Session: 01-03: Modeling and Simulation

Paper Number: 139421

139421 - Extension of the Flow Calculation in ISO 6358 by Real Gas Behavior to Enhance Accuracy of Hydrogen Simulations 

Abstract: 

The flow resistance of pneumatic valves and restrictors is usually experimentally characterized and modeled by means of the equations and test setups provided in ISO 6358. The equations fulfill the requirements with sufficient accuracy when the gas properties and investigated parameters allow for an ideal gas assumption, as is the case for conventional pneumatics.

 

The development of hydrogen storage systems and filling stations requires modelling of complex hydrogen networks at pressures of up to 100 MPa. Under these conditions, ideal gas assumptions are no longer valid, and the flow behavior of technical resistances is only roughly approximated by means of ISO 6358. Several papers cover the effect of real gas behavior on the mass flow through critical nozzles and formulate relations between the inflow conditions, real gas equations and the conductance of the nozzles. The fundamentals therefore are also included in IEC 60534-2-1. To date, the effect on subcritical flow has not been studied in detail. Moreover, the before mentioned studies mainly rely on real gas models with limited accuracy and range of validity.

 

This paper therefore presents an easy-to-implement approach for modeling the flow through ideal nozzles using tabulated thermodynamic values. It covers the entire flow regime and allows unrestricted application for all gaseous media and operating points if the tabulated values cover all externally and internally occurring values of the state variables. This new approach is first validated using ISO 6358 with tabulated values for an ideal gas. A subsequent selective validation is carried out with measurement and CFD simulation results for hydrogen from various literature sources and tabulated values from the N.I.S.T. database. Finally, the effects of the real gas behavior on the flow rate and gas temperature are discussed in detail, highlighting additional challenges in valve design resulting from the real gas behavior and emphasizing the need to implement such models.

Presenting Author: Olivier Reinertz RWTH Aachen University, Institute For Fluid Power Drives and Systems (ifas)

Presenting Author Biography: Olivier Reinertz received his diploma and his doctoral degree in mechanical engineering from RWTH Aachen University, Germany. He is currently Scientific Director at the Institute for Fluid Power Drives and Systems (ifas) at RWTH Aachen University. His research focuses on the model-based analysis of fluid power components and systems and the derivation and validation of innovative strategies for efficiency and performance optimization with an emphasis on compressed air and gas-powered systems.

Authors:

Olivier Reinertz RWTH Aachen University, Institute For Fluid Power Drives and Systems (ifas)
Katharina Schmitz RWTH Aachen University, Institute for Fluid Power Drives and Systems (ifas)