Terms Of Mass Transfer Research Articles

Osmotic, osmovacuum, sonication, and osmosonication pretreatment on the infrared drying of Ginkgo seed slices: Mass transfer, mathematical modeling, drying, and rehydration kinetics and energy consumption.

This study evaluated the mass transfer, drying, and rehydration kinetics (drying and rehydration curve, moisture diffusivity [Deff ]), energy consumption (specific energy consumption [SEC], moisture extraction rate (MER), and specific moisture extraction rate [SMER]), and mathematical modeling of infrared dried Ginkgo biloba seed (GBS) using the various nonthermal pretreatments namely: osmotic (OS), osmovacuum (V + OS), ultrasound (US, ginkgo seed immersed in a distilled water with US), and osmosonication (US + OS, ginkgo seeds immersed in an OS solution with US). Results showed that various pretreatments affected mass transfer, drying, and rehydration characteristics, and energy consumption, which was confirmed by principal component analysis. In terms of mass transfer, US pretreatment recorded the highest weight loss while the osmosonication pretreatment registered the highest solid gain. The entire drying process occurred in the falling-rate period. The Deff values were within the normal range of agroproducts (10-11 to 10-8 m2 /s). The modified Page-I and Weibull model best fitted the drying and rehydration kinetics, respectively, with the coefficient of determination (R2 )>0.991, root mean square error, residual sum of squares, and reduced chi-square closer to zero, compared with the other models. The untreated GBS (control) had the lowest energy efficiency (lowest SMER and MER) and the highest SEC than the pretreated GBS. Among the various pretreatments, the US pretreatment of GBS was superior, with the highest Deff , MER, SMER, and drying rate, and lowest drying time and SEC. Based on the findings, sequential US pretreatment and infrared drying is a feasible drying technique for GBS that could be used commercially. PRACTICAL APPLICATION: Ginkgo tree cultivation in China has exceeded market needs with 60,000 tons per annum of GBS produced. Hence, there is a compelling need to explore new chances to use GBS availability irrespective of the seasonality and address the problem where GBS utilization is limited to the early phases of home-cooked dishes. Although drying increases the shelf life of ginkgo seeds, there is a higher operation cost. Thus, pretreatment can reduce energy consumption and augment the product quality is ideal. This research reported the impact of nonthermal pretreatments on ginkgo seeds' mass transfer, drying, and rehydration characteristics. The present results will provide a comprehensive understanding of the engineering application of ginkgo seed pretreatment, allowing for the best technique to be selected.

A method for simulating interfacial mass transfer on arbitrary meshes

This paper presents a method for modeling interfacial mass transfer in Interface Capturing simulations of two-phase flow with a phase change. The model enables mechanistic prediction of the local rate of the phase change at the vapor–liquid interface on arbitrary computational meshes and is applicable to realistic cases involving two-phase mixtures with large density ratios. The simulation methodology is based on the volume of fluid representation of the flow, whereby an interfacial region in which mass transfer occurs is implicitly identified by a phase indicator, in this case the volume fraction of liquid, which varies from the value pertaining to the “bulk” liquid to the value of the bulk vapor. The novel methodology proposed here has been implemented using the Finite Volume framework and solution methods typical of “industrial” computational fluid dynamics practice. The proposed methodology for capturing mass transfer is applicable to arbitrary meshes without the need to introduce elaborate but artificial smearing of the mass transfer term as is often done in other techniques. The method has been validated via comparison with analytical solutions for planar interface evaporation and bubble growth test cases and against experimental observations of steam bubble growth.

Sensitivity of the Non-Equilibrium Approach for Mixture Condensation to Heat and Mass Transfer Correlations and Thermophysical Properties

Abstract The prediction of mixture condensation is still complex due to the coupled heat and mass transfer and insufficient data of thermophysical mixture properties. This article analyzes the impact of various heat and mass transfer correlations on the non-equilibrium approach for mixture condensation in a vertical plain tube. Furthermore, the influence of thermophysical properties from different databases is investigated. The results are shown for ethanol-water, but allow conclusions to other fluid mixtures. They indicate that the liquid heat transfer coefficient in the non-equilibrium approach dominates the qualitative behavior of the condensation process, but the vapor mass transfer coefficient can only decrease or increase the quantitative level of the effective heat transfer with minor impact. More importantly, the logarithm in the vapor mass transfer term is central for the prediction of the condensation heat transfer. As this logarithm contains vapor-liquid equilibrium (VLE) data, it proves that there is a strong connection between VLE and overall prediction of mixture condensation. A demonstration of available data for thermophysical mixture properties of ethanol-water shows significant deviations, which affect the calculations as well. Besides, data from our own experiments are presented for mixture viscosity of ethanol-water. It is recommended to focus not only on improved heat and mass transfer correlations but also on thermophysical properties and VLE data for a precise prediction of mixture condensation.

Taking a mass-balance approach to assess marine plastics in the South China Sea

The South China Sea (SCS) is recognised as a global hotspot for plastic pollution. We review available field studies and identify a significant lack of data needed to construct a simple mass balance box model for plastic pollution in the SCS. Fundamental information on plastic mass input, transfer and sink terms are simply not available. Also unknown are the rates of accumulation in different environments, the dispersal pathways of plastic particles of different density, the residence times of plastic in the water column and the rate at which macroplastics are transformed into microplastics in different environments. Filling these information gaps is critical for states to determine adequate response measures, including developing and tracking impact of policies to deal with the problem of plastic pollution in the SCS.

Characterization of shale using Helium and Argon at high pressures

In order to estimate the shale gas in place and the eventual recovery during shale gas operations, one of the key requirements is to accurately characterize the shale's petrophysical and transport properties such as porosity, permeability, diffusivity, and storage capacity. Despite the many efforts reported in the technical literature aiming to provide an improved understanding of the complex pore structures and the associated fluid flow in gas shales, a complete characterization of organic-rich shale samples still poses a big challenge. In this work, we have characterized mass transfer and sorption in shale at different length scales using Helium (He) and Argon (Ar) as probe gases. Thermogravimetric analysis (TGA) with a shale cube of ~1 cm3 in size and gas expansion experiments with a full-diameter core (3.5” in diameter) were used to measure sorption kinetics/isotherms and mass transfer, respectively. Both samples are from the same depth/location in the Marcellus shale formation. The TGA steady-state technique was initially used to generate excess sorption isotherms for Ar, while dynamic TGA experiments were used to study its sorption kinetics. The TGA experiments demonstrate that Ar, which has a similar sorption potential as Methane, but is generally assumed to be inert, adsorbs onto the surfaces of the mesoporous and microporous regions of the shale samples according to a Langmuir-type behavior. Helium expansion experiments, on the full-diameter core, were used to measure the overall porosity, on the basis that He is a non-sorbing and inert gas as compared to Ar. The He expansion experiments, furthermore, allow us to delineate the mass transfer of gas across the inherent hierarchy of pore sizes, including macropores (macro- and micro-cracks), mesopores and micropores. Similar expansion experiments were also performed with Ar to study the combined impact of mass transfer and sorption. A triple-porosity model (TPM) was utilized to interpret the He expansion experiments with the shale core and to extract (estimate) relevant transport parameters. We report and compare here the diffusivities and permeabilities of the whole core for both He and Ar, as calculated from the modeling and fitting of the experimental data. On the premise that the shale cube is representative of the matrix region of the core, the Ar sorption kinetics from the cube experiments were subsequently combined with the transport parameters extracted from the He experiments to predict the behavior of the Ar expansion test with the full-diameter core. An excellent agreement is observed between the model predictions and the experimental data. The experimental observations and their interpretation indicate that one must be cautious when using Ar to estimate the true porosity and permeability of shales. In addition, we demonstrate that He and Ar probe gases, when used in tandem, can be employed effectively as a tool to characterize shales in terms of mass transfer and sorption dynamics across scales.

Impact of a wall downstream of an air curtain nozzle on air curtain separation efficiency

Air curtains (ACs) employ plane turbulent jets to separate two environments in terms of heat and mass transfer, while still allowing unrestricted access through the opening between these environments. Most previous studies focused on ACs discharged from nozzles located just above the opening. However, in some cases ACs have to be installed close to the ceiling at a substantial distance from the top of the opening. The AC blown downwards along the vertical wall then first resembles a wall jet and after reaching the top of the opening starts resembling a free jet. The present study analyzes the behavior and performance of an AC with upstream wall above the opening. 2D steady RANS CFD simulations are performed based on grid-sensitivity analyses and validation with experimental data for a wall jet and a free jet. The total opening height is 4 m and vertical walls of 0.5 m, 1 m and 2 m, partly closing this opening, are considered. AC performance is evaluated both with the separation efficiency η (based on infiltration) and the adapted separation efficiency η* (based on infiltration and exfiltration). It is shown that the presence of the wall reduces jet decay. The longer the wall, the larger the jet momentum over the opening height. This reduces infiltration and increases η, but it increases exfiltration and therefore decreases η*. In practice, the jet discharge velocity (jet momentum) will have to be adjusted to keep high η*.

Theoretical aspects of electrochemistry at low temperature

• Theoretical models of heterogeneous electron transfer can predict electrochemical responses at low temperature. • Kinetic and thermodynamic data can be extracted from various electrochemical methods at low temperature. • Chemically-coupled electron-transfer reactions can be better investigated by using low-temperature electrochemistry. This paper aims at providing theoretical basis on electrochemical processes performed at low temperature ( T ) according to three different aspects. First, the effect of T -decrease is treated in terms of thermodynamics, mass-transfer, and kinetics of electron transfer (ET) heterogeneous reactions. In particular, predictions of ET kinetics at low temperature are discussed in the frame of Marcus-Hush’s model. The second part is focused on the changes associated to temperature decrease for different electrochemical methods including cyclic voltammetry (CV), chronoamperometry (CA), AC Impedance (ACI) and AC voltammetry (ACV). This section gives keys to extract electrochemical data from low- T experimental curves. In the third part, theoretical aspects of low- T cyclic voltammetry for multiple or chemically-coupled electron-transfer reactions are discussed. CVs of typical molecular mechanisms (EE, EC, ECE…) are provided in order to better visualize the impact of temperature on the redox behavior.

Thermal radiation, chemical reaction, Hall and ion slip effects on MHD oscillatory rotating flow of micro-polar liquid

The thermal radiation, chemical reaction, Hall and ion slip impacts on double-diffusive unsteady MHD natural convective rotating flow of micro-polar fluid past a semi-infinite vertical moving porous plate under the influence of uniform transverse magnetic field with convective boundary conditions have been investigated. The entire system is assumed to fluctuate in time with invariant frequency, therefore, the solutions of the boundary layer be of the oscillatory style. The non-dimensional governing equations are solved analytically through perturbation method and discussed computationally with references to pertinent parameters. It is observed that the velocity and micro-rotation profiles increases with an increase in Hall and ion slip parameters but reverse effects are found with an increasing in viscosity ratio and chemical reaction parameter. The thermal radiation parameter is to increase the temperature profiles but reverse effect is observed with an increasing in frequency of oscillations. Further, the concentration is decreased with increase in the Schmidt number and, it is increased with increase in the chemical reaction parameter. For engineering curiosity, the local skin friction and couple stress coefficients, rate of heat and mass transfer in terms of Nusselt number and Sherwood number are obtained analytically and discussed numerically. Although it is originated that, the local Nusselt number and local Sherwood number remains constant with varying all pertinent parameters. The heat and mass transfer on MHD flows through porous media with the chemical reaction arise in many transport processes both naturally and artificially in many branches of science and engineering applications. This phenomenon plays an important role in the chemical industry, power and cooling industry for drying, chemical vapour deposition on surfaces, cooling of nuclear reactors, and petroleum industries. The Hall and ion slip effects are used in many situations in bio-medical engineering and aero-space engineering.

Three-dimensional magnetized slip flow of Carreau non-Newtonian fluid flow through conduction and radiative chemical reaction

An electrically conducting three-dimensional non-Newtonian Carreau fluid induced by bidirectional movement of sheet is demonstrated in this work. The aspects of viscous heating, radiation and first-order chemical reactions are executed in energy transport and mass species expressions. The new variables are defined to restructure the mathematical problem into single independent variable equations (ordinary differential equations, ODE’s). The re-framed ODE’s are exploited numerically through the utilization of MATLAB bvp4c package. The derived results of velocities, temperature and species distributions are executed graphically and interpreted physically for both shear-thinning and shear-thickening cases. Also, the numerical results for coefficients of skin friction, rate of mass transfer in terms of Sherwood number and rate of heat transfer in terms of Nusselt number are presented in tables. The influence of local Weissenberg numbers on Sherwood and Nusselt numbers for shear-thinning fluids is reversed to shear-thickening fluids. The thermal radiation parameter enhances the fluid temperature, and chemical reaction parameter decelerates the fluid concentration.

Influence of Aeration Microporous Aperture on Oxygen Mass Transfer Efficiency in Terms of Bubble Motion Flow Field

Microporous aeration has been widely used to restore eutrophic water bodies. The gas–liquid mass transfer in the aeration process has a significant influence on the improvement of water quality. Therefore, the influence mechanism of oxygen mass transfer is worth studying. However, the influence of bubble movement characteristics on oxygen mass transfer has not been systematically studied. Thus, the present study explored the influence mechanism of microporous apertures on oxygen mass transfer in terms of bubble motion characteristics by investigating the oxygen mass transfer process and the feature of bubble movement under different aeration microporous aperture sizes. The results showed that the mass transfer efficiency was reduced as the micropore aperture increased from 200 to 400 μm. and the reduction rate was 7.17% when the aperture increased from 200 to 300 μm, which was lower than that from 300 to 400 μm (19.17%). Furthermore, the micropore aperture showed a positive correlation with the time-averaged velocity field. With the increase in aperture, the bubble velocity gradient (from the center to both sides of the edge) increased from about 0.2 to 0.4 m/s, which increased the oxygen mass transfer effect. The increase of micropore aperture caused the increase of average Sauter bubble diameter and the decrease of specific surface area of bubbles. In addition, the negative effects of the reduction of specific surface area and the shortening of bubble residence time on oxygen mass transfer efficiency were greater than the positive effects of the increase of turbulent kinetic energy. When the aperture changes from 300 to 400 μm, the shortening of bubble residence time should have played a major role. This study provides some theoretical parameters for investigating the mechanism of oxygen mass transfer in microporous aeration.

Cementation of Copper on Zinc in Agitated Vessels Equipped with Perforated Baffles as Turbulence Promoters

In this work, the possibility of intensifying the cementation process in stirred vessels was studied by using the perforated baffles as turbulence promoters; the cementation reaction of Cu+2 on Zn was selected as a model. Zn was used in the form of a sheet lining the inner wall of an agitated vessel. Parameters considered are initial concentration of Cu+2, solution temperature, impeller rotation speed, and impeller geometry. Within the present range of parameters studied, the rate of cementation was found to increase with increasing initial concentration of Cu+2, solution temperature, and impeller rotation speed. At the same rotational speed, a flat turbine gave a higher rate of cementation than a 45° pitched turbine. The present suggested that baffles’ geometry gave superior performance in terms of mass transfer of copper cementation compared to the conventional baffle geometry. All parameters that affect the rate of cementation were correlated in the form of dimensionless equations suitable for the design and performance prediction of the agitated vessel. Potential applications of the obtained results in the field of hydrometallurgical processes and wastewater treatment were discussed.

Influence of non-local diffusion in avascular tumour growth

The availability and evolution of chemical agents play an important role in the growth of a tumour and, therefore, the mathematical description of their consumption is of special interest. Usually, Fick’s law of diffusion is adopted for describing the local character of the evolution of chemicals. However, in a highly complex, heterogeneous medium, as is a tumour, the progression of chemical species could be influenced by non-local interactions. In this respect, our goal is to investigate the influence of such types of diffusion on the growth of a tumour in the avascular stage. For our purposes, we consider a diffusion equation for the evolution of the chemical agents that accounts for the existence of non-local interactions in a non-Fickean manner, and that involves notions of fractional calculus. In particular, the introduction of derivatives or integrals of fractional type of order has proven to be an effective mathematical tool in the description of various non-local phenomena. To achieve our goals, we adopt part of the modelling assumptions outlined in previous works, in which the growth of a tumour is described in terms of mass transfer among the tumour’s constituents and structural changes that occur in the tumour itself in response to growth. The latter ones are characterised by means of the Bilby–Kröner–Lee decomposition of the deformation gradient tensor. We perform numerical simulations, whose results indicate the relevance of embracing a fractional framework in modelling tumour growth. Specifically, the real parameter ‘dominates’ the way in which the tumour grows, since it permits the modelling of a variety of growth patterns ranging from the standard growth to no growth at all.

Mercury Removal from Aqueous Solution Using ETS-4 in the Presence of Cations of Distinct Sizes

The removal of the hazardous Hg2+ from aqueous solutions was studied by ion exchange using titanosilicate in sodium form (Na-ETS-4). Isothermal batch experiments at fixed pH were performed to measure equilibrium and kinetic data, considering two very distinct situations to assess the influence of competition effects: (i) the counter ions initially in solution are Na+ and Hg2+ (both are exchangeable); (ii) the initial counter ions in solution are tetrapropylammonium (TPA+) and Hg2+ (only Hg2+ is exchangeable, since TPA+ is larger than the ETS-4 micropores). The results confirmed that ETS-4 is highly selective for Hg2+, with more than 90% of the mercury being exchanged from the fluid phase. The final equilibrium attained under the presence of TPA+ or Na+ in solution was very similar, however, the Hg2+/Na+/ETS-4 system in the presence of Na+ required more 100 h to reach equilibrium than in the presence of TPA+. The Hg2+/Na+/ETS-4 system was modelled and analyzed in terms of equilibrium (mass action law) and mass transfer (Maxwell–Stefan (MS) formalism). Concerning equilibrium, no major deviations from ideality were found in the range of studied concentrations. On the other hand, the MS based model described successfully (average deviation of 5.81%) all kinetic curves of mercury removal.

Simulation on vapor-liquid equilibrium of CO2-[emim][Tf2N] in flow state and depressurization of its refrigeration cycle based on Aspen Plus

To investigate the depressurization mechanism of the CO 2 vapor compression refrigeration cycle with an ionic liquid loop, a vapor-liquid equilibrium (VLE) model of CO 2 -[emim][Tf 2 N] in the flow state was established based on Aspen Plus, and the prediction of VLE in the supercritical state was carried out. Furthermore, the effects of CO 2 inlet pressure, absorber temperature, CO 2 inlet mole fraction and CO 2 inlet flow rate on the depressurization amplitude of absorber were analyzed through the absorption-desorption process simulation. The results showed that with the increase of CO 2 inlet pressure in the supercritical state, the depressurization amplitude increased but its growth rate slowed down, which indicated that the effect of pressure as a driving term of mass transfer decreased in the supercritical state. The depressurization amplitude decreased with the increase of absorber temperature, and decreased rapidly with the increase of CO 2 inlet mole fraction. In this sense, adding an auxiliary desorber at the absorber inlet is beneficial to the system depressurization. Due to the limited absorption capacity of quantitative [emim][Tf 2 N] in the absorber, with the continuous increase of CO 2 inlet flow rate, the depressurization amplitude first dropped sharply, then flattened, and later dropped rapidly. Because the CO 2 flow rate in an actual system is proportional to the system cooling capacity, the proper mass flow ratio of CO 2 -[emim][Tf 2 N] should be selected to reconcile the cooling capacity and depressurization amplitude.

Experimental and numerical investigation of catalytic PM combustion in a fluidized bed type PM removal device for low-temperature continuous regeneration

A fluidized bed filter can perform highly efficient PM collection and low-temperature continuous regeneration. However, to further reduce continuous regeneration temperature, a rough surface bed particle was selected herein. It is expected that the rough surface increases and stabilizes doped catalyst on bed particle even in fluidized bed. This bed particle can stably support 9.48 g-catalyst/kg-bed particle of doped catalyst versus 1.58 g-catalyst/kg-bed particle in previous research. This increase in catalyst amount increases the probability of good PM-catalyst contact, and collection efficiency can easily maintain its initial value due to catalytic PM combustion. PM combustion also depends on fluidization. Thus, combustion kinetics in a fluidized bed was investigated via a newly developed thermogravimetric analyzer that considered PM-gas relative velocity, and a constructed kinetic model was applied to numerical simulation. PM combustion obeyed an Arrhenius relationship, and the effect of PM-gas relative velocity was included in the kinetic model as a mass transfer term. A continuous regeneration experiment was conducted under optimal conditions, and the continuous regeneration temperature is 330 °C. As water vapor occurs in combustor exhaust, we added 10 vol% water vapor and found that the continuous regeneration is further reduced to 300 °C.

The human impact on North American erosion, sediment transfer, and storage in a geologic context

Humans are primary agents of geomorphic change, and rates of anthropogenic landscape change likely far exceed the pace of change expected from natural geologic processes. Nevertheless, our understanding of the impact of humans on the natural landscape is limited by difficulties in accurately comparing past and present rates of change across wide spatial and temporal scales. Here, we present a compilation of >4000 rates of alluvial sediment accumulation that provide an indirect record of North American erosion, mass transfer and sediment storage from the late Pleistocene to the present day. Continent-wide rates of alluvium accumulation were broadly stable for ~40,000 years, but increased 10-fold during the rapid expansion of agriculture and river system modification associated with European colonization. Interpreted in terms of mass transfer, humans have moved as much sediment in North America in the past century as natural processes can transfer in 700–3000 years.

Air curtain performance: Introducing the adapted separation efficiency

Air curtains (ACs) are plane turbulent impinging jets that are used to separate two environments in terms of heat and mass transfer while still allowing traffic between these environments. The many applications of ACs across a wide variety of industries makes the evaluation of their performance an important but difficult task. The aim of this paper is to introduce a performance indicator, called the adapted separation efficiency, that is suitable for different types of systems that may involve different AC configurations (downward blowing, upward blowing, lateral blowing, multiple jets, etc.) at multiple scales, different transported quantities (heat, water vapor, particles, gases, etc.) subjected to various transport mechanisms (advection, molecular and turbulent diffusion) and varying environmental conditions (gradients in environmental pressure and/or density). It is defined using a conventional efficiency formula. The principle of this performance indicator is illustrated with a generic case study where the performance is evaluated for two basic AC configurations involving cross-jet pressure and density gradients, as well as different jet momentum fluxes. The case study is conducted based on computational fluid dynamics employing validated large eddy simulations.

Modeling and assessment of the transfer effectiveness in integrated bioreactor with membrane separation

Abstract Integrating a reaction process with membrane separation allows for effective product removal, favorable shifting of the reaction equilibrium, overcoming eventual inhibitory or toxic effects of the products and has the advantage of being energy and space saving. It has found a range of applications in innovative biotechnologies, generating value-added products (exopolysaccharides, antioxidants, carboxylic acids) with high potential for separation/ concentration of thermosensitive bioactive compounds, preserving their biological activity and reducing the amount of solvents and the energy for solvent recovery. Evaluating the effectiveness of such integrated systems is based on fluid dynamics and mass transfer knowledge of flowing matter close to the membrane surface – shear deformation rates and shear stress at the membrane interface, mass transfer coefficients. A Computational Fluid Dynamics (CFD)-based approach for assessing the effectiveness of integrated stirred tank bioreactor with submerged membrane module is compiled. It is related to the hydrodynamic optimization of the selected reactor configuration in two-phase flow, as well as to the concentration profiles and analysis of the reactor conditions in terms of reaction kinetics and mass transfer.

Bubble diameter distribution and intergroup mass transfer coefficient in flows with phase change

The intergroup mass transfer term is investigated in the multigroup two-fluid model. Past intergroup mass transfer modeling is thoroughly reviewed, highlighting the limited applicability to phase-change flows due to the closure need of the intergroup mass transfer coefficient. The intergroup mass transfer coefficient is dependent on the bubble diameter distribution. The backward transform method, which is used to transform chord length distribution data to a bubble diameter distribution, is improved with a new regularization strategy which can better reduce the inherent instability of the inverse problem. Experimental data from phase-change flows are processed with the modified backward transform method to evaluate the bubble distribution and to determine the intergroup mass transfer coefficient. Analytical correlations for the intergroup mass transfer coefficient are developed, employing the Nukiyama-Tanasawa distribution function and the Rosin-Rammler distribution function. The benchmark with the experimental data demonstrates that the new correlations for the intergroup mass transfer coefficient are accurate over a wide range of two-phase flow conditions. In addition, a new empirical correlation for the intergroup mass transfer coefficient is developed from a regression of the experimental data.

Mathematical modeling of organic liquid dissolution in heterogeneous source zones

A simple one-dimensional heterogeneous-source model was used to simulate dissolution of organic liquid that was non-uniformly distributed in physically heterogeneous porous media. The permeability field was depicted as a pseudo-homogeneous medium. The source zone was discretized into multiple domains representing different organic-liquid configurations and hydraulic accessibilities, each with a different representative upscaled mass transfer rate coefficient that is temporally variable. This simplified approach represents a system where minimal information is available regarding system heterogeneities. All factors that influence dissolution were incorporated into the calibrated mass transfer terms. The mass transfer terms were calibrated for each zone separately. The one-dimensional, heterogeneous-source model adequately simulated the multi-stage dissolution behavior observed for column-scale systems that were packed with different natural soils, as well as for flow-cell systems wherein the source zone consisted of both a residual zone and pool. The results indicate that the model adequately simulated the presence of multiple organic-liquid zones in porous media with different configurations and hydraulic accessibilities, which accounts for the non-ideal dissolution behavior observed. The calibrated mass transfer terms for each source type were consistent with those obtained for systems that contained only one of either source type.