hydrogen – methane mixtures: dispersion and stratification studies a. marangon, m.n. carcassi

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

HYDROGEN – METHANE MIXTURES:DISPERSION AND STRATIFICATION STUDIES

A. Marangon, M.N. Carcassi

Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione (DIMNP),(DIMNP),

University of PisaUniversity of Pisa

Università di Pisa

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

Why the hydrogen – methane mixtures could represent the transition phase towards hydrogen economy?

Experience gained over many year of distribution and use of natural gas

(transportation, energy production, domestic application, etc.).

Greater acceptance by the Public Authority and general public with

respect to pure hydrogen.

Limited investment in the short term and a significant reduction in

emissions, both local and global (greenhouse gases).

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

UNIPI – DIMNP Research activities on HCNG mixtures: 10-90 and 30-70 %vol. hydrogen in methane.

Investigation of the diffusion and stratification properties in confined and

semi-confined environments (typical of most of the industrial and

commercial environments).

Investigation with the help of the gas-chromatography technique of the

tendency or less to separate in different layers for the mixture’s

constituents (hydrogen and methane).

CFD simulations of the experimental tests (not presented in the paper).

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

DESCRIPTION OF THE TEST FACILITY

Volume: ca. 25 m3

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

DESCRIPTION OF THE TEST FACILITY

Ventilation openings

0,063 m x 0,560 m each.

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

GAS SUPPLY AND INSTRUMENTATION:

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

OXYGEN SENSOR – GAS CHROMATOGRAPHY:

Immediate manual immission in the gas chromatograph

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

OXYGEN SENSOR - VENTILATION OPENINGS POSITION:

n.7 oxygen sensors

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

MIXTURE CONCENTRATION MEASURED BY THE OXYGEN SENSORS:

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

TEST MATRIX:

MIXTURE30 H2 – 70 CH4

MIXTURE10 H2 – 90 CH4

CVE TOTALLY CLOSED

CVE WITH 2 OPENINGS ON

OPPOSITE SIDES

CVE WITH 1 OPENING IN

THE BOTTOM PART

CVE WITH 1 OPENING IN THE UPPER

PART

X - X - - -

X - X - - -

X - X - - -

X - - X - -

- X X - - -

- X - X - -

- X - X - -

- X X - - -

X - X - - -

- X - - X -

- X - - - X

X - - - - X

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

SOME EXPERIMENTAL DATA:

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

CVE TOTALLY CLOSED: Release time: 530 s

Release flow rate: 2,016 g/s

TENDENCY TO HOMOGENEIZATION

STRATIFICATION NOT WELL DEFINED IN THE HORIZONTAL

PLANES

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

CVE TOTALLY CLOSED : Release time: 1580 s

Release flow rate: 1,16 g/s

TENDENCY TO HOMOGENEIZATION

STRATIFICATION WELL DEFINED

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

VENTILATION WITH OPENINGS ON OPPOSITE SIDES:

Release time: 2890 s

Release flow rate: 1,23 g/s

FAST DECREASE OF THE CONCENTRATION ONCE THE

RELEASE WAS STOPPED

STRATIFICATION WELL DEFINED

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

VENTILATION WITH ONE OPENING IN THE UPPER PART:

Release time: 2560 s

Release flow rate: 1,32 g/s

STRATIFICATION WELL DEFINED IN THE HORIZONTAL

PLANES

ΔT (int-ext)= 5 °C

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

VENTILATION WITH ONE OPENING IN THE UPPER PART:

Release time: 2750 s

Release flow rate: 1,31 g/s

ΔT (int-ext)= 15 °CSTRATIFICATION NOT WELL DEFINED IN THE HORIZONTAL PLANES

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

VENTILATION WITH ONE OPENING IN THE BOTTOM PART:

Release time: 2023 s

Release flow rate: 1,5 g/s

STRATIFICATION WELL DEFINED IN THE HORIZONTAL

PLANES

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

METHANE CONCENTRATION (sensors vs. gas chromatograph):

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

CONCLUSIONS:

In all the experiments a non homogeneous concentration was observed

within the CVE, both with and without natural ventilation and

independently of natural ventilation openings position.

For test carried out with a higher mixture release flow rate, the gas

concentration measured at the centre of the celing of the CVE (Sens. N.1 –

2,82 m above the release point), was higher than the concentration

measured by sensor located at the same height but not directly above the

release. Instead for smaller release flow rate the concentration was well

stratified in the horizontal planes.

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

CONCLUSIONS:

For test carried out without natural ventilation a tendency to

homogenization was observed over long residence time (more than 10000

seconds).

For test carried out with natural ventilation openings, both well defined

stratification in horizontal planes and not well defined (with concentration

higher far from the opening location) was observed. This phenomenon

depending on the ΔT between the internal volume of the CVE and the

external atmosphere (higher the ΔT, worst the stratification).

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

CONCLUSIONS:

Sample analysis with gas chromatograph showed that for the presented

experiment configurations and mixture’s residence time within the CVE,

the non separation between the mixture constituent gases (hydrogen and

methane).

ICHS 2011 - San Francisco, USA - September 12 -14

HYDROGEN – METHANE MIXTURES: DISPERSION AND STRATIFICATION STUDIES

THANK YOU.

Contact Author:

Alessia Marangon (UNIPI-ITALY)

a.marangon@ing.unipi.it

Presented by:

Martino Schiavetti (UNIPI-ITALY)

martino.schiavetti@ing.unipi.it