A General Correlation between the Temperature-Dependent Solubility and Solute and Solvent Molar Masses in Binary n-Alkane Mixtures

An increasingly popular solution in the oil-industry is long-distance sub-sea transportation of unprocessed well-streams. This will commonly expose the oil to temperatures significantly below the reservoir temperature, and possibly below the wax appearance temperature, resulting in precipitation and depostion of solids. Being able to predict the temperature dependent solubility of paraffinic components in oil may thus be crucial for developing the oil-fields of the future. In this paper, published data for binary normal-alkane mixtures is reviewed. A total of 43 unique solute-solvent data-sets, obtained from a total of 24 papers, are revisited, and based on thermodynamic considerations and the experimental data it is demonstrated that there is a log-linear relationship between the solubility and the temperature. Linear regression is employed to 1) obtain data-set-specific solubility-temperature best-fit parameters and 2) obtain a general correlation between the solubility and the solvent and solute molar masses and the temperature. Finally, it is demonstrated that the developed correlation carries predictive power even for multi-component mixtures by utilizing solvent and solute average molar masses.Comment: Sumbitted to Fuel (Elsevier) in Oct. 2012 - Rejected. 27 pages, 6 figures (Fig. 6 contains 43 subfigures). Published data for binary normal-alkane mixtures reviewed. 43 solute-solvent data-sets, from 24 references are revisited. Linear regression used to establish a general correlation between solubility, solvent/solute molar masses and temperatur

Patient specific numerical simulation of flow in the human upper airways for assessing the effect of nasal surgery

The study is looking into the potential of using computational fluid dynamics (CFD) as a tool for predicting the outcome of surgery for alleviation of obstructive sleep apnea syndrome (OSAS). From pre- and post-operative computed tomography (CT) of an OSAS patient, the pre- and post-operative geometries of the patient's upper airways were generated. CFD simulations of laminar flow in the patient's upper airway show that after nasal surgery the mass flow is more evenly distributed between the two nasal cavities and the pressure drop over the nasal cavity has increased. The pressure change is contrary to clinical measurements that the CFD results have been compared with, and this is most likely related to the earlier steps of modelling - CT acquisition and geometry retrieval.Comment: Proceedings of the 12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, Trondheim, Norway, May 30th - June 1st, 2017, 11 pages, 13 figure

A Review of Experimental Solubilities and a General Correlation between the Temperature-Dependent Solubility and Solute and Solvent Molar Masses for Binary n-Alkane Mixtures

The solubility of a ”heavy” alkane (solute) in a ”light” alkane (solvent) is generally temperature dependent. Moreover, it is determined by the molar masses of the solute and solvent. In the current paper, published solubility data for binary normal-alkane mixtures is reviewed (solid-liquid equilibrium). A total of 43 unique solute-solvent data-sets, obtained from a total of 24 published experimental studies, are collected and presented in a systematic manner. Based on thermodynamic considerations and the experimental data, it is demonstrated that there is a log-linear relationship between the solubility and the temperature in the dilute range. Linear regression is employed to 1) obtain data-set-specific solubility-temperature best-fit parameters and 2) obtain a general correlation between the solubility and the solvent and solute molar masses and the temperature. Finally, it is demonstrated that the developed correlation carries predictive power even for multi-component mixtures by utilizing solvent and solute average molar masses.publishedVersio

A Review of Experimental Solubilities and a General Correlation between the Temperature-Dependent Solubility and Solute and Solvent Molar Masses for Binary n-Alkane Mixtures

The solubility of a ”heavy” alkane (solute) in a ”light” alkane (solvent) is generally temperature dependent. Moreover, it is determined by the molar masses of the solute and solvent. In the current paper, published solubility data for binary normal-alkane mixtures is reviewed (solid-liquid equilibrium). A total of 43 unique solute-solvent data-sets, obtained from a total of 24 published experimental studies, are collected and presented in a systematic manner. Based on thermodynamic considerations and the experimental data, it is demonstrated that there is a log-linear relationship between the solubility and the temperature in the dilute range. Linear regression is employed to 1) obtain data-set-specific solubility-temperature best-fit parameters and 2) obtain a general correlation between the solubility and the solvent and solute molar masses and the temperature. Finally, it is demonstrated that the developed correlation carries predictive power even for multi-component mixtures by utilizing solvent and solute average molar masses

An Analytical Mathematical Theoretical Study of Single-Well Push-Pull ”Echo” Tests

Analysis of stream-line-based formulations is exercised to develop a stream-line based semi-analytical model for the single-well push-pull test, taking into account natural ground-water drift. The model is employed to calculate the time of breakthrough for clean water and the end-time of tracer production in addition to the overall producing tracer concentration vs. time. Contradictory to traditional approaches to the problem, natural ground water drift is considered important and physical dispersion of the injectant front is considered negligible. As a main topic we study injection/production in unconfined homogeneously stratified aquifers of infinite areal extent, subject to natural groundwater drift. Injectant and in situ groundwater are assumed to be miscible, incompressible fluids with identical fluid properties. Only macroscopic flow is considered, and flow is assumed to experience no in situ fluid mixing (physical dispersion) so fluid interfaces remain sharp. Analytically obtained results are compared to field study data provided by Pickens and Grisak, finite difference numerical simulation data obtained by Coats et al., and stream-line based simulation data from Streamsim Inc.’s 3DSL. The excellent match to experimental data and close agreement with simulation data validate the physical dispersion-free method proposed. It is concluded that the semi-analytical stream-line based solution gives the theoretically true production profile, and that any disagreement with simulation data is due to numerical dispersion and/or a poorly built model, on the simulator side. Making use of the stream-line based semi-analytical model, it is shown that, for a given set of boundary values and test-parameters, there exists a theoretical maximum injection phase duration giving conservative tracer production. The model is employed to study the tracer production profiles as the injection phase duration is extended to values larger than this limit. The applicability of the onedimensional convection-dispersion equation on calculating apparent dispersivity Peclet numbers is studied, as the injection phase duration is increased, and it is shown how it fails to predict the volume of recoverable tracer and how it fails to fit the measured data. It is also shown how a strongly scale depending apparent dispersivity may occur in a model, with no physical dispersion, due to natural drift only. Stream-line patterns for a two-well transmission test in a naturally flowing aquifer is created, and studied as a function of natural ground-water drift direction. It has been indicated how the natural ground-water drift may have an even bigger impact on the two-well transmission test than on the single-well push-pull test

Capillary forces as a limiting factor for sawing of ultrathin silicon wafers by diamond multi-wire saw

Succeeding with ultrathin silicon wafer sawing by diamond multi-wire saw, is not only a matter of optimization; the challenges of thin wafer production and the capability limit have not yet been fully understood. In this work, we have seen that regular pairing of wires occurs when the wire-wire separation distance is reduced below some critical value. The wire pairing leads to wire jumps on the wire guide rolls, and if the run is not stopped, it leads to wire breakage. Moreover, it effectively obstructs the production of wafers thinner than the critical wire-wire distance. We suggest that the physical explanation to the observed limitations to ultrathin wafer sawing, by diamond multi-wire saw, is related to the capillary force acting on the wires due to the sawing liquid bridge connecting the wires. The hypothesis is supported by simplified mathematical modelling including capillary and spring forces between infinitely long, parallel wires. The calculations suggest that capillary forces are the main reason for wire pairing, and that wire pairing will occur when the wire distance is below some critical distance. This matches the observed, experimental behavior. The critical distance will vary with wafer saw design and operation. To succeed with cutting very thin wafers, we recommend using lower surface tension sawing fluid or even dry in-cut, to reduce the capillary forces and thus decrease the critical wire separation distance, and to reduce wire oscillations to decrease the probability of sub-critical wire-wire separation distance. To reduce the vibration amplitude, shorter distance between the wire guide rolls, thinner wires, and increased wire tension are suggested.publishedVersio

A Wall-Function Approach for Direct Precipitation/Crystallization Fouling in CFD Modelling

The main objective of this paper is to present a generic modelling framework, for the diffusive mass transport through the turbulent, reactive boundary layer of multi-component fluid mixtures that precipitate on the wall. The modelling is based on Maxwell-Stefan diffusion in multi-component mixtures, the relaxation to chemical equilibrium model, and the single-phase Navier-Stokes equations. Final-ly, turbulence is introduced by Reynolds-averaging. The governing equations are simplified in accordance with common assumptions of computational fluid dynamics (CFD), and b ased on the assumption that the over-all bulk flow is parallel to the wall, 1-dimensional equations for the species and heat transport perpendicular to the wall have been formulated. The equations are solved on a fine grid in order to fully re solve the boundary layer, and the effect of allowing/disallowing deposition and chemical reactions was investigated for a simplified test-case (4-component ideal mixture of perfect gasses capable of chemical reaction and sublimation fouling). The developed framework can be employed as a sub-grid model for direct precipitation/crystallization/solidification fouling in coarse grid CFD model

Investigation on scale formation in aluminium industry by means of a cold-finger

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-030-05864-7_87A cylindrical fouling probe or “cold-finger” has been used to investigate fouling from aluminium production off-gas. The probe was located upstream from the off-gas cleaning system. Surface deposits have been collected for further analysis by EPMA and XRD, and compared with off-gas dust and old scale samples collected in the same experimental site. Cross-section micrographs of the deposit surfaces have been obtained to highlight the differences in surface structures formed on the upstream and downstream faces of the cold-finger. Strongly adhered hard scale formed after only two days in the upstream face of the probe. Loosely attached deposits accumulated downstream, which consisted of distinguishable particles of Al 2 O 3 , spherical Cryolitic bath condensates and Ni-S phases. The hard scale was rich in small bath condensates (NaAlF 4 ) that form a tight network keeping together the larger particles. The deposition of those particles is suggested to be a key in scale formation. © 2019, The Minerals, Metals & Materials Society.acceptedVersio