Numerical Simulations of Cryogenic Hydrogen Cooling in Vortex Tubes with Smooth Transitions

Abstract

Improving efficiency of hydrogen cooling in cryogenic conditions is important for the wider applications of hydrogen energy systems. The approach investigated in this study is based on a Ranque-Hilsch vortex tube (RHVT) that generates temperature separation in a working fluid. The simplicity of RHVT is also a valuable characteristic for cryogenic systems. In the present work, novel shapes of RHVT are computationally investigated with the goal to raise efficiency of the cooling process. Specifically, a smooth transition is arranged between a vortex chamber, where compressed gas is injected, and the main tube with two exit ports at the tube ends. Flow simulations have been carried out using STAR-CCM+ software with the real-gas Redlich-Kwong model for hydrogen at temperatures near 70 K. It is determined that a vortex tube with a smooth transition of moderate size manifests about 7% improvement of the cooling efficiency when compared vortex tubes that use traditional vortex chambers with stepped transitions and a no-chamber setup with direct gas injection.

Determination of Rate Coefficient for Para-Orthohydrogen Conversion in Cryogenic Vortex Tube

“…However, in the present analysis, the vortex tube primary role is to serve as a vortical reactor for assisting para-orthohydrogen conversion accompanied by significant cryogenic cooling while not involving moving parts. The present study is a continuation of previous efforts aimed at developing this technology [4,5]. The main goals of the current investigation are to set up a computational fluid dynamics ENFHT 135-2 (CFD) simulation of a hydrogen vortex tube, to validate this modelling against experimental data, and to determine the effective rate coefficient for para-orthohydrogen conversion in vortex tubes.…”