Forced convection saturated R134a boiling experiments were conducted in a vertical mini quartz tube coated with a transparent heater, the inner diameter of the tube was 1.33 mm and the heated length 235.5 mm. The dynamic of the saturated boiling process, and bubble characteristics and behavior were studied using a high speed CCD camera at different mass fluxes in up flow at 6.425 bar. The heat fluxes were 5 and 20 kW/m~(2). The flow visualization results show that the bubble departure frequency generally increases as the heat flux increases. In addition, bubble lift-off diameter, bubble growth rate and bubble velocity after bubble lift-off were determined by analyzing the images.
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