Heat Transfer Through an Extended Surface Containing He II

1999 ◽  
Vol 121 (1) ◽  
pp. 142-147 ◽  
Author(s):  
S. W. Van Sciver
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Analytic Solution ◽  
Heat Transfer Process ◽  
Surface Heat ◽  
Bulk Fluid ◽  
Kapitza Conductance ◽  
Extended Surface ◽  
Tube Type ◽  
Special Case

A semi-analytic solution for the heat transfer process between a He II pressurized bath and a saturated tube-type heat exchanger is presented. The problem is modeled with an extended surface heat transfer formulation analogous to that in conventional conduction. The process is governed by Kapitza conductance and counterflow within the bulk fluid in the tube. The resulting nonlinear differential equation may be integrated for the special case of constant properties, yielding a simple solution applicable to design and analysis of practical heat exchangers.

On the Transiant Response of Convective Extended Surface Heat Transfer: A New Approach

2006 ◽  
Author(s):  
P. Razelos ◽  
G. Michalakeas
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Transient Response ◽  
Surface Heat ◽  
Constant Thickness ◽  
Conduction Model ◽  
Steady State Condition ◽  
Surface Heat Transfer ◽  
Extended Surface ◽  
Extended Surfaces

This work is devoted to the study of the extended surfaces transient response. Although, the steady-state fin analysis has attracted considerable attention for a very long time, the interest in the transient response started in the last quarter of the past century. Several publications have appeared since, either analytical using the 1-D, conduction model, or experimental. Perusing the pertinent literature, however, we have observed that, in all previous published papers the authors treat the transient response of extended surfaces, or fins, like regular solids. However, fin endeavors rest on certain fundamental concepts, leading to some simplified assumptions, that we shall briefly discuss in the next section, which allows using the 1-D conduction model, and affect their steady-state operation. Therefore, the need for re-examining and revising the previously used methods becomes apparent. However, the authors are indebted to the pioneer workers on this topic that opened new avenues in the field of extended surface heat transfer. The aim of this work is to offer a different point of view to this problem, by introducing a new spatial coordinate system, and a new time scale. The solutions presented here, rest on the previously mentioned certain fundamental concepts developed recently. In the following we show step by step, how the existing pertinent equations and formulas of fins' transient response, are transformed to new simpler forms, expressed in terms of more appropriate dimensionless parameters, in accord with those appearing in recent publications. In the following, we confine to the analysis of constant thickness longitudinal and pin fins subject to specific1 boundary conditions. Each case is accompanied with an example that, for reasons of comparison are taken from the literature. We also discuss what is meant by "the time required for transient response to attain the steady-state condition."

Fundamental Concepts and an Innovating Approach for Extended Surface Heat Transfer

2005 ◽  
Author(s):  
Panagiotis Razelos
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Vital Role ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Novel Approach ◽  
Mathematical Expressions ◽  
Extended Surface ◽  
Simplifying Assumptions ◽  
The One

In this work we re-examine the main fin equation qf = ηfAfΔT, proposed by Gardner [1] that has been used for the last sixty years to determine the performance of fins. The fundamental concepts of extended surface heat transfer are introduced, and their mathematical expressions are derived. The vital role of fin effectiveness, a term also introduced by Gardner [1] is established. It is shown that the effectiveness is inextricably linked in proving the validity of the simplifying assumptions that most of the fins’ endeavors are based on. It is also shown that the common practice of using the efficiency to predict the fin’s performance leads to serious errors. A novel approach to fin analysis, based on a proposed transformation of coordinates, is presented, which can be employed to considerably simplify the pertinent differential equations and obtain more friendly expressions describing the fin’s performance. The heat dissipation is expressed in a non-dimensional form and for several practical cases polynomial expressions have developed, that will help students to engage in rudimentary fin designs. It is also shown that, the one-dimensional approach can be used to obtain solutions involving extended surfaces made from anisotropic material. Three examples serve to illustrate the usefulness of our method.

Numerical Computation of the Effects of Brownian Motion on the Effective Thermal Conductivity of Suspensions

2007 ◽  
Author(s):  
P. E. Phelan ◽  
J. R. Pacheco
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Dimensional Space ◽  
Numerical Technique ◽  
Heat Transfer Process ◽  
Immersed Boundary ◽  
Brownian Dynamic ◽  
Dynamic Simulations ◽  
Bulk Fluid

In this paper, a numerical scheme based on the immersed boundary method is used to study the motion of nano-sized particles subjected to Brownian motion and heat transfer. Our objective is to use this numerical technique as a tool to better understand the effect that Brownian forces have on the overall heat transfer process. The conventional approach to perform Brownian dynamic simulations is based on the use of a random force in the particle motion such that the fluctuation-dissipation theorem is satisfied. Our preliminary computational results suggest an increase in the thermal conductivity of the bulk fluid. Results are presented for several particles in a two-dimensional space.

Sixty-Five Years of Extended Surface Technology (1922–1987)

1988 ◽  
Vol 41 (9) ◽  
pp. 321-364 ◽  
Author(s):  
Allan D. Kraus
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Electronic Equipment ◽  
Numerical Analyses ◽  
Compact Heat Exchangers ◽  
Extended Surface ◽  
Mathematical Techniques

The extended surface literature from 1922 to 1987 is reviewed. The review begins with the classic NACA report of Harper and Brown published in 1922 and concludes with the works of Marto, Wanniarachchi, Rose, Mitrou, and Razelos published in 1986. A section entitled “The Beginnings” traces the accomplishments of the pioneers and it covers the period from 1922 to 1945 which coincides with the publication of Gardner’s landmark paper. At this point, a chronological approach is abandoned in favor of a categorization into topical areas. These are the elimination of the Murray–Gardner assumptions, boiling and condensation, experimental endeavors, compact heat exchangers, internally finned configurations, numerical analyses, optimizations, analyses of finned arrays, and additional topics including the use of extended surface to augment heat transfer, heat transfer in electrical and electronic equipment, purely mathematical techniques, and heat and mass transfer.

Extended Surface Heat Transfer

2000 ◽  
Author(s):  
Allan D. Kraus ◽  
Abdul Aziz ◽  
James Welty
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Extended Surface
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