4th International Conference on Hydrogen Safety

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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
ICHS2011-109
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
Gesi Liu, Yongzhi Zhao, Yanlei Liu, Jinyang
Zheng, Yuntang He
Institute of Process Equipment Zhejiang
University, Hangzhou, P. R. China September 12,
2011
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
Zhejiang University is located in Hangzhou which
is near Shanghai, P.R. China.
180km
1h train
Hangzhou(3015'9.44"N, 120 9'54.36"E) by Google
Earth
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
Hangzhou was honored as "the most beautiful and
magnificent city in the world" by the Italian
traveler Marco Polo.
The West Lake of Hangzhou has just been named as
a World heritage site in June 24, 2011.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
Zhejiang University was founded in 1897 as one of
the oldest institutions of higher learning in
China. It has always been ranked among the few
top universities in China. There are five
campuses Zhijiang, Xixi, Yuquan, Huajiachi and
Zijingang.
Xixi campus
Yuquan campus
Welcome to ZJU and Hangzhou
Zhijiang campus
Huajiachi campus
Zijingang campus
44,151 full-time students, including 24,983
undergraduates, 11,883 graduate students working
for master degree, 6,050 doctoral candidates,
1,235 foreign students. Total collection of
library 6,260,000 Volume.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
Introduction
1
Mathematic model
2
Contents
3
Results and discussion
4
Conclusions
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Hydrogen has been recognized as an ideal energy
carrier for stationary and mobile applications.
The industrialization of hydrogen economy needs
systems integration.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
In demands of 500 km driving range with one
charge for HFCV, 70 MPa gaseous hydrogen storage
system with high hydrogen storage density has
become one of the most developed solution. High
pressure gaseous hydrogen storage is normally
achieved by two kinds of on-board cylinders (type
3 and type 4), which are made of carbon fiber
reinforced polymer (CFRP) and certain liner
(metal liner for type 3 cylinder, non-metal one
for type 4).
HFCV
CFRP cylinder
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction

• For commercialization of HFCV, fast filling of
  on-board cylinder is necessary, which may lead to
  significant temperature rise within the cylinder.
  That may cause failure of cylinder and
  under-filling. So the maximum temperature within
  the cylinder is restricted below 85ºC by
  available standards and codes such as
• ISO/TS 15869 Gaseous hydrogen and hydrogen blends
  - Land Vehicle Fuel Tanks, International Standard
  Organization.
• SAE J 2601 Fueling Protocols for Light Duty
  Gaseous Hydrogen Surface Vehicles, Society of
  Automotive Engineers.
• To avoid risks caused by temperature rise, it is
  essential to conduct research on the mechanism
  and control methods of temperature rise.

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction

• Many investigators have done experiments,
  simulations and theoretical studies on issues of
  the fast filling
• Most of the researches on fast filling
  concentrate on the cases with the working
  pressure of 35 MPa, e.g. Monde et al. (2007), Liu
  et al. (2010), Dicken et al. (2007, 2008),
  Heitsch et al. (2011), Zhao et al. (2010), Kim et
  al. (2010), Hiroshi et al. (2006), Toshihiro et
  al. (2008), etc.
• Fast filling experiments of 70 MPa cylinder have
  been done by Hiroshi et al. (2006) and Khan et
  al. (2009).

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction

• The aforementioned researches shows that
• For 35MPa cases with type 3 cylinder, the problem
  of temperature rise is relatively small.
• However, normal filling procedure for type 4
  cylinder may lead to higher temperature rise than
  that of type 3.
• For 70MPa cases with both kinds of cylinders, the
  final maximum temperature with normal filling
  procedure may be unexpected high and intolerable
  at relatively high atmosphere temperature.

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Our group has been engaged in the rapid filling
of HFCV for several years. Experiments and
simulations on 35MPa HFCV storage system have
been done. The published results on fast filling
of HFCV cylinder include Liu et al. (2010)
investigated the thermal behaviors such as
temperature rise and distributions inside 35 MPa
(150 L, type 3) hydrogen storage cylinders during
its refueling by experiments. Zhao et al.
(2010) investigated the effects of different
average mass filling rates, initial pressure
within cylinder and ambient temperature on the
maximum temperature rise during refueling by
numerical simulation.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Experiment devices of 35MPa fast filling (150 L,
type 3 cylinder)
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Hydrogen refueling station (70MPa available)
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Our group is now engaging in the issues of 70MPa
HFCV storage system. This paper is a predicting
study for the experiments of 70MPa fast filling
process which has just been done few days ago.
And the test cylinder (74L, type 3) and
experiment devices are shown in the following
pictures
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Pre-cooling device
Online monitoring system
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
1. Introduction
Structure diagram of the test 70MPa HFCV cylinder
is shown below. The volume of the type 3 cylinder
is 74 L. The diameter of inlet pipe is 10 mm. The
simulated cylinder is treated as a combination of
two parts fiber layer and aluminum alloy liner.
aluminum alloy liner
fiber layer
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
2. Mathematic model

• 2.1 Assumptions
• A 2-dimensional axisymmetrical CFD model is
  presented, including A jet-modified standard k -
  ? model and a real gas model. Assumptions
  proposed for simplifying the model are described
  as follows
• Heat exchange coefficient of natural convection
  and the ambient temperature are considered as
  constant
• The model is based on 2-dimensional
  axisymmetrical algorithm, and buoyancy effect is
  neglected.
• Temperature of inlet gas is considered as
  constant, which is equal to ambient temperature.
• Initial temperature of the whole system is
  considered as the ambient temperature. And the
  initial pressure is stable at the very beginning
  of the filling process. The gas inlet is treated
  as pressure inlet.

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
2. Mathematic model
2.2 Equations
The mass conservation equation
The law of conservation of momentum yields the
equations below
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
2. Mathematic model
2.2 Equations
The turbulence kinetic energy k and its rate of
dissipation ? are obtained from the following
transport equations
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
2. Mathematic model
2.2 Equations

• As the varying range of the hydrogen properties
  during the fast filling is quite large, a real
  gas model must be adopted.
• The modified Benedict-Webb-Rubin equation of
  state has good accuracy
• In the region between 250 and 450 K and at
  pressures from 0.1 to 300 MPa, the uncertainty in
  density is 0.04. Speed of sound data are
  represented within 0.5 below 100 MPa. The
  estimated uncertainty for heat capacities is
  1.0.
• The uncertainty in thermal conductivity is
  estimated to 10 below 700 atm.
• The uncertainty in viscosity ranges from 4 to
  15.
• In this model, the modified Benedict-Webb-Rubin
  equation of state is applied for calculating the
  properties of hydrogen gas, and the detail can be
  found in Younglove and Mclinden (1994).

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
2. Mathematic model
2.3 Comparison with previous data
This model gives a good match of the previous 35
MPa experiment data of Liu et al (2010). For
instance, the mass average temperature rise of
gas vs. time curve is shown in left for the case,
which is initialized with 3 MPa and charged with
linear pressure-rise pattern. The simulation
results generally agree with the experiment data.
The deviation may be mainly caused by the
nonlinearity of experiment pressure-rise pattern,
while the pattern of simulation is exactly linear.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
2. Mathematic model
2.4 Inlet settings
For different cases, the inlet pressure-rise
patterns shown in left are set respectively. The
temperature of inlet gas for all cases is assumed
as the ambient temperature, and similarly initial
pressure is 2 MPa. The red group of cases is
analyzed for effects of different filling time
. The blue group is for effects of different
pressure-rise patterns.
Red group of different filling time
Blue group of different pressure-rise patterns
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
3. Results and discussion
3.1 Characteristics of temperature field
Temperature contour of the cylinder after 160
seconds for the case of 180s_p1
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
3. Results and discussion
3.1 Characteristics of temperature field

• For instance, temperature contour in previous
  page shows characteristics of temperature field.
  And there are similar characteristics for all
  cases
• There is significant temperature gradient in
  interlaminar area between the aluminum alloy
  liner and CFRP layer, which may caused by the low
  thermal conductivity of CFRP.
• The highest temperature of hydrogen gas usually
  appears in the near-wall space around far end
  enclosure.
• Because of jet effect, there is also remarkable
  temperature gradient along the jet path.
• The standard deviation of hydrogen gas
  temperature with cylinder (excluding the jet
  path) is relatively small, which shows good
  temperature homogeneity.

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
3. Results and discussion
3.2 Effects of different filling time
As shown in left, the curves show that the
maximum temperature rise decreases with the
increasing of filling time. That may be caused by
the discrepancy among different conditions of
heat dissipation. The discrepancy means that
the efficiency of cylinder heat dissipation is
related to pressure-rise rate.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
3. Results and discussion
3.2 Effects of different filling time
As shown in left, the mass flow rate of inlet
section rises rapidly to a certain limit in the
first few seconds. Then the rate is falling down
nonlinearly during the residual filling time,
which indicates the real gas effects of hydrogen
gas. And nonlinearity level of mass flow rate
curve increases with the decreasing of the
filling time.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
3. Results and discussion
3.2 Effects of different filling time
The state of charge (SOC) curve is shown in left,
which is described below Where ?end is the
final average density after the filling process
in the cylinder. ?0 is the density of 288 K at
the target pressure. The final SOC are 89.7 for
120s, 90.8 for 180s and 91.2 for 240s, which
decreases with filling time. The decreasing trend
affirms the potential risks of cylinder
underfilling.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
3. Results and discussion
3.3 Effects of different pressure-rise patterns
The maximum gas temperature curve shown in the
left has similar results with the experiment
results found in Hirotani et al. (2006), which
shows small difference of final maximum gas
temperature among all cases. The difference means
that the efficiency of cylinder heat dissipation
is related to pressure-rise pattern.
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
4. Conclussions

• A 2-dimionsional axisymmetric CFD model for
  predicting fast filling process of 70 MPa HFCV
  cylinder has been presented. And by changing the
  pressure-rise pattern and the filling time, the
  thermodynamic response of 70 MPa fast filling
  process has been explored. Some conclusions are
  described as follows
• Remarkable temperature gradient can be found in
  the jet path and interlaminar area between the
  aluminum alloy liner and CFRP layer.
• For linear pressure-rise pattern with different
  filling time, the final maximum gas temperature
  increases with the decreasing of the filling
  time.
• For different pressure-rise patterns with the
  same filling time, difference of the final
  maximum gas temperature among the cases is small.

Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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4th International Conference on Hydrogen Safety
September 12-14, 2011 San
Francisco, California, USA
Engineering Research Center of High Pressure
Process Equipment and Safety
Numerical study on fast filling of 70 MPa
hydrogen vehicle cylinder
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• Tel [phone]
• Fax[phone]
• Email jyzh_at_zju.edu.cn
• Address Institute of Process Equipment,
  Zhejiang University, 38Zheda Road, Hangzhou,
  P.R. China, 310027.

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