S-ST-1-3 Non-Isothermal Pressure Drop in Laminar and Transitional Flow of Liquids Inside of Tubes

A. Yarden, J. W. Palen, and J. Taborek

For heating or cooling, the isothermal velocity profile is distorted on account of two phenomena: a) the viscosity gradient which develops between the wall and the liquid bulk, and, b) the natural convection currents which result from a corresponding density gradient.

For our investigation 450 data points from 3 different sources were used. Most of the data were proprietary to HTRI and covered a considerably wider range of parameters than was available to past researchers.

Three presently existing methods were evaluated: a) the film temperature method of McAdams, b) the viscosity gradient method of Sieder-Tate, and c) the semi-theoretical method of Yamagata. As a general rule, all the methods predicted within ± 30% a majority of the data on which they were based originally, but failed more or less badly when tested against our large data set of extreme parameters.

A new method of correcting for the non-isothermal effects is proposed. It is based on the viscosity ratio principle, and includes a correction factor for the natural convection effects.