Numerical Analysis of Heat Transfer Deterioration of Hydrogen Flowing in a Circular Pipe under Transcritical Boundary Conditions.

In various systems, such as rocket engines, efficiency is improved by increasing the pressure so that these systems operate at extremely high supercritical pressures. At this pressure, pseudo-boiling occurs, and heat transfer deteriorates, suddenly decreasing when certain temperature limits are exceeded. This study numerically solved the Navier-Stokes equations for a circular cooling channel. In addition, supercritical hydrogen was used as a coolant. The thermophysical and transport properties were defined as a user-defined function in ANSYS FLUENT. The results showed that increasing the operating pressure significantly reduced the heat transfer deterioration, improved the cooling capabilities, and minimized pressure drops. Increasing the mass flow rate enhances the heat transfer but increases the pressure losses. The influence of the operating pressure and the mass flow rate on the deterioration of the heat transfer was investigated in detail. [ABSTRACT FROM AUTHOR]