Experimental Study On Bubble Behavior In Subcooled Boiling Flow In Rectangular Channel

The bubble behavior of growth, sliding, springing, coalescence and departure in narrowrectangular channel under forced circulation at atmospheric pressure were investigated with ahigh-speed camera. The bubble behaviors under different thermal conditions were alsocomopared and analysed. A bubble force model under incline condition was established andverified by experimental results.The research work was a visualization experiment of bubble behavior of forcedcirculation with deionized water as the working fluid in a rectangular channel. Theexperimental phenomena recorded by using a high-speed camera at rates of5000frames/s.The range of experimental parameters: pressure:0.1MPa, mass velocity;347.2,520.8,694.4,868.1kg/m~2s, inlet subcooling:20℃,30℃,40℃, tilt angle:-20°,-10°,0°,10°,20°, heatflux:0~542.77kW/m~2.Many bubble behaviors were found during the experiment by using high-speed videocamera visualization investigation, such as the growing, sliding, departure, springing,springing and re-attaching,coalescence, two phase interface capillary fluctuation, collapsingof bubbles. The phenomenon has been described in the paper, The principle and related lawshas been analyzed and summarized by using the knowledge of bubble dynamics, fluctuationtheoretics and flow instability. The effect of the characteristic of flow field and temperaturefield of the rectangular narrow channel on bubbles’ sliding, springing and coalescence hasbeen investigated. The effect of thermal condition on bubble behavior and sliding heatexchanger has been compared and analysed. The data of bubble behavior of different inletsubcooling and heat flux on the same nucleation point has been measured and processed, suchas the average of the frequency of bubble production, the life time and diameter of bubble,theslidding bubble heat exchange ratio,it is found that with the wall heat flux increased, and thelifetime of the bubble, the bubble departure diameter increased gradually, sliding heatexchange decreased and the sliding distance increased；when the inlet subcooling of testsection decreased, The lifetime of the bubble and the bubble departure diameter increasedgradually, sliding heat exchange decreased while the sliding distance increased. The mathematical model of bubble behavior in tilted conditions has been established forinvestigating the effect of test section angle on bubble behavior, some conclusions were get asfollows:; when the tilt angle was negative, the buoyancy of the bubbles promoted bubble flowto the downstream and prevented the lift off of the bubble. The bubble sliding and the bubbleheat transfer with the wall got strengthen; When the angle was positive, the buoyancy ofbubble inhibited bubble sliding, image processing experiments verify the above conclusions.In addition, it was also found that the bubble frequency and diameter were increased graduallyas the inclination of test section increased positive.