Impact of non-ideality on mixing of hydrocarbons and water at supercritical or near-critical conditions

He, Ping; Raghavan, Ashwin; Ghoniem, Ahmed F.

doi:10.1016/j.supflu.2015.03.017

Cited by 15 publications

(10 citation statements)

References 44 publications

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“…In the plots of Figure 5, the mole fraction of the fuel (i.e., the heavy hydrocarbon) is given for the liquid and the gas phase as a function of chamber pressure (in terms of the reduced pressure of the fuel, p r = p/p c, f uel ) and temperature. The results prove that two-phase behavior can be predicted at pressures higher than the critical pressure of the injected fuel, similar to other works implementing the Redlich-Kwong, the Soave-Redlich-Kwong or the Peng-Robinson equations of state [9,11,14,[34][35][36][37]. As pressure is increased, the dissolution of the oxidizer (i.e., light gas) in the liquid phase is enhanced.…”

Section: Phase Equilibriumsupporting

confidence: 87%

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Transient behavior near liquid-gas interface at supercritical pressure

Poblador-Ibanez

Sirignano

2018

International Journal of Heat and Mass Transfer

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Numerical heat and mass transfer analysis of a configuration where a cool liquid hydrocarbon is suddenly introduced to a hotter gas at supercritical pressure shows that a well-defined phase equilibrium can be established before substantial growth of typical hydrodynamic instabilities. The equilibrium values at the interface quickly reach near-steady values. Sufficiently thick diffusion layers form quickly around the liquid-gas interface (e.g., 3-10 µm for the liquid phase and 10-30 µm for the gas phase in 10-100 µs), where density variations become increasingly important with pressure as mixing of species is enhanced. While the hydrocarbon vaporizes and the gas condenses for all analyzed pressures, the net mass flux across the interface reverses as pressure is increased, showing that a clear vaporization-driven problem at low pressures may present condensation at higher pressures. This is achieved while heat still conducts from gas to liquid. Analysis of fundamental thermodynamic laws on a fixed-mass element containing the diffusion layers proves the thermodynamic viability of the obtained results.

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Section: Phase Equilibriumsupporting

confidence: 87%

“…It becomes important not to mix non-ideal and complex models with simpler ones, since better accuracy in these fluid states can be lost. For instance, He et al [11] show the effects of non-idealities on the diffusion process, where the so-called diffusion barrier can be identified.…”

Section: Introductionmentioning

confidence: 99%

Transient behavior near liquid-gas interface at supercritical pressure

Poblador-Ibanez

Sirignano

2018

International Journal of Heat and Mass Transfer

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“…Rigorously, the non ideal mixing of the species should be taken into account. Some authors [18][19][20][21] have shown that in the case of diffusionpredominant mixing close and above the critical point of the mixture, the effects of the non ideal mixing driving force is significant, especially at high temperature. In our case, we checked that the effects of the non ideal mixing driving force were negligible.…”

Section: Hydrodynamicsmentioning

confidence: 99%

“…t m = 0.0034 • ϵ −0.5 (18) The performance of other micromixers are collected in the literature [32,[34][35][36][37][38][39] and their mixing times are mostly higher than 1 ms. It should be reminded that all experiments previously published have been performed…”

Section: Micromixing Time and Mixing Performance Comparisonmentioning

confidence: 99%

Mixing intensification under turbulent conditions in a high pressure microreactor

Zhang

Marre

Erriguible

2020

Chemical Engineering Journal

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The turbulent mixing of two miscible fluids is investigated in a high pressure (HP) coflow microreactor operated at 100 bar. Ethanol and CO 2 are selected as model solvents to mimic the final targeted application, i.e.: a supercritical antisolvent process at microscale (µSAS). We first demonstrate experimentally that turbulent mixing can be reached in a microchannel using HP microfluidics. A computational fluid dynamic (CFD) model, performed using direct numerical simulation (DNS) down to the Kolmogorov scale has been applied for the turbulent mixing simulations. The effects of the main operating parameters on the final mixing efficiency has been studied, namely: the temperature, the fluid flowrates, the microchannel dimensions and the capillary inner and outer diameters. According to a predefined intensity of segregation, the characteristic mixing times are determined and used for determining mixing efficiency. The ratio of the total mixing time to the diffusion time depends on the ratio of the kinetic energies (the outer fluid to the inner one). The obtained micromixing times have been related to the turbulent energy dissipation rate ϵ, calculated directly from the velocity fluctuations. The mixing intensification is obtained with much lower characteristic mixing times in the microreactor (one order of magnitude) than previously reported. This fundamental study is an indispensable guidance for several processes, including the µSAS applications.

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“…∂y . Binary diffusion coefficients are obtained from high-pressure correlations and the thermodynamic factor, Γ, representing non-idealities in the diffusion process, is included in the diffusion driving force, d i [15,24,26]. The thermodynamic factor tends to 1 for an ideal mixture and it is identical to 1 for a pure substance.…”

Section: Transport Propertiesmentioning

confidence: 99%

Two-phase developing laminar mixing layer at supercritical pressures

Davis¹,

Poblador-Ibanez²,

Sirignano³

2019

Preprint

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Numerical analysis of a shear layer between a cool liquid hydrocarbon and a hotter oxygen gas at supercritical pressures shows that a well-defined phase equilibrium can be established. Variable properties are considered with the product ρµ in the gas phase showing a nearly constant result. Sufficiently thick diffusion layers form around the liquid-gas interface for the selected free-stream velocities at a streamwise distance of x = 1 cm for different pressures (i.e., 10 -18 µm in the liquid phase and 30 -160 µm in the gas phase). While molecules are exchanged for both species at all pressures, net mass flux across the interface shifts as pressure is increased. Net vaporization occurs for low pressures while net condensation occurs at higher pressures. For a mixture of n-decane and oxygen, the transition occurs around 50 bar. The equilibrium values at the interface quickly reach their asymptotes. For all cases, profiles of diffusing-advecting quantities collapse to a similar solution (i.e., function of one independent variable). However, similarity for the normalized results from cases with different boundary conditions is lost when comparing different pressure or temperature cases to each other as the thermodynamics and interface conditions change.

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Impact of non-ideality on mixing of hydrocarbons and water at supercritical or near-critical conditions

Cited by 15 publications

References 44 publications

Transient behavior near liquid-gas interface at supercritical pressure

Transient behavior near liquid-gas interface at supercritical pressure

Mixing intensification under turbulent conditions in a high pressure microreactor

Two-phase developing laminar mixing layer at supercritical pressures

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