Extended Surface Heat Transfer

2001 ◽  
Vol 54 (5) ◽  
pp. B92-B92 ◽  
Author(s):  
AD Kraus, ◽  
A Aziz, ◽  
J Welty, ◽  
DP Sekulic,
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Extended Surface

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.

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

Windows-Based Portable Laboratory System for Demonstrating Heat Transfer From an Extended Surface

2001 ◽  
Author(s):  
Mohammad Khosrowjerdi ◽  
Said Dini ◽  
James Aflaki
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Surface Heat ◽  
Laboratory System ◽  
Heat Transfer Characteristics ◽  
Surface Heat Transfer ◽  
Service Unit ◽  
Transfer Characteristics ◽  
Laboratory Courses ◽  
Extended Surface

Abstract An Armfield™ small bench top service unit (HT10X) in conjunction with an extended surface heat transfer assembly (HT15) are utilized to demonstrate the temperature profile and heat transfer characteristics of a cylindrical rod. Heat flows along the rod by conduction and is lost to the surroundings by combined natural convection and radiation. This well-instrumented laboratory teaching equipment allows students to measure the temperature distribution along the rod and compare the result with a theoretical analysis. Also, heat transfer from the extended surface resulting from the combined modes of free convection and radiation heat transfer is investigated. A self-contained Windows-based data collection and analysis system has been developed for automating all the manual functions of the Armfield™ extended surface heat transfer assembly; HT15. This system uses an inexpensive plug-in data acquisition board to read the voltage signals corresponding to nine K-type thermocouples and heater supplied voltage and current. The user interface software that is written in Visual Basic 6 uses 32-bit libraries to control the heater voltage and read the thermocouples voltages and heater supplied voltage and current. Used in conjunction with the HT15 unit, the software is a valuable teaching tool for instructors and provides a comprehensive learning environment within which heat transfer characteristics can be studied. It is aimed at enhancing the students understanding of one dimensional heat conduction along a cylindrical rod and enabling them to contrast theory and practical measurements of temperatures. It is also the intent of this paper to discuss the successful integration of this educational system into portable instructional technology for the classroom and the mechanical engineering laboratory courses.

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