Pressure Drop Studies on Supercritical Helium Flowing in Horizontal Tubes

Abstract

Supercritical helium owing to its single-phase characteristics and enhanced heat transfer near the pseudo-critical region is envisaged as a potential coolant for superconducting magnets used in particle accelerators and fusion devices. However, near the transposed critical line, there is a wide fluctuation of thermophysical properties like specific heat at constant pressure, density, thermal conductivity, viscosity, etc. As a consequence of this fluctuation, heat transfer and fluid flow studies become difficult for accurate prediction of heat transfer coefficient and friction factor. In this paper, numerical simulation of supercritical helium flowing under turbulent conditions in a horizontal heated tube is performed using computational fluid dynamics (CFD) software ANSYS FLUENT v12.0.16. It is found that results of pressure drop obtained from simulation closely match experimental data in case of fluctuation free regimes. The friction factor indicating the frictional pressure drop occurring in a horizontal tube can be matched to existing correlations within given accuracies for fluctuation regimes. A correlation for friction factor that yields better results than those in literature is proposed based on the simulation data obtained. The accurate determination of the overall pressure drop in the tubes along with the optimum flow rates gives the estimation of pumping power required for enhanced heat transfer with flow of supercritical helium.