The Reynolds analogy between the coefficients of heat transfer and wall shear can be suggested on the basis of the following simple analysis. (a) Divide the expression for shear stress T = P(v + m) by the expression for heat flux du dy q = p ( + H) dT dy to obtain Tw CP (1 9w TCP 9 (b) Assume that the molecular and turbulent Prandtl numbers are unity so that the velocity and temperature profiles are nearly the same and du/Dt=const. Replace the left-hand side by wall values and then integrate to obtain h pCUv v + m du a + EH dT (Tmax - Twall) = (Umax = (Umax - Uwall) (c) Set T = (Cf/2)pU and qw=h(Tmixing Uav 2 Umax cup Tmixing cup - Twall) to obtain Tmax - Twall Twall Uwall Tmixing cup - - which, since the bracketed term must be nearly unity, can be rephrased as Nu/Re Pr = C/2 and constitutes Reynolds' analogy.