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A model has been developed and implemented in the software package BoilFAST that allows for reliable calculations of the self-pressurization and boil-off losses for liquid hydrogen in different tank geometries and thermal insulation systems. The model accounts for the heat transfer from the vapor to the liquid phase, incorporates realistic heat transfer mechanisms, and uses reference equations of state to calculate thermodynamic properties. The model is validated by testing against a variety of scenarios using multiple sets of industrially relevant data for liquid hydrogen (LH2), including self-pressurization and densification data obtained from an LH2 storage tank at NASA’s Kennedy Space Centre. The model exhibits excellent agreement with experimental and industrial data across a range of simulated conditions, including zero boil-off in microgravity environments, self-pressurization of a stored mass of LH2, and boil-off from a previously pressurized tank as it is being relieved of vapor.

We report the speeds of sound in liquid toluene (methylbenzene) measured using double-path pulse-echo apparatus independently at The University of Western Australia (UWA) and Imperial College London (ICL). The UWA data were measured at temperatures between (306 and 423) K and at pressures up to 65 MPa with standard uncertainties of between (0.02 and 0.04)%. At ICL, measurements were made at temperatures between (283.15 and 473.15) K and at pressures up to 390 MPa with standard uncertainty of 0.06%. By means of thermodynamic integration, the measured sound-speed data were combined with initial density and isobaric heat capacity values obtained from extrapolated experimental data to derive a comprehensive set of thermodynamic properties of liquid toluene over the full measurement range. Extensive uncertainty analysis was performed by studying the response of derived properties to constant and dynamic perturbations of the sound-speed surface, as well as the initial density and heat capacity values. The relative expanded uncertainties at 95% confidence of derived density, isobaric heat capacity, isobaric expansivity, isochoric heat capacity, isothermal compressibility, isentropic compressibility, thermal pressure coefficient and internal pressure were estimated to be (0.2, 2.2, 1.0, 2.6, 0.6, 0.2, 1.0 and 2.7)%, respectively. Due to their low uncertainty, these data and derived properties should be well suited for developing a new and improved fundamental Helmholtz equation of state for toluene.

The prediction of thermophysical properties for hydrocarbon mixtures at high pressures, and conditions near the phase boundary or critical point is challenging. However, natural gas processing applications have an increasing need for reliable property predictions at such conditions. In this work, thermal conductivity measurements of three ternary mixtures (methane + propane with heptane at concentration up to 15 mol%) were carried out with a transient hot-wire apparatus. Measurements of the three ternary mixtures were conducted over the temperature range from (199.1 to 424.2) K and the pressure range between (10.41 and 31.55) MPa at single phase conditions with a relative combined expanded uncertainty (k = 2) between 0.015 and 0.056. The measured values were compared to predictions made with the extended corresponding states (ECS) model and SUPERTRAPP model implemented in the software packages REFPROP 10 and MultiFlash 6.2, respectively. The relative deviations of the measured thermal conductivities from the model predictions were (− 5.7 to + 2.4) % for the ECS model and (− 21.1 to − 0.6) % for the SUPERTRAPP model. This indicates the latter, older model should not be used to estimate natural gas thermal conductivities, particularly at high pressure conditions, while the ECS model is capable of representing the data within their uncertainty with no parameter tuning required.

Knowledge of thermodynamic properties of aqueous solutions of CO 2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO 2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO 2 . We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO 2 for mole fractions of CO 2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO 2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO 2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO 2 . Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO 2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO 2 gas.

Accurate phase equilibrium data for mixtures of eco-friendly but mildly-flammable refrigerants with inert components like CO 2 will help the refrigeration industry safely employ working fluids with 80 % less global warming potential than those of many widely-used refrigerants. In this work, a visual high-pressure measurement setup was used to measure solid–fluid equilibrium (SFE) of HFC-32 + CO 2 binary systems at temperatures between (132 and 217) K. The experimental data show a eutectic composition of around 11 mol % CO 2 with a eutectic temperature of 131.9 K at solid–liquid–vapour (SLVE) condition. Measured SLVE and solid–liquid equilibrium data were used to tune a thermodynamic model implemented in the ThermoFAST software package by adjusting the binary interaction parameter (BIP) in the Peng–Robinson equation of state. The tuned model represents the measured melting points for binary mixtures with a root mean square deviation (RMSD) of 3.2 K, which is 60 % less than achieved with the default BIP. An RMSD of 0.5 K was obtained using the tuned model for the mixtures with CO 2 fractions over 28 mol % relative to an RMSD of 3.4 K obtained with the default model. The new property data and improved model presented in this work will help avoid solid deposition risk in cryogenic applications of the HFC-32 + CO 2 binary system and promote wider applications of more environmentally-friendly refrigerant mixtures.