Pressure loss/gain boundary of gas-liquid downward flow in inclined and vertical pipes

Gas-liquid downward flow is frequently encountered in hilly-terrain pipelin es, down-comer pipes extending from offshore production platforms to sea fl oors, and steam injection wells in thermal enhanced recovery operations. Si nce the gravitational and frictional terms in the total pressure gradient e quation Sor downward flow have opposite signs, gas-liquid downward flow in inclined and vertical pipes may experience either pressure loss or pressure gain, depending on flow rates, pipe geometry, and fluid properties. A mech anistic model for the pressure loss/gain boundary of gas-liquid downward fl ow in inclined and vertical pipes is developed iii this work and is verifie d with available experimental results. The effects of pipe inclination angl e, inside diameter wall roughness, and fluid physical properties on the pre ssure loss/gain boundary are presented. [S0195-0738(00)00302-2].