Pressure drop of slush nitrogen flow in converging-diverging pipes and corrugated pipes

► Pressure-drop reduction appeared at velocities of over 1.5-2 m/s for both pipes. ► Solid particles were visualized using the PIV to study the reduction mechanism. ► Reduction of C-D Pipe is due to momentum exchange between solid and liquid. ► Reduction of corrugated pipe increases with increased solid weight fraction. ► Pipe friction factor for corrugated pipe is constant regardless of Re number.