American Journal of Mechanical Engineering
ISSN (Print): 2328-4102 ISSN (Online): 2328-4110 Website: http://www.sciepub.com/journal/ajme Editor-in-chief: Kambiz Ebrahimi, Dr. SRINIVASA VENKATESHAPPA CHIKKOL
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American Journal of Mechanical Engineering. 2020, 8(3), 106-110
DOI: 10.12691/ajme-8-3-2
Open AccessArticle

Why Heat Transfer Coefficients Are Unnecessary and Undesirable, and How Heat Transfer Problems Are Solved without Them

Eugene F. Adiutori1,

1Ventuno Press, 1094 Sixth Lane N., Naples, FL 34102

Pub. Date: September 17, 2020

Cite this paper:
Eugene F. Adiutori. Why Heat Transfer Coefficients Are Unnecessary and Undesirable, and How Heat Transfer Problems Are Solved without Them. American Journal of Mechanical Engineering. 2020; 8(3):106-110. doi: 10.12691/ajme-8-3-2

Abstract

For 200 years, convective heat flux q has been calculated by multiplying heat transfer coefficient h times boundary layer temperature difference ΔT. Since h times ΔT equals q, h must be a symbol for (q/ΔT) because (q/ΔT) times ΔT equals q. h (ie q/ΔT) is generally calculated from correlations derived from experiments in which q data and ΔT data are used to obtain (q/ΔT){ΔT} correlations-ie h{ΔT} correlations. (It is not possible to obtain h data because h is not a parameter. h is the ratio of two parameters). Heat transfer coefficients are unnecessary and undesirable. It is self-evident that any problem that can be solved using q, q/ΔT (ie h), and ΔT can also be solved using only q and ΔT. Therefore h (ie q/ΔT) is unnecessary. h (ie q/ΔT) is undesirable because, when q is a nonlinear function of ΔT (as in free convection, condensation, and boiling), h (ie q/ΔT) is an extraneous variable, and it greatly complicates problem solutions. When h has been abandoned, convective heat flux is determined from q{ΔT} correlations that result from q data and ΔT data, or from the transformation of h{ΔT} correlations. (Transformation from h{ΔT} correlations to q{ΔT} correlations requires that h be replaced by q/ΔT, and that q and ΔT be separated.). The text includes example problems that validate the conclusion that h (ie q/ΔT) is unnecessary and undesirable, and demonstrate that the solution of nonlinear problems is much simpler if h is abandoned.

Keywords:
dimensional homogeneity heat transfer coefficient law of convection heat transfer nonlinear problems parameter symbols

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References:

[1]  Newton, I., 1701, “A Scale of the Degrees of Heat”, Phil Trans Royal Soc (London), 22, p. 824.
 
[2]  Adiutori, E. F., 1990, “Origins of the Heat Transfer Coefficient”, Mechanical Engineering, August, pp 46-50.
 
[3]  Bejan, A., 2013, Convection Heat Transfer, 4th edition, Wiley, p. 32.
 
[4]  Fourier, J., (1822), The Analytical Theory of Heat, 1955 Dover edition of the 1878 English translation, The University Press, Article 36.