Fundamental study of pipe flow and heat transfer characteristics of slush nitrogen

This study deals with the pipe flow and heat transfer characteristics of slush nitrogen. Slush nitrogen is a mixture of liquid and solid nitrogen in which fine solid particles are dispersed in the liquid phase. The latent heat of fusion can be utilized to increase the refrigeration supply. Therefore, it is expected that it will be applied as a high-performance refrigerant for high-temperature superconducting devices. The pipe flow and heat transfer characteristics were investigated experimentally by taking the flow velocity and the mass fraction of solid as control parameters. From the results of this study, it was clarified that both the pipe friction coefficient, lambda, and the Nusselt number, Nu, of slush nitrogen were larger than those of ordinary single-phase fluid in the low Reynolds number region. However, those non-dimensional characteristic numbers, lambda and Nu were found to gradually approach those of a single-phase fluid as the Reynolds number increases.