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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Heat Transfer Coefficients for Tubes in the Turbulent Single Phase Flow Regime with a Focus on Uncertainty

Madder Steyn
University of Pretoria

Josua Petrus Meyer
Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, Private Bag X20, Hatfield, 0028, South Africa

DOI: 10.1615/IHTC15.fcv.009250
pages 3047-3061


KEY WORDS: Convection, Heat exchanger, Wilson plot, uncertainty analysis

Abstract

Predicting convective heat transfer inside tubes is a fundamental and critical part of the design of almost any thermodynamic system, yet many of the empirical formulations used to do so were proposed over 80 years ago and show a variance of up to 30%, without the authors having performed thorough uncertainty analyses. The Wilson plot method, and modifications thereof, has been the preferred method for separating the internal and annulus resistances up to now. While this method is relatively simple, difficulties in estimating its uncertainty necessitate the use of alternative methods if a more accurate and reliable correlation is to be found. The purpose of the study was to show that a new, more accurate, correlation for heat transfer coefficients inside round tubes could be formulated through direct measurement of the fluid and wall temperatures as well as careful application of the uncertainty analysis process. An initial estimation of this correlation was experimentally obtained through direct measurement of the heat transfer surfaces and using modern measurement equipment with water as the working fluid. Initial results verified the existing approximations in an averaged sense, but a local variance was observed. A new correlation, with an uncertainty of 6% is proposed. The contribution of individual sources of uncertainty to the overall uncertainty was investigated, and it was shown that the correct calculation of thermocouple uncertainty is vital in interpreting the obtained results

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