Sensitivity studies on the hydrogen filling station with comparison 1D / 3D models, different configurations or exploration of other phenomena. These studies have been carried out by BE CFD team at Extia Don't hesitate if you have any questions to contact us at cfd@extia.fr

1. Hygrogen filling station
1

2. A hydrogen station is a storage or filling station for hydrogen. The hydrogen is dispensed by weight. There are two
filling pressures in common use. H70 or 700 bar, and the older standard H35 or 350 bar.
A Hydrogen Refuelling Station (HRS) refills an electric vehicle fuel cell with pressurized hydrogen. A simple HRS
consists of hydrogen storage tanks, hydrogen gas compressors, a pre-cooling system, and a hydrogen dispenser,
which dispenses hydrogen to pressures of 350 or 700 bars depending on the type of vehicle. A typical hydrogen
car will be refuelled in three minutes and a bus in seven minutes.
PRHYDE is a European based project looking at the current and future developments needed for refuelling
medium and heavy-duty hydrogen vehicles, predominantly road vehicles, but also for other applications such as
rail and maritime.
GENERAL PRESENTATION

3. METHODOLOGY
INPUT DATA
Hydrogen tank
Liner (5mm)
Composite (15mm)
195,1 mm
radius = 10,8 mm
References for correlation :
• Protocol for heavy duty hydrogen refueling: a modeling benchmark
In this publication, the initial purpose is to compare different softwares to calculate the refueling system.
• Phryde documents https://prhyde.eu/
Internal diameter of 300mm with a length of 1246mm to obtain the volume of 350L.
A heat coefficient is considered equal at 15 W/m²/K with external temperature of 15°C.
Initial temperature is 15°C for an absolute pressure of 60 bar.
T = 10min to fill the tank.
The behavior of hydrogen is complex, its physical properties are set as function of temperature and pressure. The modeling of these
properties is one of the main difficulty of this study.
Single Vessel Characteristics
Type III Single Vessel (Large)
H35

4. METHODOLOGY
MODELLING HYPOTHESIS
4
𝑑𝑚𝑔
𝑑𝑡
= 𝐶 𝑘𝑣𝑃𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟
ρ𝑁
𝑇𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟
𝑑𝑚𝑔
𝑑𝑡
= 2 𝐶 𝑘𝑣
ρ𝑁 (𝑃𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟 − 𝑃𝑡𝑎𝑛𝑘)𝑃𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟
𝑇𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟
𝑃𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟 > 2 𝑃𝑡𝑎𝑛𝑘
𝑃𝑑𝑖𝑠𝑝𝑒𝑛𝑠𝑒𝑟 ≤ 2 𝑃𝑡𝑎𝑛𝑘
𝐶 : Constant = 257
ρ𝑁
Temperature (K)
𝑇
Pressure (bar)
𝑃
𝑑𝑚𝑔
𝑑𝑡
Mass flow
The equation of inlet mass flow in the tank has been introduced in FLUENT 2021 to calculate the setup in function of mass flow coefficient kv
(m3/h). The formula, which has been implanted, is air liquid formula defined in Phryde document.
Gas density in
normal conditions
(0.08988 kg/m3)

5. 5
Results and litterature comparison
The nodal model gives the same final pressure at the end of calculation, but the final hydrogen temperature is different. The temperature gap between CFD
model and nodal model is 7°C on the mean temperature.
This difference could be explained by :
• The importance of the tank shape and the 3D geometry in general
• The difference of internal heat coefficient. The exchanges are considered averaged on the internal wall of the tank. As it can be seen below, the
temperature gap between the average and maximum temperature is 47°C for the composite and 29°C for the liner. Moreover, the inertia of nodal model is
equally averaged. The impact of the jet caused by the nozzle is smoothed with the nodal model.
The composite temperature is very important because this material has critical temperatures that should not be exceeded. This material is complex, it amounts
of a multiple-layered assembly, implying the thermal conductivity to be orthotropic. This phenomena is hardly modeled with the nodal model.
Graphe extract from publication Simulation

6. 6
Temperature on symmetry plane (°C)
It is interesting to see the different behaviors between the two different nozzles. The big diameter presents a thermal stratification and
could therefore cause different problems for the filling and the damage of materials.
Velocity on symmetry plane (m/s)
Study of two nozzle diameters for this geometry

7. Goal : Study the impact of external temperature on the hydrogen behaviour during the transition inside the pipe
10 m
DN20 external diameter
Inlet :
hydrogen
Mass flow : curve from tank model
Temperature after the precooling = -15°C
External wall:
Steel
Ambient temperature = 15°C
Heat coefficient= 5 W/m²/K
Curve of mass flow from the tank model
Velocity and temperature development over time on
the plane after 9,5m
Velocity and temperature development over time on
the plane after 9,5m
(focus between -10 and -15°C)
-14,4°C
100s The initial pipe temperature has a massive
influence on the delay to reach the operating
temperature at the tank inlet.
Moreover, the inlet temperature is impacted by
the tank length. The hydrogen enters the tank
at -14,4°C instead of 15°C.
Study of pipe before the tank

8. 8
Velocity and temperature development over time on the plane after 9,5m
(focus between -10 and -15°C)
14,4°C
100s
Velocity and temperature development over time on the plane after 9,5m
This part is going to be coded with a UDF file to integrate the phenomena directly in fluent.
Study of pipe before the tank

9. 9
Modelica model
Tinit = 15°C
Pinit = 100 bar
Curve of hydrogen massflow enters in
tank
Text = 15°C and external heat coefficient
of 10 W/m²/K
Tinlet = -15°C
Fluent Model
With Coolprop library
It is possible to pre-design the whole process line with the Modelica model. It is also
possible to do a weak coupling between CFD and the nodal model.
Coupling system modeling / CFD

10. 10
Example of other studies on this subject
Sorbent
Design optimization for
radioactive zeolite waste
storage
Based on this publication
Characterization and storage of radioactive
zeolite waste - Isao Yamagishi
Multiple tanks
Different tank shapes Skid
Hydrogen