An engineering tool for discharge calculations

1 PRESLHY dissemination conference, 5-6 May 2021

Pre-normative REsearch for Safe use of Liquid HYdrogen

An engineering tool for discharge

calculations

PRESLHY dissemination conference, 5-6 May 2021, online event

Alexandros Venetsanos, NCSRD


Outline

− Models

− Implementation

− Validation

− Application

− Conclusions

− Acknowledgements

Models - Implementation - Validation - Application – Conclusions - Acknowledgements


Models – Physical properties

− Substances: n-H2, p-H2, CH4, H20, CO2, NH3

− EoS: HFE, 3rd-order RKMC, Abel-Noble, Ideal gas

− Phase change: HEM and various HNEM

− Spinodal line calculations

− Various state definition modes (P,T,x) or (P,h) or (P,s) or (P,ρ) etc. +

Multiple states definition from files

− States visualization on TS, PT and PV charts

Models - Implementation - Validation - Application - Conclusions - Acknowledgements


Models – Release calcs

− Storage Tank

− Either:

− Given tank: (real rank stagnation conditions with time from files) OR

− Modelled tank: Transient mass + energy balance (either entropy or

internal energy) with / without wall heat transfer + thermal equilibrium +

homogeneous or stratified conditions + release from top or bottom

− Isentropic change from tank stagnation state to discharge line inlet

− Discharge line

− Discharge line composed of a user defined number of pipe elements with

discretization for each element + High resolution near min cross section line

where Ma = 1 is expected.

− Steady momentum equation with friction, area change, extra resistances

(fittings) + energy equation with / without wall heat transfer.

− Fictitious nozzle

− 7 different models from literature



Implementation

− Numerics

− Brent’s iterative root finding algorithms

− Golden section min-maximization algorithms

− PIF algorithm for choked flow calculations (Ma = 1 is output not input

condition).

− Machine precision (10-16)

− Simulation time: few seconds for PIF algorithm and order of minutes for a full

blow-down.

− Programming

− Fortran dynamic link libraries

− Python interface (using ctypes+tkinter)

− Early version implemented in NetTools / eLab


https://www.youtube.com/watch?v=3iTAt3HdAWI

https://www.youtube.com/watch?v=3iTAt3HdAWI


Validation (1/5)


NASA CLH2 critical flow experiments (22 tests) with elliptical

converging-diverging nozzle @ P0 = 12.9-58.9 bar, T0 = 27.2-32.3 K

Simoneau and Hendricks (1979).

Venetsanos, Homogeneous non-equilibrium two-phase choked flow modelling, Int. J. of Hydrogen

Energy, 43 (2018), 22715-22726

P0=12.9bar, T0=30.7K


Validation (2/5)


Super Moby Dick experiments for liquid water,@ 20 bar, 212.3 C,

Jeandey et al., Report TT-163, (1981),

CEA, Grenoble.

Venetsanos, Choked two-phase flow with account of discharge line effects, ICHS-8, 2019


Validation (3/5)


INERIS CGH2 experiments, @ 900 bar, ambient temperature

25 dm³ type-IV tank, 10 m line, 10mm ID ending to a 2 mm ID nozzle

Proust et al., IJHE, (2011)

Venetsanos et al., Cryogenic and ambient gaseous hydrogen blowdown with discharge line effects,

ICHS-9, 2021


Validation (4/5)

Models - Implementation - Validation - Application - Conclusions - Closure

DISCHA CGH2 experiments, @ 200 bar, cold (80 K) and warm

(ambient temp.), 2.815 dm³ steel tank, 39 cm line, 9 mm ID ending to

0.5, 1, 2 and 4 mm ID nozzles,

Friedrich et al. PRESLHY D3.4 (2019)

Venetsanos et al., Cryogenic and ambient gaseous hydrogen blowdown with discharge line effects,

ICHS-9, 2021


Validation (5/5)


HSE LH2 experiments, @ 2 and 6 bara (sub-cooled),

23 m line, 1 inch ID and 1, 1/2, 1/4 inch ID nozzles

Lyons et al. PRESLHY D3.6 (2020)

Venetsanos et al., Discharge modeling of large scale LH2 experiments with an engineering tool,

ICHS-9, 2021

Nozzle

diameter

(mm)

2 bara 6 bara

Const

densityHNEM HEM

Const

densityHNEM HEM

25.4 3.4 3.3 1.9 9.0 8.5 7.1

12.7 11.6 11.5 7.9 0.1 -0.3 -3.3

6.35 13.4 12.7 9.6

Relative error (%) between predicted and experimental mass flow

rate (positive for overestimation)


Application – HFE versus ABN (1/3)


Abel-Noble (ABN) implemented with cp(T) of ideal gas and ABN

enthalpy both at stagnation and nozzle.

P (bar) HFE Abel-Noble Error %

10 618.49 618.25 -0.04

100 6125.72 6105.03 -0.34

200 12112.90 12046.82 -0.55

350 20819.48 20680.72 -0.67

500 29198.51 29011.84 -0.64

700 39891.43 39700.58 -0.48

900 50087.74 49963.19 -0.25

1000 55017.12 54949.99 -0.12

P (bar) HFE Abel-Noble Error %

10 1126.31 1113.99 -1.09

100 11738.09 10736.63 -8.53

200 23383.71 20697.64 -11.49

350 38885.18 34494.43 -11.29

500 52267.89 47203.46 -9.69

700 67834.88 62829.07 -7.38

900 81611.04 77259.51 -5.33

1000 87998.65 84103.33 -4.43

T=100 K

T=298.15 K

Choked conditions (orange dots)

Stagnation conditions (blue dots)


Application – Discharge line effects (2a/3)


• Line length effect

• Nozzle size effect

Predicted H2 mass flow rate (HFE EoS)


Application – Discharge line effect (2b/3)


Distribution of physical variables along the 15m line, 4mm ID line, 700bar, 280 K

HFE, EoS


Application – Fictitious nozzle (3/3)


Model

idMach=1

Momentum

balanceAdiabatic

Ambient

temperatureIsothermal Isentropic

1

2

3

4

5

6

7

7 fictitious nozzle models

Venetsanos et al., PRESLHY D3.1 (2019)

Stagnation (S) P=100 bar, T=293.15, 80 and 50 K, Nozzle (N)


Conclusions / Future work

− The developed tool can be applied for:

− Consequence assessment (input to dispersion codes)

− Design of experiments / systems

− Research / Education

− Future work topics

− Further validation

− HNEM modeling

− Tank heat transfer

− Boiling heat transfer (tank+line)

− Two-layer two-phase tank modeling

− Interface + algorithms optimization



The PRESLHY project has received funding from the Fuel Cells and

Hydrogen 2 Joint Undertaking under the European Union’s Horizon 2020

research and innovation program under the grant agreement No 779613.


Acknowledgement

An engineering tool for discharge calculations

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