S-ST-1-4 Heat Transfer to Liquids in Laminar Flow Inside of Tubes

J. W. Palen and J. Taborek

Classical theoretical solutions for laminar heat transfer in horizontal tubes completely fail to predict actual data, due to the inability to account for physical property variations between the tube wall temperature and the fluid bulk temperature.

Ten presently available empirical laminar heat transfer correlations were tested against over 600 horizontal tube data points (over 400 unpublished) on hydrocarbon oils. These ranged in Prandtl number from 15 to 19,000, in Grashof number from 0.5 to 27,000,000, and in bulk-to-wall viscosity ratio from 0.001 to 55. All correlations gave poor predictions in one or more ranges of the data set.

An improved horizontal tube correlation was developed, which gives superior prediction over the entire data set; and, in addition, extrapolates in extreme cases to forms compatible with theory.

A vertical tube correlation of the same form is also presented. This equation must be considered tentative, however, due to the small amount of vertical tube data. It was developed using the complex Pigford theoretical equations, and is expected to give equivalent results in a simpler equation form.

The correlation can be represented by the familiar j-factor plot, on which a reasonable interpolation through the transition region can be estimated. (See subsequent Report 5.)

The report also includes a survey of all important theoretical and empirical laminar intube heat transfer work, spanning nearly a century, from the time of Graetz to the present.