An indirect expansion technique was proposed to measure the gas holdup in a non-transparent bubble column with 0.1 m inner diameter and height of 5.2 m.Air and distilled water were employed as gas and liquid phases

respectively.The experimental results show that the average and maximum errors of gas holdup are less than 2% and 4.5%

respectively

between the indirect expansion and pressure drop methods at atmospheric or elevated pressure.Moreover

the gas holdup increases with operating pressure when the superficial gas velocity is a constant

while the effect of static liquid height on gas holdup can be ignored when the operating pressure and superficial gas velocity are fixed.