Experimental Evaluation of Fluid-to-Fluid Scaling Models for Deteriorated Heat Transfer at Supercritical Pressures

Abstract

Experimental evaluations of two fluid-to-fluid scaling methods for deteriorated heat transfer (DHT) in upward vertical flows in tubes at supercritical pressures were performed at the University of Ottawa Supercritical Heat Transfer Loop (SCUOL), using Refrigerant R134a as a medium at conditions that were determined by scaling those in previous carbon dioxide tests in the same loop. Two scaling methods were considered: the Ottawa method, which was based on local scaling, and the Pisa method, which was based on global scaling. Both methods were partially successful in scaling the occurrence or absence of DHT, but only when allowing for the thresholds of DHT onset conditions to span some ranges rather than being sharply defined. Both methods were inaccurate in predicting the exact location of DHT and the value of the heat transfer coefficient.