Current Status of Thermodynamic Properties of Hydrogen

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Current Status of Thermodynamic Properties of
Hydrogen

• R.T Jacobsen, J.W. Leachman, and S.G. Penoncello
• Center for Applied Thermodynamic Studies (CATS)
• University of Idaho
• Moscow and Idaho Falls, Idaho, USA
• E.W. Lemmon
• Physical and Chemical Properties Division
• National Institute of Standards and Technology
  (NIST)
• Boulder, Colorado, USA

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Motivation

• Hydrogen Economy
• High temperature (gt1000 K) hydrogen generation
• Low temperature (lt21 K) hydrogen storage
• High pressure (gt70 MPa) hydrogen storage
• Current standards for hydrogen thermophysical
  properties published over 20 years ago.
• Assessment of standards and available
  experimental data.
• Available experimental data
• Comparisons of experimental data to calculated
  values of the standard.

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The Hydrogen Economy

• 2004 Production
• 50 million metric tons globally
• 48 by steam reforming natural gas
• Custody Transfer
• Rail and Barge
• Cryogenic Tankers
• Pipelines
• Utilization
• Chemical Production
• Petroleum Refining
• Fuel

Image take from California Fuel Cell
Partnership www.cafcp.org/fuel-vehl_map.html
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Properties Standard

• Hydrogen Equation of State
• Published in 1982
• Based on work during the 1970s through the early
  1980s at NIST
• Upper pressure limit 121 megapascals (MPa)
• Upper temperature limit 400 kelvin (K)
• Uses the IPTS-68 temperature scale

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Properties Standard (cont.)
Maximum Hydrogen Generation Process Temperatures
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Properties Standard (cont.)
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Hydrogen Behavior
Molecular Hydrogen H2
Normal
3 1
parahydrogen lower energy states can exist in
pure form
orthohydrogen higher energy states cannot exist
in pure form
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Hydrogen Behavior (cont.)

• Equilibrium Hydrogen
• Mixture with equilibrium concentration ratio at a
  given temperature.
• Normal Hydrogen
• Equilibrium hydrogen at room temperature
• 75 orthohydrogen, 25 parahydrogen
• Parahydrogen
• Assumed when mixture is 99.75 parahydrogen
• Equilibrium concentration at 19 K.

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Hydrogen Behavior (cont.)
Minimum parahydrogen concentration is 25
Temperature Dependence of Orthohydrogen to
Parahydrogen at an Equilibrium Concentration
Ratio.
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Hydrogen Behavior (cont.)

• The different species have different
  thermophysical properties!
• Largest differences between orthohydrogen and
  parahydrogen occur in properties dependent on
  rotational heat capacity.
• Enthalpy, entropy, heat capacities, thermal
  conductivity.
• Small differences in density.
• Vapor pressure and saturation properties also
  show small differences.

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Experimental Data

• Over 9000 hydrogen thermodynamic data points
  compiled.
• Normal hydrogen and parahydrogen shown in
  separate data maps and comparisons.

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P-?-T Data for Normal Hydrogen.
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Data from Liebenberg et al. and Matsuishi et al.
from 200-10840 MPa not included.
Speed of Sound Data for Normal Hydrogen.
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P-?-T Data for Parahydrogen.
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Speed of Sound Data for Parahydrogen.
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Calculated vs. Experimental

• Comparisons provide the basis for the accuracy
  and precision of the representation by the
  equation of state.
• Percent deviations of the data from those
  calculated are plotted versus pressure.

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Comparisons of Density Calculated with REFPROP
with Experimental Normal Hydrogen P-?-T Data
(?X vs. Pressure).
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Comparisons of Speed of Sound Calculated with
REFPROP with Experimental Normal Hydrogen Speed
of Sound Data (?X vs. Pressure).
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Comparisons of Density Calculated with REFPROP
with Experimental Parahydrogen P-?-T Data (?X
vs. Pressure).
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Comparisons of Speed of Sound Calculated with
REFPROP with Experimental Parahydrogen Speed of
Sound Data (?X vs. Pressure).
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Conclusions (General)

• In years since publication of standard
• Experimental measurements have improved
• Computer modeling techniques have improved
• The temperature scale has been updated to ITS-90
• Improvement of the hydrogen equation of state is
  probable.

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Conclusions (Normal Hydrogen)

• Scatter in vapor pressure measurements is up to 2
  .
• 1 set of liquid density measurements below 34 K
  exists.
• 1 set of P-?-T measurements exists in critical
  region from 32-50 K.
• Scarce P-?-T measurements exist between 400 and
  1200 K.
• Additional speed of sound measurements at low
  pressures and moderate temperatures are needed.
• 1 set of heat capacity measurements exist that
  display over 10 scatter.

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Conclusions (Parahydrogen)

• Data needs similar to normal hydrogen except
• Measurements of the speed of sound are available
  to 100 K.
• Heat capacity data available below 70 K.
• Large data set available near critical region to
  100 K.
• Heat capacity data above 70 K are needed.
• Some high accuracy P-?-T measurements over 100 K
  would be useful.

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Questions?
Image from General Motors
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Comparisons of Density Calculated with REFPROP
with Experimental Normal Hydrogen P-?-T Data
(?X vs. Temperature).
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Comparisons of Density Calculated with REFPROP
with Experimental Parahydrogen P-?-T Data (?X
vs. Temperature).
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Normal Hydrogen Vapor Pressure
Parahydrogen Vapor Pressure
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Parahydrogen Isochoric Heat Capacity
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Parahydrogen Isobaric Heat Capacity
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Parahydrogen Saturation Heat Capacity
Normal Hydrogen Isobaric Heat Capacity