Sweep Gas Flow Rate Research Articles

Quantification of Carbon Dioxide Removal at Low Sweep Gas and Blood Flows

Advancement in oxygenator membrane technology has further expanded the boundaries in the clinical application of extracorporeal carbon dioxide removal (ECCO2R). Despite the advent of modern poly-4-methyl-1-pentene (PMP) membranes, limited information exists on the performance of these membranes at low sweep gas and blood flows. Moreover, physiological relationships for CO2 removal at these flows are less explored. Hence, CO2 removal was quantified in an in vitro setting using a PMP membrane oxygenator. ECCO2R was performed using a .8 m2 surface pediatric oxygenator in an in vitro setting with freshly drawn single-source porcine blood. In this setting, low blood flows of either 200 or 350 mL/min were generated, with sweep gas flow rates of 100, 200, and 400 mL/min, respectively. CO2 transfer ranged from 14.05 ± 4.35 mL/min/m2 to 18.76 ± 4.26 mL/min/m2 at a sweep gas to a blood flow ratio of .5:1 to 2:1 (p < .01). Decreasing this ratio i.e., increasing the blood flow (.5:1.75 and 2:1.75) resulted in a lower CO2 transfer of 10.00 ± 4.77 mL/min/m2 to 16.87 ± 5.09 mL/min/m2, which was still statistically significant (p < .01). Alternatively, decreasing the sweep gas to blood flow ratio, while maintaining a constant gas flow, did not show a significant increase in CO2 extraction (p > .05). At these test parameters, an increase in sweep gas improved the CO2 transfer, whereas an increase in blood flow resulted in a lower CO2 transfer. These results indicate that CO2 removal in low-flow ECCO2R is mainly sweep gas flow driven. Although these settings might not be applicable for clinical use, this study gives tangible information about the important factor involved in ECCO2R.

Reactor scale study of self-heating and self-ignition of torrefied wood in contact with oxygen

This experimental work aims at investigating the potential development of self-heating when torrefied wood chips enter into contact with oxygen. Two kilograms of dried beech chips have been torrefied under nitrogen in a cylindrical reactor at 250 °C or 285 °C. The temperature was then leveled down between 100 °C and 160 °C and nitrogen flow was replaced by oxygen-containing flow. Influences of oxygen volumetric fraction and sweeping gas flow rate were investigated. Temperatures at different bed locations and gaseous product volumetric fractions at the bed output were monitored continuously. In some of the experiments a limited temperature rise was observed while in others a temperature runaway occurred. Thermal considerations indicate a clear enhancement of self-heating propensity with the severity of torrefaction. Gas phase analysis and molecule oxygen balance reveal an adsorption mechanism pathway and a higher rate of oxygen adsorption for the severely torrefied wood. Lowering the oxygen volumetric fraction or increasing the flow rate decrease self-heating behavior and was used to stop self-ignition of the bed.

Techno-economic analysis for CO2 reforming of a medium-grade landfill gas in a membrane reactor for H2 production

In this paper, we report techno-economic analysis for CO2 reforming of a medium-grade landfill gas in a membrane reactor (MR) for a H2 production capacity of 7 m3 h−1 in Korea. Parametric studies for the effect of key operating conditions like a H2 permeance, a H2O sweep gas flow rate, and temperature on the performance in a conventional packed-bed reactor (PBR) and a MR were conducted using Aspen HYSYS®, a commercial process simulator. Based on process simulation studies, economic analysis was carried out to find a unit H2 production cost for both a PBR and a MR. Respective unit H2 production costs of 9.72 and 6.46 $ kgH2−1 were obtained for a PBR and a MR showing about 34% reduction in the MR. Sensitivity analysis was employed to identify key economic factors to determine a unit H2 production cost with labor the most influential factor for both reactors. Probability analysis (PA) was performed with influential factors based on a Monte-Carlo simulation method as uncertainty analysis and a cumulative probability (CP) curve was created for a PBR and a MR under various discount rates from 2 to 10% and key factor ranges from ±10 to ±40%. PA using stochastic approach provided a wide range of a unit H2 production cost coupled with its probability and a critical CP value at which the effect of key factor range on a unit H2 production cost was reversed.

Optimization and characterization of bio-oil produced from cotton shell by flash pyrolysis using artificial neural network

ABSTRACTIn this work, the effects of pyrolysis parameters such as pyrolysis temperature, feedstock particle size, and sweep gas flow rate on the pyrolysis distributions of cotton shell were tested to identify the optimum bio-oil production conditions. The experiments were conducted in a fluidized-bed reactor with nitrogen atmosphere. The efficient Artificial Neural Network (ANN) was used for modeling and optimizing the process parameters. An ANN model was developed based on the back-propagation learning algorithm to predict the effect of parameters. The experimental data acquired are used for training the network. The results showed that the network yields a maximum bio-oil with minimum coefficient of variance (COV) and root mean square values. The results confirmed that the use of an ANN analysis for pyrolysis distribution is quite suitable. Using the ANN technique, the optimal conditions were found to be at the temperature of 450°C, particle size of 0.8 mm, sweep gas flow rate of 1.75 m3/h with 52.2 wt% of bio-oil yield. Furthermore, the liquid product was analyzed for physical, elemental, and chemical composition using Fourier transform infrared (FTIR) spectroscopy and gas chromatography (GC).

Upgrading bio-oil produced from the catalytic pyrolysis of sugarcane (Saccharum officinarum L) straw using calcined dolomite

In this study, the catalytic pyrolysis of sugarcane straw (SCS) into bio-oil and chemicals using calcined dolomite was applied for upgraded bio-oil production. Experiments were performed in a custom-built SS316 tube reactor, and the effects of the pyrolysis parameters, including the different dolomite calcination conditions, temperature (400-600°C), biomass feed rate (0.3–1.2kgh−1), sweeping gas flow rate (80–200cm3min−1) and average size distribution (250–1000µm), were systematically investigated. The results showed that the SCS catalytic pyrolysis process obtained liquid yields of 36.15wt%, gas yields of 52.09wt% and solid yields of 11.76wt% when using a pyrolysis temperature, biomass feed rate, nitrogen sweep gas, and average biomass size of 450°C, 0.6kgh−1, 80cm3min−1 and 500µm, respectively, with 10wt% calcined dolomite. The calcined dolomite influenced the bio-oil components from the carbonylation and the cracking of volatile vapor and resulted in an upgraded bio-oil with a lower oxygen content, higher gross calorific value and decreased acid corrosion.

Techno-economic analysis (TEA) for CO2 reforming of methane in a membrane reactor for simultaneous CO2 utilization and ultra-pure H2 production

Techno-economic analysis (TEA) for CO2 reforming of methane in a membrane reactor (MR) was conducted by using process simulation and economic analysis. Parametric studies for key operating conditions like a H2 permeance, a H2O sweep gas flow rate, operating temperature, and a CO2/CH4 ratio were carried out for a conventional packed-bed reactor (PBR) and a MR using Aspen HYSYS®, a commercial process simulator program and some critical design guidelines for a MR in terms of a H2O sweep gas flow rate and a CO2/CH4 ratio were obtained. Further economic analysis based on process simulation results showed about 42% reduction in a unit H2 production cost in a MR (6.48 $ kgH2−1) than a PBR (11.18 $ kgH2−1) mostly due to the elimination of a pressure swing adsorption (PSA) system in a MR. In addition, sensitivity analysis (SA) revealed that reactant price and labor were the most influential economic factors to determine a unit H2 production cost for both a PBR and a MR. Lastly, profitability analysis (PA) from cumulative cash flow diagram (CCFD) in Korea provided positive net present value (NPV) of $443,760∼$240,980, discounted payback period (DPBP) of 3.03–3.18 y, and present value ratio (PVR) of 7.51–4.97 for discount rates from 2 to 10% showing economic feasibility of the use of a MR as simultaneous CO2 utilization and ultra-pure H2 production.

An upgraded bio-oil produced from sugarcane bagasse via the use of HZSM-5 zeolite catalyst

The pyrolysis upgrading of bio-oil from sugarcane bagasse (SB) using ZSM-5 zeolite catalyst was carried out in a fixed bed reactor to determine the effects of heating rate, temperature, and catalyst/biomass ratio on yield of bio-oil and their chemical compositions. Proximate analysis indicated that SB has 13.2% moisture content. The ultimate analysis carried out established that the percentage of carbon content is higher (48.2%) than oxygen content (44%) while the fibre content analysis showed 26.4% lignin, 33.3% cellulose, 30.1% hemicellulose. The heating rate, temperature and catalyst/biomass ratio were varied in the range of 10–50°C/min, 400–600°C and 0.05–0.25 respectively. The non-catalytic pyrolysis gave the maximum percentage yield (45.67wt%) of bio-oil at a pyrolysis temperature of 600°C, heating rate of 50°C/min, sweeping gas flow rate of 40mL/min and the catalytic pyrolysis gave 40.83wt% of bio-oil at the same conditions. The FT-IR spectra showed that the non-catalytic bio-oil is dominated by oxygenated compounds (acids, ketones, aldehydes, alcohols), while the catalytic bio-oil had preponderances of desirable compounds (alkanes, alkenes, aromatics, phenols). The chemical composition of the bio-oils was analyzed using GC–MS, which revealed that the quality of the bio-oil has been improved using HZSM-5 catalyzed pyrolysis.

Membrane Evaporation for Energy Saving in CO2 Chemical Absorption Process Using a Polybenzimidazole Film: Mass and Heat Transfer

Intensive energy consumption remains a major challenge for the commercial application of CO2 chemical absorption. In this study, a membrane evaporation system based on PBI film was proposed for recovering latent heat from the hot lean CO2 solution in order to reduce the energy penalty during CO2 capture process. The effects of key operational parameters (i.e., evaporation temperature, sweeping gas flow rate, and liquid flow rate) were systematically investigated. It was found that both vapor flux and recovered heat flux had exponential increases when the evaporation temperature increased. Sweeping gas flow rate and liquid flow rate had limited effects on both mass and heat transfer in the membrane evaporation process. The PBI film showed good stability during a 14 days’ duration experiment. Reducing the membrane thickness can significantly improve the membrane evaporation performance. From the viewpoint of energy evaluation, when the evaporation mass reached 10 g/kg solution, the regeneration energy consu...

Impact of membrane lung surface area and blood flow on extracorporeal CO2 removal during severe respiratory acidosis

BackgroundVeno-venous extracorporeal CO2 removal (vv-ECCO2R) is increasingly being used in the setting of acute respiratory failure. Blood flow rates through the device range from 200 ml/min to more than 1500 ml/min, and the membrane surface areas range from 0.35 to 1.3 m2. The present study in an animal model with similar CO2 production as an adult patient was aimed at determining the optimal membrane lung surface area and technical requirements for successful vv-ECCO2R.MethodsFour different membrane lungs, with varying lung surface areas of 0.4, 0.8, 1.0, and 1.3m2 were used to perform vv-ECCO2R in seven anesthetized, mechanically ventilated, pigs with experimentally induced severe respiratory acidosis (pH 7.0–7.1) using a 20Fr double-lumen catheter with a sweep gas flow rate of 8 L/min. During each experiment, the blood flow was increased stepwise from 250 to 1000 ml/min.ResultsAmelioration of severe respiratory acidosis was only feasible when blood flow rates from 750 to 1000 ml/min were used with a membrane lung surface area of at least 0.8 m2. Maximal CO2 elimination was 150.8 ml/min, with pH increasing from 7.01 to 7.30 (blood flow 1000 ml/min; membrane lung 1.3 m2). The membrane lung with a surface of 0.4 m2 allowed a maximum CO2 elimination rate of 71.7 mL/min, which did not result in the normalization of pH, even with a blood flow rate of 1000 ml/min. Also of note, an increase of the surface area above 1.0 m2 did not result in substantially higher CO2 elimination rates. The pressure drop across the oxygenator was considerably lower (<10 mmHg) in the largest membrane lung, whereas the smallest revealed a pressure drop of more than 50 mmHg with 1000 ml blood flow/min.ConclusionsIn this porcine model, vv-ECCO2R was most effective when using blood flow rates ranging between 750 and 1000 ml/min, with a membrane lung surface of at least 0.8 m2. In contrast, low blood flow rates (250–500 ml/min) were not sufficient to completely correct severe respiratory acidosis, irrespective of the surface area of the membrane lung being used. The converse was also true, low surface membrane lungs (0.4 m2) were not capable of completely correcting severe respiratory acidosis across the range of blood flows used in this study.

Highly (h0h)-oriented silicalite-1 membranes for butane isomer separation

Highly (h0h)-oriented silicalite-1 membranes were reproducibly prepared on the inner surface of α-alumina tubes by secondary (seeded) growth of a randomly oriented seed layer. The ideal selectivities of H2/SF6 and N2/SF6 were 2400 and 1500, respectively, indicating that the membrane had few boundary defects. The best silicalite-1 membrane displayed n-butane permeance of 3.1 × 10−7mol (m2sPa)−1 (=926 GPU) and n-butane/i-butane separation factor of 29 for an equimolar n-butane/i-butane binary mixture at 333K. Preferentially oriented and uniform silicalite-1 layers are responsible for the high separation performance. Mixture n-butane/i-butane separation factors were always higher than ideal selectivities. The effects of temperature, pressure, feed concentration, feed flow rate, sweep gas flow rate and water vapor in feed on the membrane performance were studied. The separation mechanisms including preferential adsorption, molecular sieve and competitive diffusion were discussed for the n-butane/i-butane separation through the silicalite-1 membranes.

Mathematical Modelling of Carbon Dioxide Exchange in Hollow Fiber Membrane Oxygenator

The main objective of this study is to simulate the carbon dioxide (CO2) blood-gas exchange in membrane oxygenator, evaluate the effect of sweep gas flow rate on CO2 partial pressure (pCO2) and to determine the response of pCO2 to the step change of sweep gas flow rate. In extension to the simulation of gas transfer in membrane oxygenator, open-loop response on sweep gas flow rate was applied to the developed mathematical model to prove its effect on CO2 removal rate. Three sweep gas flow rates were set, i.e. 1 L/min (Qg/Qb = 0.5), 2 L/min (Qg/Qb = 1) and 4 L/min (Qg/Qb = 2) and the simulated pCO2 in artery was observed. Next, one-way ANOVA test was performed to determine the significant difference in CO2 removal rate between these gas flow rates. For the next test, sweep gas flow rate was changed at t = 60 second and t = 120 second of simulation, to evaluate how pCO2 will response to the step change of gas flow rate. As the result, the highest CO2 removal observed when Qg/Qb = 2, as compared to gas-blood ratio of 1 and 0.5. The ANOVA test also proved the significant difference in simulated pCO2 for each flow rate. For the last test, a proportional response of pCO2 towards the change of sweep gas flow rate was highlighted. In conclusion, the rate of CO2 removal from blood can be manipulated by sweep gas flow rate and this rate can be adjusted to achieve the optimum performance of membrane oxygenator for CO2 sequestration.

Well-dispersed Rh nanoparticles with high activity for the dry reforming of methane

Rh catalysts with low Rh content were prepared by incipient wetness impregnation using [NH4]3[RhCl6]·3H2O or RhCl3·3H2O as precursor salts, on CaO–SiO2 supports. All solids showed a high stability after 48 h on stream for the dry reforming of methane with low carbon content, which made them suitable for obtaining ultrapure hydrogen in a membrane reactor. The methane conversion and hydrogen recovery were measured increasing the sweep gas flow rates to rise the driving force for hydrogen permeation. The catalyst with 0.36 wt.% of Rh showed a slight deactivation. However, the Rh(0.6)/CaO–SiO2 solid, in which the Rh impregnation was performed using [NH4]3[RhCl6]·3H2O, exhibited an increase on CH4 conversion of 77% and a hydrogen recovery equal to 84%.Nanoparticles of about 1.4–1.7 nm surface average diameter were detected for the reduced and used solids indicating that Rh is well dispersed and sintering was not produced after the catalytic tests. Rh particle sizes calculated by CO chemisorption were coincident with those measured by Transmission Electron Microscopy. Characterization by this technique and Laser Raman Spectroscopy of the solids used in membrane reactor revealed the formation of scarce carbon filaments. However, a surface re-oxidation was detected in the low loading catalyst used in the membrane reactor suggesting that it is the main cause for the decrease in the activity of the highly dispersed catalyst.

Hydrogen production, oxygen separation and syngas oxy-combustion inside a water splitting membrane reactor

The present work provides numerical investigations of oxygen permeation, hydrogen generation through water splitting using an oxygen transport membrane and oxy-combustion of syngas. The work involves two models; one for hydrogen generation and oxygen permeation from water splitting, and the other for syngas reaction kinetics. Considering steam dissociation reaction and oxygen permeation process, the hydrogen generation model is developed from oxygen permeation model using user defined function (UDF) that enable the transfer of oxygen across the membrane. The codes were written in C++, then compiled and hooked to the ANSYS Fluent 15.0 software. The investigations revealed that, due to combustion, the syngas reactive flow results in higher oxygen permeation and hydrogen generation rates than the non-reactive case. Effects of various influential parameters such as fuel composition, membrane thickness, operating temperature, sweep gas flow rate and CO2 circulation are investigated in the present study. It was realized that increase in sweep flow rate and inlet temperature results in enhanced oxygen permeation and hydrogen generation rates. Whereas, increase in CO/H2 ratio, membrane thickness and CO2 circulation reduces the amounts of hydrogen and oxygen generated.

Influence of Inorganic Matter in Biomass on the Catalytic Production of Aromatics and Olefins in a Fluidized-Bed Reactor

Catalytic fast pyrolysis (CFP) conversions of sugarcane bagasse (pretreated and untreated, or “raw”) over HZSM-5 zeolite catalyst were conducted in a fluidized-bed reactor to compare the hydrocarbons yields and selectivities of pretreated and raw biomass materials in order to determine the effect of inorganic matter on the aromatics and olefins yields. The effects of reaction temperature and sweeping gas flow rate (SGFR) on aromatics and olefins yields and selectivities were studied. The results showed that a maximum aromatics yield of 12.41% carbon was obtained during CFP of pretreated sugarcane bagasse at an optimum gas flow rate of 2.5 L min–1 and temperature of 500 °C. The highest olefins yield was 10.89% carbon under the same CFP conditions. Benzene and ethylene were the dominant compounds in the aromatics and olefins, respectively. The highest selectivities to benzene and ethylene were 46.44% and 45.45% carbon, respectively. Slightly lower aromatics and olefins yields of 11.77% and 9.9%, respectively, were obtained from CFP of untreated biomass. In the final step, the yields of aromatics and olefins for the raw and treated sugarcane bagasse were compared, and in addition the yields and selectivities at optimum conditions were compared. The results suggest that inorganic matter has an inhibiting effect on hydrocarbons production and also causes catalyst deactivation by blocking the catalyst pores. It is evident that removal of inorganic matter would increase both liquid and hydrocarbons yields during CFP over HZSM-5. Hydrocarbons yields and selectivities were found to depend not only on temperature and SGFR but also on the severity of the treatment process.

Modeling study of oxygen permeation through an electronically short‐circuited YSZ‐based asymmetric hollow fiber membrane

Here, oxygen fluxes through an electronically short‐circuited asymmetric Ag‐YSZ|YSZ|LSM‐YSZ hollow fiber prepared via a combined spinning and sintering route were tested and correlated to an explicit oxygen permeation model. The average oxygen permeation through such asymmetric hollow fiber with a 27 μm‐thick YSZ dense layer reached 0.52 mL (STP) cm−2 min−1 at 1173 K. From the model results, we can obtain the characteristic thickness, the effects of the temperature, and the effect of He sweep gas flow rate to the individual step contribution. The oxygen partial pressure variation in the permeate side, the local oxygen flux, and the three‐different resistance distribution along the axial direction of the asymmetric hollow fiber are theoretically studied; providing guidelines to further improve the membrane performance for oxygen separation. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3491–3500, 2017

Flash Pyrolysis of Lemon Grass (Cymbopogon flexuosus) for Bio-oil Production in an Electrically Heated Fluidized Bed Reactor

Bio-oil, a hopeful substitute as an alternative fuel has gained significant attention due to the predicted shortness of conventional fuels and environmental concern. Bio-oils have attracted a lot of interest, as they are liquid energy carriers and general sources of chemicals. In this study, the pyrolysis characteristics of lemon grass were studied to evaluate their potential use as source of bio-oil. Flash pyrolysis of the lemon grass was carried out on a fluidized bed reactor with nitrogen gas atmosphere. The effects of operating parameters such as temperature, particle size and sweep (nitrogen) gas flow rate were investigated. During this study, the maximum yield of pyrolysis bio-oil 50.6 wt% can be achieved under the operation conditions of 450 °C process temperature, 1.0 mm particle size at sweep gas flow rate of 1.75 m3/h. At the end of the study the bio-oil obtained from the flash pyrolysis was analyzed for physical, elemental and chemical compositions by using Fourier transform infra-red (FTIR) spectroscopy, gas chromatography mass spectroscopy (GC-MS) and 1H NMR spectroscopy.

An experimental study of membranes for capturing water vapor from flue gas

This paper has made an active attempt on recovering water from flue gas using membranes. The properties of SPEEK/PES, a hydrophilic composite hollow fiber membrane, are studied in the present paper using experimental analyses of thermal gravimetric, differential scanning calorimetry and scanning electron micrograph. Experimental results show that SPEEK/PES composite hollow fiber membranes have excellent thermal stability and mechanical properties in flue gas. An experiment with using simulated flue gas (N2/water vapor mixed) is carried out to study the impact of sweep gas flow rate and feed gas temperature on the membrane module properties. The results indicate that the water recovery rate increases with the temperature increasing from 40 °C to 70 °C. The application of capturing the water in flue gas is very attractive, and it will provide a new way of saving energy and alleviating the haze.

Bio-oil production from fast pyrolysis of maple fruit (acer platanoides samaras): product yields

PurposeThe purpose of this paper is to investigate fast pyrolysis of maple fruit as an energy sources. This could serve as a solution to the energy sources problem.Design/methodology/approachFast pyrolysis of maple fruit (samara) was achieved in a fixed bed reactor. The pyrolysis experiments have been conducted on the sample of maple seeds to particularly determine the effects of pyrolysis temperature, particle size and sweep gas flow rate on the pyrolysis product yields.FindingsThe oil of maple fruit from fast pyrolysis has good properties to be a potential candidate as a biofuel or as a source of chemicals. In addition to being environmentally desirable, it can reduce the energy cost, e.g. that Turkey imports a majority of its energy.Originality/valueThe use of maple fruit for fast pyrolysis and pyrolysis conditions impact on the yields of pyrolysis liquid can be considered as novel aspects of this paper.

Characteristic of air separation in hollow-fiber polymeric membrane for oxygen enriched air clean combustion applications

The characteristics of air separation in a hollow-fiber membrane unit are investigated numerically aiming at generation of highly oxygen-enriched air for clean combustion applications. A 2D axisymmetric mesh was generated using Gambit software and, then, was fed to Fluent 12.1 code. Detailed numerical study is presented for air separation using different polymers. Effects of sweep gas flow rate (from zero flow up to 1.15 × 10−7 kg/s), feed gas flow rate (from 3.3 × 10−9 kg/s up to 5.89 × 10−8 kg/s), fed pressure (from 2 atm up to 10 atm) and membrane polymeric material (considering TR-PBO-co-PPL-28 and TR-PI-g-CD) on permeation fluxes and concentrations of O2 and N2 are investigated. Targeting higher exit O2 concentrations, multi-stage air separation unit is developed. The developed unit consists of three stages and the achieved oxygen mass fraction at outlet of first, second and third stages are 0.517, 0.8 and 0.914. Higher stage cut ratio is gained in the third stage as compared to first and second stages.

Effects of membrane structure and operational variables on membrane distillation performance

A bench-scale, sweeping gas, flat-sheet Membrane Distillation (MD) unit was used to assess the importance of membrane architecture and operational variables to distillate production rate. Sweeping gas membrane distillation (SGMD) was simulated for various membrane characteristics (material, pore size, porosity and thickness), spacer dimensions and operating conditions (influent brine temperature, sweep gas flow rate and brine flow rate) based on coupled mass and energy balances. Model calibration was carried out using four membranes that differed in terms of material selection, effective pore size, thickness and porosity. Membrane tortuosity was the lone fitting parameter. Distillate fluxes and temperature profiles from experiments matched simulations over a wide range of operating conditions. Limitations to distillate production were then investigated via simulations, noting implications for MD design and operation. Under the majority of conditions investigated, membrane resistance to mass transport provided the primary limitation to water purification rate. The nominal or effective membrane pore size and the lumped parameter ε/δτ (porosity divided by the product of membrane tortuosity and thickness) were primary determinants of membrane resistance to mass transport. Resistance to Knudsen diffusion dominated membrane resistance at pore diameters <0.3µm. At larger pore sizes, a combination of resistances to intra-pore molecular diffusion and convection across the gas-phase boundary layer determined mass transport resistance. Findings are restricted to the module design flow regimes considered in the modeling effort. Nevertheless, the value of performance simulation to membrane distillation design and operation is well illustrated.