Bubble dynamics during degassing of liquids at microgravity conditions

This work investigates the growth of bubbles generated in a liquid saturated with dissolved CO2 when its temperature is rapidly and locally raised above the saturation value, still below the boiling point of the test liquid. Three test liquids with different physical and transport properties were studied: water, glycerine/water mixture 42158 w/w, and n-heptane. Bubbles grow at the tip of a roughly spherical miniature heater (thermistor), whose temperature varies linearly with the power of an applied heat pulse. Nucleation and growth of single bubbles is studied, triggered either by continuous heat pulses or by intermittent heat pulses. A one-dimensional spherically symmetric bubble growth model based on heat and mass transfer on the liquid side is employed to extract the average bubble temperature evolution curves from the experimental bubble growth curves. Comparisons between extracted average bubble temperature evolution data and measured thermistor temperatures reveal features of the heat-triggered bubble growth. (c) 2006 American Institute of Chemical Engineers.