U min ()= 0.2 kg.m-3 U max ()= 8 kg.m-3 U min ()= 0.5 kg.m-3 U max ()= 15 kg.m-3 U min ()= 0.4 kg.m-3 U max ()= 13 kg.m-3 U min ()= 0.1 kg.m-3 U max ()= 3 kg.m-3 U min ()= 0.1 kg.m-3 U max ()= 3 kg.m-3 U min ()= 0.1 kg.m-3 U max ()= 2 kg.m-3 U min ()= 0.2 kg.m-3 U max ()= 5 kg.m-3 U min ()= 0.1kg.m-3 U max ()= 2.5 kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3 p/MPa /kg.m-3
The densities of CO 2-R1234ze(E) (trans-1,3,3,3-tetrafluoroprop-1-ene) binary mixture were measured using VTD densitometer, Anton Paar DMA 512, in the gas, liquid and supercritical phases. Four compositions of mixtures: 21.3% CO 2 + 78.7% R1234ze(E), 40% CO 2 + 60% R1234ze(E), 59.6% CO 2 + 40.6% R1234ze(E) and 79.4% CO 2 + 20.6% R1234ze(E) were studied at seven temperatures between 283.32K and 353.02K and pressures up to 10MPa. The data were well correlated using the Peng-Robinson cubic equation of State using the Wong Sandler mixing rules involving the NRTL activity coefficient model, and the fundamental Helmholtz equation of state using the Kunz and Wagner mixing rules involving Helmholtz energy. The experimental and correlated phase compositions were compared. Both two models were adjusted on the VLE data, but the Helmholtz model is more accurate to the prediction of density than the Peng-Robinson model.
Knowledge of the dissociation conditions of mixed-gas hydrate systems is of great importance for scientific understanding (e.g. Clathrate hydrates in the outer solar system) and engineering applications (e.g. flow assurance, refrigeration and separation processes). In this work, CO 2 +O 2 hydrate dissociation points were measured at different O 2 mole fractions (11%, 32% and 50%) using isochoric pressure search method. The consistency of these new data was verified using the Clausius-Clapeyron relationship. The measurements performed for pressures up to 19 MPa overcome the lack of data for this system, and also allows to evaluate the model predictions from pure CO 2 hydrate to pure O 2 hydrate. To predict gas hydrate stability curves, in this work, the well-established hydrate theory of van der Waals and Platteeuw (vdWP) is combined with an electrolyte CPA-type Equation of State (e-PR-CPA EoS) which has been successfully used to represent with high accuracy the fluid phase equilibria (including gas solubility and water content) of complex systems containing gas, water and salt. The resulting model (e-PR-CPA + vdWP) was applied to the O 2 +H 2 O and CO 2 +H 2 O+(NaCl) systems by comparing with literature data. In the studied temperature range (>270K), the model predicts as expected a hydrate structure of type I for O 2 , CO 2 and their mixtures. An excellent reproduction of the measured data by this complete model was obtained without any additional adjustable parameters.
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