A comparative study of thermal design correlations for turbulent flow in helical-enhanced tubes

A number of investigators hale carried out studies on enhanced tribes, lead ing to better understanding of their thermal hydraulic characteristics. The variables considered in these investigations include the "design" paramete rs namely, height, pitch, and helix angle of the rib, and the tribe diamete r, and "flow" variables such as the Reynolds number and the Prandtl number. The pressure drop and heat transfer correlations needed for prediction of the performance of ribbed tribes can be developed using either an analogy a pproach or an empirical technique. These two methods are explained, along w ith the many correlations that have been developed based on them. The numer ous studies pose a dilemma for the designer in selecting the most appropria te correlation. This article outlines the various correlations that are ava ilable for predicting the thermal-hydraulic performance of turbulent flows in enhanced tribes. Specific correlations that are valid for particular enh ancement types as well as general correlations are presented. The correlati ons are applied to a comprehensive database and the predictions are analyze d. A parametric analysis carried out using the different correlations indic ates the relative influence of enhancement design parameters OH friction fa ctor and heat transfer In particular, the design variables affect the heat transfer/friction factor characteristics differently for various tribe type s.