity and temperature are obtained by solving the governing equations numerically using semi-implicit finite difference methods. Findings – The authors present the results graphically and draw qualitative and quantitative observations and conclusions with respect to various parameters embedded in the problem. In particular the authors make observations regarding the effects of bouyancy, convective boundary conditions, suction/injection, non-Newtonian character and reaction strength on the flow velocity, temperature, wall shear stress and wall heat transfer. Originality/value – The combined fluid dynamical, porous media and heat transfer effects investigated in this paper have to the authors’ knowledge not been studied. Such fluid dynamical problems find important application in petroleum recovery.

Heat Transfer in a Couple Stress Fluid over a Continuous Moving Surface with Internal Heat Generation and Convective Boundary Conditions

2012 ◽  
Vol 67 (5) ◽  
pp. 217-224 ◽  
Author(s):  
Tasawar Hayat ◽  
Zahid Iqbal ◽  
Muhammad Qasim ◽  
Omar M. Aldossary
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Heat Generation ◽  
Couple Stress ◽  
Couple Stress Fluid ◽  
Physical Parameters ◽  
Series Solutions ◽  
Convective Boundary Conditions ◽  
Convective Boundary ◽  
Moving Surface

This investigation reports the boundary layer flow and heat transfer characteristics in a couple stress fluid flow over a continuos moving surface with a parallel free stream. The effects of heat generation in the presence of convective boundary conditions are also investigated. Series solutions for the velocity and temperature distributions are obtained by the homotopy analysis method (HAM). Convergence of obtained series solutions are analyzed. The results are obtained and discussed through graphs for physical parameters of interest.

ENTRANCE EFFECTS OF THERMAL CREEP ON FLUID HEATING IN RECTANGULAR MICROCHANNELS

2013 ◽  
Vol 24 (08) ◽  
pp. 1350054 ◽  
Author(s):  
ALI AMIRI-JAGHARGH ◽  
HAMID NIAZMAND ◽  
METIN RENKSIZBULUT
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Temperature Jump ◽  
Velocity Slip ◽  
Temperature Gradients ◽  
Thermal Creep ◽  
Constant Wall Temperature ◽  
Rectangular Microchannels ◽  
Aspect Ratios ◽  
Wide Range

The effects of thermal creep on the development of gaseous fluid flow and heat transfer in rectangular microchannels with constant wall temperature are investigated in the slip-flow regime. Thermal creep arises from tangential temperature gradients, which may be significant in the entrance region of channels, and affects the velocity and temperature fields particularly in low Reynolds number flows. In the present work, the Navier–Stokes and energy equations coupled with velocity-slip and temperature-jump conditions applied at the channel walls are solved numerically using a control-volume technique. Despite the constant wall temperature, tangential temperature gradients form in the gas layer adjacent to the wall due to the temperature-jump condition. The effects of slip/jump and thermal creep on the flow patterns and parameters are studied in detail for a wide range of channel aspect ratios and, Knudsen and Reynolds numbers. Furthermore, the effects of variable properties on velocity-slip and, friction and heat transfer coefficients are also examined.

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