Countercurrent gas–liquid flow in inclined and vertical ducts — I: Flow patterns, pressure drop characteristics and flooding

An experimental investigation into adiabatic gas–liquid counterflow in inclined and vertical rectangular ducts with a square-edged gas inlet is conducted. Water, methanol, propanol, air, argon, helium and hydrogen are used as working fluids. The duct height and width are varied from 50 to 150 mm and 10 to 20 mm respectively. At low gas flow rates the two-phase pressure gradient is gas Reynolds number related while it becomes dependent on the densimetric gas Froude number as the gas flow is increased. The hydraulic diameter is the length dimension required for the gas Reynolds number, while the duct height becomes the characteristic dimension in the Froude number. The flooding gas velocity is found to be strongly dependent on the duct height, the phase densities and duct inclination.