Why heat transfer coefficients are unnecessary and undesirable, and how heat transfer problems are solved without them.

Abstract

For 200 years, convective heat flux q has been calculated by multiplying heat transfer coefficient h times boundary layer temperature difference T. Since h times T equals q, h must be a symbol for (q/T) because (q/T) times T equals q. h (ie q/T) is generally calculated from correlations derived from experiments in which q data and T data are used to obtain (q/T){T} correlations-ie h{T} 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/T (ie h), and T can also be solved using only q and T. Therefore h (ie q/T) is unnecessary. h (ie q/T) is undesirable because, when q is a nonlinear function of T (as in free convection, condensation, and boiling), h (ie q/T) is an extraneous variable, and it greatly complicates problem solutions. When h has been abandoned, convective heat flux is determined from q{T} correlations that result from q data and T data, or from the transformation of h{T} correlations. (Transformation from h{T} correlations to q{T} correlations requires that h be replaced by q/T, and that q and T be separated.). The text includes example problems that validate the conclusion that h (ie q/T) is unnecessary and undesirable, and demonstrate that the solution of nonlinear problems is much simpler if h is abandoned.