The Influence Of Noncondensable Gases On Condensation Inside Tubes: An Experimental Analysis

The Department of “Ingegneria Nucleare e Conversioni di Energia ” of the University of Rome “La Sapienza” has been carried out an experimental campaign to analyse the in-tube steam condensation heat transfer, in the presence of high percentage of noncondensables at atmospheric pressure. Vapour-air mixture condensation tests were performed for different tube inclinations, steam mass flow rates, power level and noncondensable concentration in the mixture. Noncondensable gases mixed with steam strongly affect condensation heat transfer coefficient. Tests carried out during the experimental campaign showed that condensation heat transfer coefficient decreases to 50% of the original value when mixture air percentage varies from 0% to 2%, while with a percentage of air of 10% the condensation heat transfer coefficient is reduced to 10% of the condensation heat transfer coefficient with pure steam. A reduction of another order of magnitude (leading to 1% of the pure steam condensation coefficient) is attained with air concentration of some 50%. In the paper, the main results obtained in the experimental campaign and the analysis performed are presented and discussed.