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

Eugene F. Adiutori^1,

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

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

This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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.