The condensation behavior and heat transfer characteristics of steam bubbles with air were investigated by visual experiments

with steam mass fraction between 0.5 and 0.8. Bubbles of gas mixture were injected into cool water at two different temperatures through nozzles of diameter 1.5 and 3 mm. The condensing processes of bubbles were recorded by high speed camera and the thermodynamic parameters of bubbles were obtained by the variation of bubble volumes

from which the condensing heat transfer coefficients were calculated. The results show that the bubble deforms continuously when it condenses and a hollow forms in the middle of the bubble at the beginning of the condensing process. The condensing heat transfer coefficient decreases as cool water temperature decreases and bubble volume increases

while it is not affected by the nozzle diameter. The condensing heat transfer is deteriorated by the noncondensing gas. A correlation to predict the heat transfer coefficients is established using all the 65 data obtained in this experiment.