FRICTION FACTORS AND HEAT TRANSFER COEFFICIENTS FOR HYDROGEN SYSTEMS OPERATING AT SUPERCRITICAL PRESSURES

Predicting heat transfer coefficients and friction factors for hydrogen systems operating near and above the thermodynamic critical pressure is at best difficult. Yet most hydrogen land-based and aerospace systems of significant power density operate within this regime. In this paper we discuss a modification of the Patankar-Spalding method to include density fluctuations in predicting heat and mass transfer. The essence of this method is then empirically expressed in terms of the volumetric expansion coefficient, the wall to bulk temperature difference, and the reduced Nusselt number. The expression is then applied to hydrogen data. The method is meant to facilitate preliminary design, but for detailed analyses the numerical code is recommended.