Mass Exchange Mechanisms Research Articles

Molecular insights into the synergistic mechanisms of hybrid CO2-surfactant thermal systems at heavy oil-water interfaces

A hybrid thermal recovery process is a promising EOR (Enhanced Oil Recovery) method and has been widely applied to post-steamed heavy oil reservoirs. Due to the complexity of High Temperature and High Pressure (HTHP) reservoir environments, Molecules Dynamics (MD) simulations are conducted to investigate the interfacial behavior between multiphase multicomponent fluids and heavy oil over a wide temperature range. We select CO2 and a cost-effective anionic surfactant, SDS (Sodium Dodecyl Sulfate), to build hybrid thermal systems. The interfacial behavior in different systems is characterized by the local density distribution, cluster analysis, hydrogen bond characters, solvent accessible surface area, and interaction energy. Systematic MD simulations reveal a two-step interfacial tension (IFT) reduction process stimulated by thermal migration. Both CO2 and SDS can achieve an IFT decrement with different mechanisms. Moreover, a co-addition of CO2 and SDS can further efficiently reduce the IFT. Average Reduced Density Gradient (aRDG) results reveal that a unique asphaltenes-SDS-CO2 structure improves the interfacial activities and mobility of the heavy oil phase through a bidirectional mass exchange mechanism, which ultimately realizes the most significant IFT decrement. Furthermore, an optimal concentration (10C–20S) in a hybrid thermal system is recommended because of its balanced performance. This work sheds insight into the synergistic effects of multiphase multicomponent thermal fluids on hybrid thermal systems, which will guide future field applications of hybrid thermal EOR processes.

The probabilistic nature of dune collisions in 2D

Abstract. Dunes are bedforms of different size and shape, appearing throughout aeolian, subaqueous and extraterrestrial environments. Collisions between dunes drive dune field evolution, and are a direct result of interacting dunes of different heights, travelling at different speeds. We perform 2D cellular automaton simulations of collisions between dune pairs migrating in a steady flow. Modelled collisions can result in either ejection, where dunes exchange mass before separating, or downstream- or upstream-dominant coalescence (merging of dunes). For each of these three elementary types of interaction, we identify the mass exchange mechanism and the distinctive intermediate morphologies. Surprisingly, we show that the collision outcome depends probabilistically on the initial dune area ratio r and can be described by a narrow sigmoidal function centred on r=1/2. Finally, we compare our simulations with laboratory experiments of dune collisions, finding good agreement concerning the intermediate morphology and the collision outcome. Our results can motivate further observational or experimental studies that validate our probabilistic collision predictions and fully determine the controls on the coalescence–ejection transition.

Эффект “магнитосферного клапана” в полярах

The mass-exchange process in close binary systems which appear as polars is discussed. We point out that the strong magnetic field of the white dwarf in these systems can under certain conditions prevent material from flowing through the L1 point operating as a “magnetospheric gate”. Using some best studied polars as an example we show that the conditions in which the flow through the L1 point is suppressed can be satisfied. A discussion on an alternative mass-exchange mechanism in this situation appears to be quite reasonable.

Identifying soil-plant interactions in a mixed-age orange orchard using electrical resistivity imaging

Background and aimsThe ever-increasing demand of fresh water from irrigated agriculture and the water scarcity condition that characterizes the Mediterranean region, encourages the adoption of efficient water saving strategies. In this study, the electrical resistivity imaging (ERI) technique was applied for characterizing the mass exchange mechanisms affecting the continuous soil-plant system of heterogeneous micro-irrigated orchards.MethodsTime-lapse ERI surveys were carried out in a multi-variety and mixed-age orange orchard located in Eastern Sicily (insular Italy). The time-lapse ERI monitoring was coupled with the use of independent soil water content (SWC) measurements.Results and conclusionsA clear relationship between the soil electrical resistivity (ER) and the measured SWC changes was identified in the soil under the mixed-age orchard (with an overall coefficient of determination value of 0.63). Specifically, this study highlights the dependency of SWC dynamics as function of tree age. Overall, an increase in ER was obtained in correspondence to the soil domain where the younger trees were located ( < = 3 years). This behaviour was inferred to result from the higher soil evaporation process active at these locations, due to less vegetation cover of the younger trees and, consequently to their lesser root extension in comparison to the mature trees ( > = 8 years). On the other hand, in mature trees, characterized by denser root biomass, there were more evident decreasing patterns of ER (i.e., greater changes in SWC), due to greater transpiration rates that caused lower initial SWC under these conditions in comparison to the younger trees.

Mass Exchange of Water and Soil on the Soil Surface in the Rainfall Splash Erosion

This research aims to unfold the mass exchange mechanism of water and soil on the soil surface in the rainfall splash erosion process. We regard the rainfall splash erosion process as a collision process between the raindrop and the soil particle on the soil interface. This recognition allows us to incorporate research approaches from the spring vibrator model, which has been developed for simulating the impact of liquid drops on solid surface. We further argue that because a same set of factors determine the splash amount and infiltration amount and it is relatively simpler to observe the infiltration amount, an investigation into the relationship between the splash amount and infiltration amount would be able to provide a new channel for quantifying the splash erosion. This recognition leads us to examining the relationship between single raindrop, rainfall kinetic energy and splash erosion from both theoretical and empirical angles, with an emphasis on the relationship between the infiltration amount and the splash erosion. Such an investigation would add value to the collective effort to establish mass exchange law in water-soil interface during rainfall splash erosion. It is found that during the rainfall splash process, the splash erosion is proportional to the rainfall kinetic energy; and has a linear relation to the infiltration amount, with the rainfall intensity as one of important parameters and the slope depending on the unit conversation of the infiltration amount and the splash erosion. If the units of two items are same, the slope is the ratio of the soil and water density, and the splash erosion velocity of the rainfall is half of the rainfall terminal velocity. The single raindrop kinetic energy and the splash erosion have a quadratic parabola relation, and the splash velocity is about 1/3 of single raindrop terminal velocity.

Modeling of an air-to-air exchanger with dual-core in cascade connection

With the current leaning towards finding effective solutions to maintain a good indoor air quality (IAQ) inside houses and buildings and to simultaneously reduce the energy consumption, air-to-air exchangers with heat/energy recovery have emerged as one of the promising technologies to provide a healthy and comfortable indoor environment. To deeply evaluate these systems performances, the present investigation focuses on modeling a combined ERV-HRV exchanger using the effectiveness-NTU (ε−NTU) method. To this end, a detailed mathematical model introducing heat and mass exchange mechanisms was developed and applied to predict the system energy recovery efficiency. To assess its suitability, the developed model was validated and compared to real measurements which carried out under the Atlantic Canada weather. The comparison findings disclosed that the developed model can predict the system performance with a maximum relative discrepancy less than 10%.• The detailed mathematical model including heat and mass exchange mechanisms was clearly developed using the ε−NTU approach in order to carefully predict the dual-core system performance in terms of sensible and latent recovery potential.• The developed model was validated against real data to evaluate its suitability and accuracy. Obtained results show that it could be satisfactory for predicting the dual-core system performances.• The ε−NTU approach adopted in this study could be a convenient method for modeling single or/and dual-core air-to-air heat/energy recovery systems.

Potential erosion capacity of gravity currents created by changing initial conditions

Abstract. We investigate to what extent the initial conditions (in terms of buoyancy and geometry) of saline gravity currents flowing over a horizontal bottom influence their runout and entrainment capacity. In particular, to what extent the effect of the introduction of an inclined channel reach, just upstream from the lock gate, influences the hydrodynamics of gravity currents and consequently its potential erosion capacity is still an open question. The investigation presented herein focuses on the unknown effects of an inclined lock on the geometry of the current, on the streamwise velocity, on bed shear stress, and on the mechanisms of entrainment and mass exchange. Gravity currents were reproduced in the laboratory through the lock-exchange technique, and systematic tests were performed with different initial densities, combined with five initial volumes of release on horizontal and sloped locks. The inclination of the upstream reach of the channel (the lock) was varied from 0 % to 16 %, while the lock length was reduced by up to 1∕4 of the initial reference case. We observed that the shape of the current is modified due to the enhanced entrainment of ambient water, which is the region of the current in which this happens most. A counterintuitive relation between slope and mean streamwise velocity was found, supporting previous findings that hypothesized that gravity currents flowing down small slopes experience an initial acceleration followed by a deceleration. For the steepest slope tested, two opposite mechanisms of mass exchange are identified and discussed, i.e., the current entrainment of water from the upper surface due to the enhanced friction at the interface and the head feeding by a rear-fed current. The bed shear stress and the corresponding potential erosion capacity are discussed, giving insights into the geomorphological implications of natural gravity currents caused in different topographic settings.

Water mass exchange at Ambon Bay based on trajectory model: a preliminary study

Ambon Bay is divided into two parts, Inner Ambon Bay (IAB) and Outer Ambon Bay (OAB) which separated by 10 m narrow canal called sill. It causes IAB and OAB has different water dynamics. Generally, circulation dynamics at Ambon Bay affected by upwelling process in Banda Sea during southeast monsoon. During that period, tidal upwelling brought high density water from thermocline layer in OAB to surface and enter the IAB. The mechanism of water mass exchange can be describe using three-dimensional trajectory model which evaluate the origin and movement of water particles. This preliminary study shows the particle movement during one tidal cycle based on trajectory model results. Verification result shows that model error is 2.32%. Preliminary results show that after one tidal cycle, particles predominantly move to OAB rather than enter IAB through western side of the sill.

Correction to: Mechanisms of Mass Exchange Between Light Oil and Petroleum Gas in Low-Permeability Reservoir Development Process

There is an error in the article metadata on SpringerLink, the first author's name is incorrect. It should read P. A. Gushchin.

Mechanisms of Mass Exchange Between Light Oiland Petroleum Gas in Low-Permeability Reservoir Development Process

It is shown that associated petroleum gas (APG) and the product of intrastratal transformation of air (by high-pressure air injection technology) are suitable for oil displacement from low-permeability, high-temperature light oil reservoirs. It was found that APG and air are effective gaseous agents miscible with oil, which are similar in oil-displacing properties. The minimum miscibility pressure (MMP) determination data are presented for an Upper Jurassic oil-APG system. The miscibility in the oil-APG system was achieved by the multicontact mechanism of interaction between oil and enriched gas. A new method is proposed for graphical determination of MMP as a function of gas breakthrough due to pressure, and a method for enhancing gas impact efficiency and for achieving miscibility at a pressure below the MMP, which consists in injection of a liquefied gas prefringe or a wide fraction of hydrocarbons, is validated.

Modelling the mass exchange dynamics of oceanic surface and subsurface oil

We propose a time dependent Eulerian model for sea surface entrainment, buoyancy transport and droplet dynamics of ocean oil. The model captures the microscale vertical oil mass exchanges in the neighborhood of the sea surface. This model is in turn part of an oil fate model designed to capture oil dynamics at large spatio-temporal scales typical of environmental studies. The adiabatic dynamics of the droplets are upscaled by a combination of filtering and stochastic parametrization. The upscaling addresses the computational burden of resolving the microscale. The upscaled droplet dynamics are tested against data and the mass exchange mechanism is incorporated into a nearshore oil transport model in order to highlight the importance of incorporating vertical mass exchanges and droplet distribution dynamics in predicting the distributing of shoaling oil.

Underwater noise emitted during small-scale air entrainment events

Abstract The breaking wave phenomenon significantly takes part in the mechanisms of mass, heat and gas exchange at the air-water boundary and depends on the wind velocity. Some of the energy dissipated during this process is converted into underwater sound emitted by oscillating gas bubbles and bubble plumes. However, the underwater noise accompanying the lowest wind speed conditions has received only little attention. This report describes a study aimed at advancing the knowledge of underwater noise emission from air bubbles injected during small-scale breaking events occurring on the water surface. Results of model experiments performed in a small tank are presented. The object of the research is the relationship between the generated noise and the dissipated potential energy of water poured into a tank filled with water of varying physical water properties. Additionally, the impact of various water properties such as salinity, surface tension or microscale gas bubbles was examined. The experiment revealed that noise spectra are affected by different water properties and most likely reflect the varying efficiency of bubble formation and bubble size spectra.

HEAT AND MASS TRANSFER AND RESISTANCE CHARACTERISTICS OF EVAPORATIVE AIR COOLER WITH HIGH FINNED-TUBE BUNDLES

A theoretical model was suggested and experimental analysis of heat and mass exchange mechanism of a high finned-tube evaporative air cooling device was made. Experiments showed that the heat transfer of the upper four rows of tubes was higher than that of the lower four rows. The upper and lower layers of the proportion of water spray experiments were carried out. In the experimental range, the higher the proportion of the upper water spray, the greater the overall heat transfer. Besides, evaporation and heat transfer of water film were not only related to the air flow and spray water intensity, but also were affected by the relative humidity of imported air, with decrease in the relative humidity of imported air decreased, and with evaporation and heat transfer between air and water film strengthened. According to the experiments, the correlations of evaporation loss and heat transfer were fitted by air flow, spray water intensity, and relative humidity, which showed close agreement with the experimental results to within ± 11% and ± 9%, respectively. The correlation of pressure drop in the high finned-tube bundle was related to air flow rate and the intensity of the spray water, and the fitting error was within ± 8%. This study was instructive for the design of wet air cooler with high finned-tube bundle.

Modeling Solute Mass Exchange between Pore Regions in Slurry‐Injected Soil Columns during Intermittent Irrigation

Core Ideas Water flow and solute transport models described solute leaching during slurry injection. Intermittent flow increased leaching of injected slurry compounds compared with steady flow. Mass exchange of slurry compounds during interruptions occurred from im‐ to mobile pore regions. Mass exchange between pore regions should be included in larger scale model predictions. Animal slurry application to agricultural land can be a threat to the quality of groundwater and nearby surface water bodies by percolation of solutes from slurry sources. We hypothesized that local‐scale processes, such as mass exchange between preferential flow paths and matrix pore regions, can play a substantial role in relation to slurry application and nutrient leaching. To improve understanding of these mass exchange mechanisms, soil column leaching data of nonreactive slurry components after injection of dairy slurry were analyzed under different initial and boundary conditions with single‐ and double‐porosity model approaches. The data set was from nine intact soil columns (20‐cm i.d., 20‐cm height) of the plow layer of arable loamy topsoil that were percolated under unsaturated steady‐flow conditions with a suction of 5 cm applied at the bottom. Both single‐ and double‐porosity water flow and mobile–immobile solute transport models could describe these experimental breakthrough curves. Rainfall interruptions mimicking more natural conditions and variably saturated intermittent flow led to higher leaching of injected slurry compounds than steady‐flow conditions. These observations could be explained by an increased mass exchange of dissolved injected slurry components from the immobile to the mobile pore water regions during interruptions. The results suggest that column tests under steady‐flow conditions could lead to false predictions of solute leaching after slurry injection in structured soils. Furthermore, local‐scale processes, such as mass exchange between pore regions, should be included in larger scale model predictions of nutrient losses from agricultural fields.

Ex situ calibration technique for simultaneous velocity and temperature measurements inside water droplets using temperature-sensitive particles

Phosphorescence-based temperature measurements usually employ in situ calibration in macro-scale flow domains. However, the application of conventional in situ calibration in millimetre scales such as in 2 mm droplets is difficult because temperature probing using an intrusive technique such as thermocouple-based measurement can deform a droplet interface and even its integrity. Therefore, in this paper we propose an ex situ calibration technique for combined 2D fluid temperature and flow velocity measurements inside pendant droplets using thermographic phosphorescence and particle image velocimetry. This calibration technique has the potential to perform measurements not only inside droplets but also in other small-scale fluid domains that are sensitive to intrusive temperature probing. To develop this technique, the effect of local phosphorescence intensity on the phosphorescence decay constant (initial intensity effect) was studied and quantified. We observed that the phosphorescence light intensity of the first image among the decay image series affects the local decay constants as the coefficient of a half sigmoid function. This novel ex situ calibration technique was used to investigate high-spatial-resolution temperature and flow velocity distributions inside a pendant water droplet located in an air stream, and an anti-distortion algorithm was used to correct the optical distortion induced by the curved surface of the droplet. The measured temperature and velocity fields were found to be reasonable and consistent with those obtained in previous studies. The proposed technique is expected to be useful in conducting further investigations on the mechanisms of heat and mass transfers between droplets and carrier gases. Furthermore, it can potentially improve our understanding of the heat and mass exchange mechanisms within a droplet’s internal flow structures and temperature gradients.

Influence of Thermal Diffusion on the Hysteresis Area of Hydrogen Impurities’ Catalytic Combustion on Platinum Wire

A complex investigation of the hysteresis mechanisms of heat and mass exchange and catalytic flameless combustion of hydrogen-air mixtures on platinum’s particles and wires. Thermal diffusion of hydrogen does not affect the critical conditions for self-ignition mixture unlike conditions extinction mixture. Method is proposed the analytical determination of the hysteresis areas heat and mass exchange particles (wires) catalyst. Inside the areas there is a catalytic ignition, and outside - stationary states of oxidation and catalytic combustion of combustible gas in the air.

Influence of the Local Cross-Streamlined Obstacles on the Velocity and Pressure Fluctuations

Background. Developing means to enhance the effectiveness of mass and heat transfer processes on streamlined surfaces and their hydroacoustic qualities in the objects of power, aerospace and marine engineering. Objective. The purpose of the research is to determine the formation features and space-time characteristics of the velocity and wall-pressure fluctuation fields in flows above and on the streamlined surfaces with local obstacles as the cross-streamlined half-cylindrical trench on a flat surface and circular obstacle on the flexible longitudinal hydroacoustic antenna surface. Methods. The research was carried out by means of hot-wire and hydroacoustic measuring in flows on streamlined obstacles and spectral analysis of statistical characteristics of the velocity and wall-pressure fluctuations in investigating systems. Results. It has been determined experimentally the zones and conditions of vortices formation by various frequency ranges, the extremes of power spectrum densities of the velocity and wall-pressure fluctuations, vortex interaction, ejections and stalls near streamlined surfaces with local obstacles at rather wide Reynolds number ranges. Conclusions. Basing on received space-time characteristics of the velocity and wall-pressure fluctuations and discovered typical features of their spectra the hydromechanical mechanisms of heat and mass exchange and hydroacoustic processes in the investigated systems have been determined. The results of the study can be used for designing of such systems and they reveal the perspective of directed control by mentioned processes for increase of their efficiency.

Physical phenomena occurring in the process of physical–mechanical degumming of fiber from flax straw

The study presents physical phenomena that occur in the physical–mechanical process of degumming of fiber from flax straw. Moreover, the effect of liquid flow through the straw has been determined by analysis of the mass exchange (motion) according to the principles of fluid mechanics. It was shown that conditions of the degumming process, especially the temperature, have a significant effect on acceleration of the mass exchange. The analyses of the results indicated that the developed model laboratory device allowed for evaluation of the mechanism of mass exchange by slow laminar liquid flow. The evaluation of the degumming process with convective mass motion at a higher speed of liquid flow was based on model tests of hydrodynamic washing of three types of gels: fruit pectin, animal gelatin and starch from linen fabrics. It was shown that temperature is a decisive factor affecting the washing out of gels. Better washing out was achieved by using diffusive penetration of water into the gel structure at the initial phase of the process. Using the dynamic washing out of the gels with a water stream of high flow speed (at the m/s range) shortened considerably the washing time.

Heat and Mass Transfer Analysis of Mine Exhaust Air Heat Exchanger

As a good energy resource, Mine exhaust air has an important value of recycling. In this paper, the heat and mass exchange mechanism and potential of the mine exhaust air heat exchanger (MEAHE) is mainly researched. The heat exchanger efficiency is affected by water and air temperature and flow in terms of double efficiency method. The result can provide the basis for the further determine the thermal calculation method for MEAHE, and lays the foundation for the mine comprehensive utilization of waste heat recovery system design.

Early stages of Ostwald ripening

The Becker-Döring (BD) nucleation equation is known to predict a narrow double-exponential front (DEF) in the distribution of growing particles over sizes, which is due to early transient effects. When mass conservation is included, nucleation is eventually exhausted while independent growth is replaced by ripening. Despite the enormous difference in the associated time scales, and the resulting demand on numerics, within the generalized BD model the early DEF is shown to be crucial for the selection of the unique self-similar Lifshitz-Slyozov-Wagner asymptotic regime. Being preserved till the latest stages of growth, the DEF provides a universal part of the initial conditions for the ripening problem, regardless of the mass exchange mechanism between the nucleus and the matrix.