S-ST-1-6 Heat Transfer Correlations in the Transition Range - Summary Report of Methods Recommended for Tubeside Calculations

J. W. Palen and J. Taborek

Presently available heat transfer correlations for the transition region are not compatible at the region boundaries with recommended correlations for both the laminar and turbulent regions. Furthermore, they are all based on too limited data samples to adequately predict the varying effects of Reynolds number, tube length-to-diameter ratio, and diminishing effects of natural convection in the transition region.

Based on 172 data points for 11 fluids including water, alcohols, and hydrocarbons, a new transition region correlation was developed to provide more accurate prediction which would blend smoothly into present HTRI correlations for the laminar and turbulent regions.

In the course of this development, the range of validity of the laminar heat transfer correlation (Report 4) had to be extended to include less viscous fluids, (both liquids and gases) with Prandtl numbers as low as 0.5.

The transition correlation involves a linear proration of laminar and turbulent correlations calculated at the regime boundaries. Accuracy of prediction over a wide range of conditions was very good, considering the unstable nature of this flow regime, and was, in fact, comparable to the levels of accuracy expected for the laminar and turbulent equations.