The fundamental two-phase flow characteristics of slush nitrogen in a pipe are numerically and experimentally investigated to develop effective cooling performance for long distance superconducting cables. First, the governing equations of the two-phase slush nitrogen flow based on the unsteady thermal nonequilibrium two-fluid model are presented and several flow characteristics are numerically calculated taking into account the effects of slush volume fraction, particle diameter, and duct shape. Furthermore, in experimental study, minute slush is generated by the slush atomization nozzle and the unsteady pressure and temperature distributions of two-phase slush nitrogen flow along the longitudinal direction of pipe are measured. According to the numerical and experimental results, it is found that the reduction of the pressure loss by using slush is possible in the case of long distance pipe lengths. Also, optimized thermal flow conditions for cryogenic two-phase slush nitrogen with practical use of latent heat of slush melting are predicted for the development of new type superconducting cooling systems.