Periodic Reporting for period 1 - ThermoPropHy (Thermodynamic Properties for Hydrogen Liquefaction and Processing)
Reporting period: 2022-10-01 to 2025-03-31
Hydrogen plays a prominent role in all concepts for CO2 mitigation; technologies for generation and for liquefaction of hydrogen need to be scaled up by orders of magnitude. This scale up has to rely on simulations of innovative processes, which are necessarily based on thermodynamic property models. An analysis of the available models indicates that properties of hydrogen are described with one order of magnitude larger uncertainty than properties of well-known fluids. Experience with process-simulation based scale-up shows that these uncertainties will likely result in large additional costs and delays.
To improve the description of properties of hydrogen and to enable the application of advanced liquefaction concepts, fundamental breakthroughs are required with regard to the metrology of fluids at cryogenic temperatures and with regard to accurate modelling of these complex systems – ThermoPropHy addresses this pioneering scientific work.
To improve the description of properties of hydrogen and to enable the application of advanced liquefaction concepts, fundamental breakthroughs are required with regard to the metrology of fluids at cryogenic temperatures and with regard to accurate modelling of these complex systems – ThermoPropHy addresses this pioneering scientific work.
Setup of a Highly-Accurate Cryogenic Densimeter, April 2025:
The new Magnetic Suspension Balance (MSB) is tested in our laboratories. The revised cryostat design requires a long thin metal wire for the connection between sinker and MSB to reduce surface tension effects. The control of the MSB cannot handle long thin wires. Due to oscillations the balance readings fluctuate, do not become stable. A solution was found that allows for stable balance readings with minimal surface-tension effects.
Thermometers and the corresponding resistance bridges have been delivered. A calibration plan has been developed with PTB; the thermometers are at PTB by now. The secondary Cernox thermometers, which will be used for the measurement of temperature gradients in the cell, will be calibrated against the PRTs by ourselves.
The thermal design of the measuring cell and of the pre-cooling pipe has been finalized. Finite-element heat transfer calculations prove that it is possible to position the catalyst required for ortho/para conversion in a supply pipe of the measuring cell rather than in the cell.
The production of the equipment for helium handling is completed. The equipment is currently tested at the labs of the manufacturer. At RUB, the equipment for helium recycling has been installed and tested.
Investigations on the dynamics of the ortho/para conversion show that it would be very valuable to measure the ortho/para distribution of the off-gas from the measuring cell. In cooperation with colleagues at the University of Western Australia (UWA) in Perth, a concept is beeing developed to measure the ortho/para distribution. The corresponding Raman measurements have high priority by now, since they are also required for measurements with our existing densimeter down to 100 K. We plan to send a PhD candidate to UWA for three months from August on to gather experience with this measurement technology.
Experimental Campaigns with Established Equipment, April 2025:
Further measurements with our existing low-temperature densimeter confirmed the results obtained for the system helium/neon. First measurements were carried out for another relevant pre-cooling mixture, for neon/argon. These measurements show that the current reference equation of state for mixtures of helium, neon and argon does not accurately describe properties in the homogeneous region of the system neon/argon as well. Measurements are ongoing. Mixtures are currently prepared to investigate the third system, the system helium/argon.
Viscosity measurements for hydrogen and for mixtures of hydrogen with carbon dioxide, methane and ethane (impurities that can be observed in blue-hydrogen production) are completed, the results are published.
Modelling of Hydrogen Properties, April 2025:
Comparisons between heat capacities calculated based on an analysis of experimentally determined energy levels (by spectroscopy), on energy levels calculated from fits to spectroscopic data and on ab initio calculated energy levels resulted in an improved understanding of the uncertainty of the ideal gas heat capacities and of the temperature dependence of the equilibrium composition. The ideal-gas part of the current reference equation of state for hydrogen is based on an unsuitable functional form. A more suitable and numerically less demanding functional form has been identified and will be used as basis for the new reference equations of state.
Measurements with our low-temperature densimeter down to 100 K have improved the data base for mixtures of helium and neon and for mixtures of neon and argon. Based on the new data and on literature data for phase equilibria, mixture models are being developed.
The new Magnetic Suspension Balance (MSB) is tested in our laboratories. The revised cryostat design requires a long thin metal wire for the connection between sinker and MSB to reduce surface tension effects. The control of the MSB cannot handle long thin wires. Due to oscillations the balance readings fluctuate, do not become stable. A solution was found that allows for stable balance readings with minimal surface-tension effects.
Thermometers and the corresponding resistance bridges have been delivered. A calibration plan has been developed with PTB; the thermometers are at PTB by now. The secondary Cernox thermometers, which will be used for the measurement of temperature gradients in the cell, will be calibrated against the PRTs by ourselves.
The thermal design of the measuring cell and of the pre-cooling pipe has been finalized. Finite-element heat transfer calculations prove that it is possible to position the catalyst required for ortho/para conversion in a supply pipe of the measuring cell rather than in the cell.
The production of the equipment for helium handling is completed. The equipment is currently tested at the labs of the manufacturer. At RUB, the equipment for helium recycling has been installed and tested.
Investigations on the dynamics of the ortho/para conversion show that it would be very valuable to measure the ortho/para distribution of the off-gas from the measuring cell. In cooperation with colleagues at the University of Western Australia (UWA) in Perth, a concept is beeing developed to measure the ortho/para distribution. The corresponding Raman measurements have high priority by now, since they are also required for measurements with our existing densimeter down to 100 K. We plan to send a PhD candidate to UWA for three months from August on to gather experience with this measurement technology.
Experimental Campaigns with Established Equipment, April 2025:
Further measurements with our existing low-temperature densimeter confirmed the results obtained for the system helium/neon. First measurements were carried out for another relevant pre-cooling mixture, for neon/argon. These measurements show that the current reference equation of state for mixtures of helium, neon and argon does not accurately describe properties in the homogeneous region of the system neon/argon as well. Measurements are ongoing. Mixtures are currently prepared to investigate the third system, the system helium/argon.
Viscosity measurements for hydrogen and for mixtures of hydrogen with carbon dioxide, methane and ethane (impurities that can be observed in blue-hydrogen production) are completed, the results are published.
Modelling of Hydrogen Properties, April 2025:
Comparisons between heat capacities calculated based on an analysis of experimentally determined energy levels (by spectroscopy), on energy levels calculated from fits to spectroscopic data and on ab initio calculated energy levels resulted in an improved understanding of the uncertainty of the ideal gas heat capacities and of the temperature dependence of the equilibrium composition. The ideal-gas part of the current reference equation of state for hydrogen is based on an unsuitable functional form. A more suitable and numerically less demanding functional form has been identified and will be used as basis for the new reference equations of state.
Measurements with our low-temperature densimeter down to 100 K have improved the data base for mixtures of helium and neon and for mixtures of neon and argon. Based on the new data and on literature data for phase equilibria, mixture models are being developed.
Most Significant Achievements
The most important achievement of the work carried out in ThermoPropHy so far probably is that the highly accurate measurement of densities at LH2 temperatures with a magnetic suspension based densimeter is considered feasible by now.
Foreseen shortcomings of property models for hydrogen and for mixtures used to pre-cool hydrogen could be confirmed. New property models for mixtures of hydrogen with helium, neon and argon were established. The work on new mixture models for pre-cooling fluids (mixtures of helium, neon, and argon) makes good progress.
Work on the ideal-gas properties of ortho, para and equilibrium hydrogen has revealed shortcomings of the current reference equations of state. Both an improved data-base and a more suitable numerical functional form have been developed and are currently tested.
Knowledge Transfer:
With the colleagues at UWA a new cooperation was started to extend our densimeters by a Raman device capable to determine the ortho/para composition in the off gas of the measuring cell. Dr. E.W. Lemmon at NIST is closely involved in the development of improved mixture models for pre-cooling fluids.
The main route of non-academic knowledge transfer relevant for ThermoPropHy is the free software TREND (Thermodynamic Reference and Engineering Data). A new revision of TREND, TREND 6.0 will become available by end of May. This version will include the first results of ThermoPropHy, namely the new mixture models for pre-cooling fluids and for mixtures of hydrogen with noble gases, as well as the gas phase equation of state developed for hydrogen.
The most important achievement of the work carried out in ThermoPropHy so far probably is that the highly accurate measurement of densities at LH2 temperatures with a magnetic suspension based densimeter is considered feasible by now.
Foreseen shortcomings of property models for hydrogen and for mixtures used to pre-cool hydrogen could be confirmed. New property models for mixtures of hydrogen with helium, neon and argon were established. The work on new mixture models for pre-cooling fluids (mixtures of helium, neon, and argon) makes good progress.
Work on the ideal-gas properties of ortho, para and equilibrium hydrogen has revealed shortcomings of the current reference equations of state. Both an improved data-base and a more suitable numerical functional form have been developed and are currently tested.
Knowledge Transfer:
With the colleagues at UWA a new cooperation was started to extend our densimeters by a Raman device capable to determine the ortho/para composition in the off gas of the measuring cell. Dr. E.W. Lemmon at NIST is closely involved in the development of improved mixture models for pre-cooling fluids.
The main route of non-academic knowledge transfer relevant for ThermoPropHy is the free software TREND (Thermodynamic Reference and Engineering Data). A new revision of TREND, TREND 6.0 will become available by end of May. This version will include the first results of ThermoPropHy, namely the new mixture models for pre-cooling fluids and for mixtures of hydrogen with noble gases, as well as the gas phase equation of state developed for hydrogen.