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Liquid-phase and vapour-phase densities are reported for the binary refrigerant mixtures (R125 + R1234ze(E)), (R134a + R1234ze(E)), (R143a + R1234ze(E)), (R1234ze(E) + R1234yf), (R125 + R1234yf), (R143a + R1234yf) and (R125 + R152a). The measurements span temperatures from (252 to 294) K and pressures from (0.8 to 4.2) MPa. Vapour-liquid equilibria (VLE) and liquid isobaric heat capacities are also reported for some mixtures. These measurements and previously published data were used to tune binary interaction parameters in existing Helmholtz energy models. Significant improvements in the predicted densities were achieved, for example the root mean squared relative deviation decreased from 0.33 % to 0.021 % for (R143a + R1234yf). The most significant improvement in the description of VLE occurred for (R1234yf + R1234ze(E)) where the root mean squared deviation in the predicted vapour phase compositions decreased from 0.010 to 0.00084 (a factor of 12).

Water-in-crude oil emulsions are an increasing problem during production. Essential to any emulsion breaking method is an ability to accurately measure droplet size distributions; this is rendered extremely difficult given that the samples are both concentrated and opaque. Here, we systematically consider the use of a standard, low-field benchtop nuclear magnetic resonance (NMR) apparatus to accurately measure the droplet size distributions. Such measurements are challenging because the NMR signal from the oil phase erroneously contributes to the measured water droplet size distribution. Conventionally, the oilphase signal is nulled-out based on differences in the NMR T 1 relaxation parameter between water and oil. However, in the case of crude oil, the oil presents a broad T 1 distribution, rendering this approach infeasible. On the basis of this oil T 1 distribution, we present an optimization routine that adjusts various NMR measurement timing parameters [observation time (Δ) and inversion time (T inv )] to effectively eliminate this erroneous crude oil contribution. An implementation of this optimization routine was validated against measurements performed using unambiguous chemical-shift selection of the water (droplet) signal, as would conventionally be provided by high-field superconducting NMR spectrometers. We finally demonstrate successful droplet sizing of a range of water-in-crude oil emulsions.

Benchtop nuclear magnetic resonance (NMR) pulsed field gradient (PFG) and relaxation measurements were used to monitor the clathrate hydrate shell growth occurring in water droplets dispersed in a continuous cyclopentane phase. These techniques allowed the growth of hydrate inside the opaque exterior shell to be monitored and, hence, information about the evolution of the shell's morphology to be deduced. NMR relaxation measurements were primarily used to monitor the hydrate shell growth kinetics, while PFG NMR diffusion experiments were used to determine the nominal droplet size distribution (DSD) of the unconverted water inside the shell core. A comparison of mean droplet sizes obtained directly via PFG NMR and independently deduced from relaxation measurements showed that the assumption of the shell model-a perfect spherical core of unconverted water-for these hydrate droplet systems is correct, but only after approximately 24 h of shell growth. Initially, hydrate growth is faster and heat-transfer-limited, leading to porous shells with surface areas larger than that of spheres with equivalent volumes. Subsequently, the hydrate growth rate becomes mass-transfer-limited, and the shells become thicker, spherical, and less porous.

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