Experimental study on direct contact condensation of stable steam jet in water flow in a vertical pipe

摘要

Direct contact condensation is widely used in industrial applications due to its highly efficient heat and mass transfer. Many experimental and theoretical works have been performed on steam jet condensation in stagnant water in pool. However, the condensation of steam jet in water flow in pipes is not yet fully understood. Here, experiments are performed to study the direct contact condensation of stable steam jet in water flow in a vertical pipe. By using high speed camera and mobile thermocouple probe, we investigate condensation characteristics including the plume shape, plume length, temperature distribution, average heat transfer coefficient, and average Nusselt number. Five different plume shapes (hemispherical, conical, ellipsoidal, cylinder, and divergent) are identified visually, and their distribution is described in a three-dimensional condensation regime diagram based on steam mass flux, water temperature, and Reynolds number of water flow. The dimensionless plume length and average heat transfer coefficient are found to be within the range of 0.29-4.64 and 0.34-11.36 MW/m~2 K, respectively. Besides, empirical correlations are obtained for the dimensionless plume length, average heat transfer coefficient, and average Nusselt number as a function of three dimensionless parameters, i.e., dimensionless steam mass flux, condensation driving potential, and Reynolds number of water flow. The dimensionless radial temperature decreases exponentially from the center to the pipe wall and shows good self-similarity.