Pressure-drop reduction and heat-transfer deterioration of slush nitrogen in triangular pipe flow.

Slush fluids are solid-liquid two-phase fluids in which a cryogenic liquid contains solid particles of the same substance as the liquid. Due to the high-density and latent heat of fusion of the solid particles, they possess superior properties as functional thermal fluids. Slush hydrogen can be efficiently transported and stored, and can also be employed as the refrigerant for high-temperature superconducting equipment using MgB2. Here, pressure drop reduction and heat transfer deterioration experiments were performed on slush nitrogen flowing in a horizontal equilateral triangular pipe having sides of 20 mm each, with flow velocity of 0.6~4.0 m/s, solid fraction of 0~22 wt.%, and heat fluxes of 0, 10, and 20 kW/m2. Pressure drop reduction became apparent at flow velocities above 1.6~1.8 m/s, representing a maximum amount of reduction of 16~18% when compared to liquid nitrogen, regardless of heating. Heat transfer deterioration was seen at flow velocities above 1.6~1.8 m/s, for a maximum amount of 14~15%.