Two-phase flow resistance in flexible metal hoses

This study presents the two-phase flow resistance, hence the friction factor and the pressure drop for air–water mixture flowing in flexible metal hoses. Experiments were performed under the following conditions of two-phase parameters; mass flux from 200 to 1150 kg/m2 s, gas quality from 1 to 60% and system pressure from 3 to 10 bar. The inner diameters of the tested hoses were 25, 40, 50 and 65 mm with a ratio of ridge depth to inner diameter (r/d) from 0.02 to 0.1 and a ratio of pitch to inner diameter (p/d) from 0.06 to 0.3. The results demonstrate that the two-phase flow resistance, energy dissipation and friction losses in flexible metal hoses are perceptible greater than that in pipes. Therefore, the two-phase pressure drops of the hoses are two to five times greater than that in smooth pipes. The two-phase friction factor of such hoses increased from 0.035 up to 0.2 in dependence on the influencing flow and geometrical parameters. Based on the energy balance and the presented experimental results, a new model has been developed to calculate the two-phase pressure drops and hence the friction factor of flexible metal hoses. The model includes the relevant primary parameters, fit the data well and is sufficiently accurate for engineering purposes. The results reported enable practical designs with standard products and optimization of the hose geometry for specific conditions.