An experimental comparative study on condensing supersonic steam jets in water tank: Square, rectangular, and circular cross-sectional shapes

The direct contact condensation phenomenon has gained significant attraction among researchers due to positive aspects such as low driving potential and rapid heat transfer rates in its industrial uses. The present study explores the effect of the cross-sectional shape of converging-diverging on steam-submerged jet condensation behavior. The influence of three cross-sections (circular, square, and rectangular) on steam jet shapes, jet length, average heat transfer coefficient, and maximum expansion ratio were studied. The dimensionless steam jet length for circular, square, and rectangular nozzles has been found in the range of 2.2-7.7, 2.43-8.41, and 2.22-8.35, respectively. The maximum expansion ratio for circular, square, rectangular major axis plane, and rectangular minor axis plane has been found in the range of 1-1.71, 1.14-2.15, 1.22-2.82, and 1.06-1.45. Results show that the maximum expansion ratio and dimensionless jet length rise with steam pressure and water temperature rise. Dimensionless jet length decreases in the order of nozzle with cross-section: square > rectangular > circular. Correlation for dimensional jet length of both circular and non-circular nozzles is presented using the analytical and curve fitting methods. The maximum expansion ratio decreases in order: major axis plane > square > circular > minor axis plane. The average heat transfer coefficient (MW/m(2 o)C) for circular, square, and rectangular nozzles has been found in the range of 1.16-4.88, 0.89-3.14, and 1.01-3.49. Results show that the average heat transfer coefficient falls with the rise in steam pressure and water temperature. The average heat transfer coefficient decreases in order: circular > rectangular > square. Condensation regime maps are proposed for circular, square, and rectangular nozzles, including diagonal plane effects in square and rectangular nozzle.