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Session 3233

A Nusselt Number Correlation Classification System

Craig W. Somerton, Laura J. Genik, Diana Beavers, Todd Jammer Department of Mechanical Engineering, Michigan State University/School of Engineering, University of Portland

I. Introduction

A main component of any undergraduate heat transfer course is the teaching of convective heat transfer and, in particular, the use of Nusselt number correlations to calculate convective heat transfer coefficients. Most of the standard heat transfer textbooks teach convection in a very compartmentalized way. There is normally a chapter on forced convection external flows, a chapter on forced convection internal flows, and a chapter on natural convection. This approach makes very good sense from the perspective of teaching students the physics of convective heat transfer; however, this does not follow a logical decision making process required for solving actual convective heat transfer problems. In actual heat transfer problems, the challenge is often in applying the appropriate judgment to identify the type of convective processes occurring in the situation. A disservice is done to the students if they are taught only from a compartmentalized perspective. They do not completely develop the judgment needed to solve actual heat transfer problems. A difficulty in teaching from a more integrated approach is the identification of the appropriate Nusselt number correlations once the nature of convective heat transfer process has been recognized. To address this concern a Nusselt number classification system has been developed.

There are examples of heat transfer classification systems that have appeared in the literature. One of the first of these is a convection coefficient classification by Lauer [1]. In this system, convection coefficients are classified and cataloged according to twenty two different geometries (e.g., Single Flat Vertical Surface-Vertical, Inside of Tubular Surface-Horizontal Tube, and Granular Solids), followed by six different thermal conditions (e.g., Cool Wall-Warm Gas, Cool Wall-Condensing Vapors, and Warm Wall-Cool Liquid), and finally by flow condition (natural convection, streamline flow, and turbulent flow). In fact it was this classification system and catalog that prompted the development of the system presented in this paper. Another example of a classification system in heat transfer is the transient heat conduction system proposed by Beck [2]. This a system that is used to classify different transient heat conduction problems and allows for the cataloging of analytical conduction solutions. Its basis is first identification of the coordinate system, Cartesian, cylindrical or spherical, followed by the type of boundary conditions specified for the problem. Finally, the form of the initial condition is specified. Using Beck’s numbering system the problem denoted by X13B01T0Y21B21 represents the physical problem of heat conduction in a two dimensional rectangular slab with a specified temperature boundary condition (1st kind boundary condition) at x = 0 and convective boundary condition (3rd kind boundary condition) at x = a. X13 tells us that we have rectangular coordinates with first and third kind boundary conditions along the x-coordinate. The boundary condition modifier B01 indicates that at x = 0 the specified temperature condition is T = 0 and

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Jammer, T., & Genik, L. J., & Beavers, D., & Somerton, C. W. (1999, June), A Nusselt Number Correlation Classification System Paper presented at 1999 Annual Conference, Charlotte, North Carolina. 10.18260/1-2--7861