Experimental study of in-tube steam condensation in presence of high percentage of noncondensables, aimed at the design of an inherently safe heat transfer emergency system

The Department of “Ingegneria Nucleare e Conversioni di Energia ” of the University of Rome “La Sapienza”, in cooperation with the Department of “Fisica Tecnica” of the same University, designed and preliminary tested an experimental apparatus for the analysis of heat transfer coefficient with in-tube condensation of steam, in presence of high percentage of noncondensables at atmospheric pressure. The aim of the experimental activity is the design of an innovative emergency heat removal system for nuclear and process industry; this system has to be characterised by high reliability: its operation is based on the use of natural circulation of fluids and non-energised, passive, components. The main results of the experimental analysis are: 1) The condensation heat transfer coefficient is strongly affected by noncondensible gases, with a one order of magnitude decrease with an inlet mass percentage of air of 2%, and of two-order of magnitude decrease for an inlet percentage of 60%. 2) The inclination of the tube does not affect the condensation heat transfer for gas percentage higher than 5%.