Direct contact condensation of steam jet in crossflow of water in a vertical pipe. Experimental investigation on condensation regime diagram and jet penetration length

摘要

The direct contact condensation of jets in fluid has been of great importance in many industrial applications. Experiments on condensing jets in initially stagnant fluid in pool have increased significantly in sophistication over the last few decades. For condensing jets in crossflow, however, the flow and geometry characteristics of the jet might be fundamentally different due to the complex convection effect induced by the crossflow. Here, experiments are performed to investigate direct contact condensation of steam jet in crossflow of water in a vertical pipe. The condensation regime diagram and jet penetration length are investigated visually by using high-speed camera and image processing methods. The condensation regime diagram mainly contains three kinds of condensation regime, i.e., chugging, condensation oscillation and stable condensation (i.e., stable conical shape, stable cylinder shape and stable expansion shape). The condensation regime is not only affected by steam mass flux and water temperature, but also affected significantly by Reynolds number of water flow. Therefore, condensation regime diagrams for different Reynolds number of water flow are developed. Both the regions of the chugging and condensation oscillation regimes expand slightly towards higher steam mass flux as Reynolds number of water flow increases. The dimensionless jet penetration length from experimental results is found to be in the range of 0.78-6.84. It increases with increase of steam mass flux and water temperature, but decreases with increase of Reynolds number of water flow. Empirical correlation is proposed for predicting the dimensionless jet penetration length depending on three dimensionless parameters, i.e., dimensionless steam mass flux, condensation driving potential and Reynolds number of water flow. The predicted results agree well with experiments and the discrepancies are within ±20%.