Numerical simulation for design of probe to measure hydrogen thermal conductivity at high pressure by the transient short-wire method

Hydrogen energy is expected to be a next generation clean energy. However there are still many issues that must be overcome before commercializing hydrogen energy. Clarifying the mechanism for the effects of hydrogen on all types of materials and understanding the characteristics of hydrogen at high temperature and high pressure are indispensable. This study focuses on the development of the measurement technique for the thermal conductivity of hydrogen in the high pressure and the high temperature region. Numerical simulations are performed to investigate the effect of wire diameter, length and vessel size in a short-wire thermal conductivity probe designed for the study of hydrogen gas in the range of pressures from 0.1 to 100 MPa and temperatures from 25 to 500°C. The two-dimensional unsteady heat conduction equation is discretized using the finite volume method to calculate the thermal field. The influence of the natural convection was examined using an empirical equation from the literature. The size of the vessel, the wire diameter, and the wire length respectively were changed within the range of R=2.5-50mm, d=5-50μm, and H=20-160mm.