A New Method for Cryogenic Fluid Thermal Conductivity Measurements and Thermophysical and Transport Properties of Hydrogen-Helium Mixtures

Abstract

New high field, high temperature superconducting magnets for fusion applications can operate at temperatures up to 65 K, well above those of low temperature superconducting magnets. These higher temperatures allow for the consideration of hydrogen as a magnet coolant, either pure or as a mixture with helium. However there does not exist experimental data on the thermophysical and transport properties of supercritical hydrogen-helium mixtures in the 15-70 K temperature regime and theoretical work is limited. Measurement of transport properties of cryogenic fluids is diffucult due to issues related to natural convection. This thesis presents a new method, known as the confined 3ω method for fluids, which measures the thermal conductivity and diffusivity simultaneously of cryogenic fluids. This method is then combined with measurements of density and viscosity to measure the thermophysical and transport properties of hydrogen-helium mixtures from 20- 100 K.