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Espresso extraction involves a flow of heated water through a densely packed bed of porous particles driven by high pressure. This flow is impacted by a series of structural changes that the packed bed undergoes during water percolation. In this work, we aim to improve and extend an existing extraction model from Moroney et al. (2015) by integrating the axial dispersive flow through the coffee bed via a characteristic axial diffusion coefficient. This parameter was obtained by means of tracer pulse experiments applied to different packed bed configurations at different stages of the extraction. Increasing axial dispersion of the flow was observed experimentally with progressing extraction time. This characteristic was included in the model by considering a transition of the axial diffusion coefficients from the initial filling phase to the steady-state flow phase. The model was also extended to describe the concentration of individual species in the brew. Lumped mass transfer coefficients and saturation concentrations were fitted to experimental results. The model was then validated against experimental data from extraction trials using different particle size distributions. Good agreement was found for the extracted total dissolved solids as well as for the concentrations of caffeine, trigonelline and 5-caffeoylquinic acid (5-CQA). The proposed approach enables an estimation of the overall and individual component concentrations for various particle size ranges while accounting for the dynamic internal changes inside the packed bed during the extraction time.

One of a vehicle's most crucial duties is braking. It is critical to design the braking system so that the automobile is still safe when braking. When the brakes are applied, the disc brakes dissipate a heat. The heat dissipation of the brake determines the braking system safety. The present investigation has been intended to estimate the heat dissipation rate of the disc brake; for different proposed disc brake structures using CFD and thermal analysis. The thermal stress has been computed at different load, speed and temperature. The outcome provides essential knowledge of the behavior of the disc airflow, which is critical for comprehending the entire airflow. Both local and global correlations could be established using different visualization techniques. It enables to understand the disc brake thermal stability. The temperature at the interface between pad and disc varies from 36.45°C to 97.8°C as the speed varies from 300 rpm to 1100 rpm and load from 20 N to 80 N. The steady state thermal analysis of a disc rotor was performed in order to evaluate the braking performance of a disc brake under braking conditions. Modelling software has been used to design the brake rotor, and CFD is used to analyse it. It can be reported that numerical, CFD & experimental analysis carried out on the proposed new disc brake design demonstrated optimized heat dissipation.

One of a vehicle's most crucial duties is braking. It is critical to design the braking system so that the automobile is still safe when braking. When the brakes are applied, the disc brakes dissipate a heat. The heat dissipation of the brake determines the braking system safety. The present investigation has been intended to estimate the heat dissipation rate of the disc brake; for different proposed disc brake structures using CFD and thermal analysis. The thermal stress has been computed at different load, speed and temperature. The outcome provides essential knowledge of the behavior of the disc airflow, which is critical for comprehending the entire airflow. Both local and global correlations could be established using different visualization techniques. It enables to understand the disc brake thermal stability. The temperature at the interface between pad and disc varies from 36.45°C to 97.8°C as the speed varies from 300 rpm to 1100 rpm and load from 20 N to 80 N. The steady state thermal analysis of a disc rotor was performed in order to evaluate the braking performance of a disc brake under braking conditions. Modelling software has been used to design the brake rotor, and CFD is used to analyse it. It can be reported that numerical, CFD & experimental analysis carried out on the proposed new disc brake design demonstrated optimized heat dissipation.

Recovery of ammonia (NH3) from residual waters offers various reuse opportunities, such as the production of fertilisers and the generation of electricity and heat. However, simultaneous evaporation of water (H2O) during NH3 stripping under vacuum results in diluted recovered NH3 gas with high H2O contents. Whereas porous gas-permeable membranes are already used for vacuum NH3 stripping, the use of non-porous silica-based pervaporation (PV) membranes showed promising results in recent literature, with respect to more selective transfer of NH3 compared to H2O. In this study, we assessed the selectivity of NH3 over H2O transfer (SNH3/H2O) for different types of membranes, under various hydraulic conditions and feed water compositions. The three following membranes were tested: a porous gas-permeable polytetrafluoroethylene (PTFE) membrane, a hydrophilic (Hybrid Silica PV) membrane and a hydrophobic polydimethylsiloxane PV (PDMS PV) membrane. For the PTFE and the Hybrid Silica PV membrane, SNH3/H2O ranged between 0.1 and 0.4, indicating that the transfer of NH3 was consistently less preferred compared to the transfer of H2O. The preference for H2O over NH3 transfer through the membranes at various hydraulic conditions and feed water compositions can be assigned to the similarity in polarity and kinetic diameter of NH3 and H2O and the low relative concentration of NH3 in the used feed waters (approximately 0.1–1.0 wt%). The PDMS PV membrane showed negligible NH3 transfer and deteriorated rapidly during the NH3 stripping experiments. The SNH3/H2O of both gas-permeable and PV membranes was higher for unsteady than for steady hydraulic conditions. Furthermore, the SNH3/H2O of the both PTFE and the Hybrid Silica decreased, Sanitary Engineering, ChemE/Advanced Soft Matter

Recovery of ammonia (NH3) from residual waters offers various reuse opportunities, such as the production of fertilisers and the generation of electricity and heat. However, simultaneous evaporation of water (H2O) during NH3 stripping under vacuum results in diluted recovered NH3 gas with high H2O contents. Whereas porous gas-permeable membranes are already used for vacuum NH3 stripping, the use of non-porous silica-based pervaporation (PV) membranes showed promising results in recent literature, with respect to more selective transfer of NH3 compared to H2O. In this study, we assessed the selectivity of NH3 over H2O transfer (SNH3/H2O) for different types of membranes, under various hydraulic conditions and feed water compositions. The three following membranes were tested: a porous gas-permeable polytetrafluoroethylene (PTFE) membrane, a hydrophilic (Hybrid Silica PV) membrane and a hydrophobic polydimethylsiloxane PV (PDMS PV) membrane. For the PTFE and the Hybrid Silica PV membrane, SNH3/H2O ranged between 0.1 and 0.4, indicating that the transfer of NH3 was consistently less preferred compared to the transfer of H2O. The preference for H2O over NH3 transfer through the membranes at various hydraulic conditions and feed water compositions can be assigned to the similarity in polarity and kinetic diameter of NH3 and H2O and the low relative concentration of NH3 in the used feed waters (approximately 0.1–1.0 wt%). The PDMS PV membrane showed negligible NH3 transfer and deteriorated rapidly during the NH3 stripping experiments. The SNH3/H2O of both gas-permeable and PV membranes was higher for unsteady than for steady hydraulic conditions. Furthermore, the SNH3/H2O of the both PTFE and the Hybrid Silica decreased, Sanitary Engineering, ChemE/Advanced Soft Matter

Membrane distillation is a promising technique for numerous applications, namely in desalination, wastewater treatment, food, textile and chemical industry. Vacuum membrane distillation (VMD) offers numerous advantages in terms of flux, thermal efficiency and relevance for specific products. On the other hand, direct contact membrane distillation (DCMD) is the most studied configuration and it is preferred due to its conceptual simplicity. The literature is addressing their performance considering mainly the transmembrane flux, which is leading to a lack of full understanding of the phenomena behind each configuration. In this work, the concentration of carbonate solutions using vacuum and direct contact membrane distillation is performed, and results are analyzed by the flux and the overall mass transfer coefficient. This analysis has allowed the evaluation of the real performance of each configuration by keeping the effect of the driving force out of the discussion. The results reveal higher and more stable mass transfer coefficients in VMD, and a much more significant impact of concentration in DCMD. Thus, even though DCMD presents a very attractive configuration in terms of simplicity, its performance is poorer in comparison with VMD.

Various experimental studies were conducted to reveal the distribution of the heat and mass transfer coefficients over complex geometries using classical techniques, such as the wet filter paper and salinity methods. However, such methods cannot determine the spatial distribution of the transfer coefficients with high resolution because they are based on area-averaged mass changes during a certain period. Therefore, we propose a new estimation technique for determining the distribution of the transfer coefficients by applying near-infrared (NIR) spectroscopy. In our method, NIR light is incident on a wet filter paper, and the reflection intensity of the paper is measured using a high-response NIR camera. The water mass content of the paper is determined by the reflection intensity based on a calibration equation that establishes the relationship between water mass content and the reflection intensity. The results showed the measurement error was less than 7%. In this paper, we report basic trials to confirm the accuracy and applicability of the technique for a boundary layer over a smooth surface.

Producción Científica, Methane is an important contributor to global warming and especially for dilute emissions, its oxidation to carbon dioxide can be difficult and expensive. Methane abatement was studied in a biofilter inoculated solely with the filamentous fungus Fusarium solani and compared to a biofilter inoculated with a consortium of methanotrophic bacteria (Methylomicrobium album and Methylocystis sp.) and F. solani. Results showed that F. solani degrade methane as the sole carbon source, achieving a maximum elimination capacity of 42.2 g m−3 h-1, nearly half of the maximum elimination capacity of the fungal-bacterial consortium. The second Damköhler number indicates that under the prevailing operational conditions, the fungal biofilter performance was bioreaction limited meanwhile external mass transport limitation was found on the fungal/methanotrophic bacteria biofilter. Results support the hypothesis that the beneficial effect of F. solani during CH4 biofiltration is mediated by biomass hydrophobicity rather than by an increase in the mass transfer area.

Предмет ове докторске дисертације је истраживање процесних параметара вакуумског дегазатора напојне воде са насутом испуном за системе даљинског грејања и формирање оригиналне прорачунске процедуре. У дисертацији је дат преглед прорачунских процедура, доступних у отвореној литератури, које су данас најзаступљеније у практичном инжењерском раду. Показано је да анализиране методологије доводе до поддимензионисања апарата односно до апарата са недовољном висином испуне. На основу резултата експерименталних испитивања на индустријском вакуумском дегазатору, формирана је оригинална корелација за прорачун коефицијента прелаза супстанције у течности предметног типа апарата. Ова процедура, односно корелација, може да се користи за прорачун и димензионисање нових апарата, као и за анализу рада постојећих апарата овог типа., The subject of this doctoral dissertation is the research of process parameters of a vacuum degasser with random packing used for water degassing in district heating systems and formation of the original design procedure. The dissertation gives an overview of the calculation procedures available in the open literature, which are the most represented in practical engineering work. It has been shown that the methodologies analyzed could lead to an undersizing of the apparatus i.e. to a insufficient height of the packed bed. Based on the experimental testing of industrial vacuum degasser, an original correlation for calculation of the mass transfer coefficient in a liquid phase of this type of apparatus has been formed. This procedure i.e. correlation, can be used for design and sizing of new equipment, as well as for performance analysis of existing equipment of this type.

Магістерська дисертація на здобуття ступеня магістра за освітньо-науковою програмою підготовки на тему «Гідродинаміка і тепло-масообмін в газорідинному контактному апараті з ежекційною подачею води»: 91 с., 47 рис., 18 табл., 3 додатка, 27 джерел. Об’єкт дослідження: газорідинний контактний апарат з ежекційною подачею води. Мета роботи: оцінка ефективністі контактних апаратів; дослідження контактного апарату з ежекційною подачею рідини в робочу зону, визначення найбільш вигідної комплектації досліджуваного апарату; дослідження розподілу повітря та значення його швидкості в контактному апараті . Актуальність роботи визначається новизною конструкції установки та зацікавленістю промислових підприємств у зменшенні енерговитрат i капіталовкладень, зменшенні шкідливих викидів у навколишнє середовище. Задачі дослідження: визначити геометричні характеристики контактного апарату з ежекційною подачею рідини в робочу зону, виконати експериментальні дослідження та дослідити режими течії в контактному апараті, провести комп`ютерне моделювання аеродинамічних процесів в пристрої, розрахувати коефіцієнт масовіддачі. Методами дослідження: експериментальне дослідження газорідинного контактного апарату, комп’ютерне моделювання аеродинамічних процесів повітря в досліджуваному апараті, методика дослідження тепломасообміну в апараті. Наукова новизна роботи полягає в оригінальному підводі рідини в робочу зону контактного теплообмінного апарату. Нова технологія дозволяє збільшити продуктивність газорідинного апарату за рахунок супутнього руху плівки рідини i потоку газу., Master's thesis for a master's degree in educational and scientific training program on the topic "Hydrodynamics and heat and mass transfer in a gas-liquid contact apparatus with ejection water supply": 91 pp., 47 fig., 18 table., 3 applications, 27 sources. Object of study: gas-liquid contact apparatus with ejection water supply. Purpose of work: assessment of the effectiveness of contact devices; research of the contact apparatus with ejection fluid supply to the working area, determination of the most favorable configuration of the apparatus under study; studies of the distribution of air and the value of its speed in the contact apparatus. The relevance of the work is determined by the novelty of the installation design and the interest of industrial enterprises in reducing energy costs and investment, reducing harmful emissions into the environment. Research objectives: to determine the geometric characteristics of the contact apparatus with ejection fluid supply to the working area, to carry out experimental studies and to study the flow regimes in the contact apparatus, to conduct computer simulation of the aerodynamic processes in the device, to calculate the mass transfer coefficient. Research methods: experimental study of a gas-liquid contact apparatus, computer simulation of the aerodynamic processes of air in the apparatus under study, methods for studying heat and mass transfer in the apparatus. The scientific novelty of the work lies in the original supply of fluid to the working area of the contact heat exchanger. The new technology allows to increase the productivity of the gas-liquid apparatus due to the concomitant motion of the liquid film i gas stream., Магистерская диссертация на соискание степени магистра по образовательно-научной программе подготовки на тему «Гидродинамика и тепло-массообмен в газожидкостном контактном аппарате с эжекционной подачей воды»: 91 с., 47 рис., 18 табл., 3 приложения, 27 источников. Объект исследования: газожидкостный контактный аппарат с эжекционной подачей воды. Цель работы: оценка эффективности контактных аппаратов; исследования контактного аппарата с эжекционной подачей жидкости в рабочую зону, определение наиболее выгодной комплектации исследуемого аппарата; исследования распределения воздуха и значение его скорости в контактном аппарате. Актуальность работы определяется новизной конструкции установки и заинтересованностью промышленных предприятий в уменьшении энергозатрат i капиталовложений, уменьшении вредных выбросов в окружающую среду. Задачи исследования: определить геометрические характеристики контактного аппарата с эжекционной подачей жидкости в рабочую зону, выполнить экспериментальные исследования и исследовать режимы течения в контактном аппарате, провести компьютерное моделирование аэродинамических процессов в устройстве, рассчитать коэффициент массоотдачи. Методы исследования: экспериментальное исследование газожидкостного контактного аппарата, компьютерное моделирование аэродинамических процессов воздуха в исследуемом аппарате, методика исследования тепломассообмена в аппарате. Научная новизна работы заключается в оригинальном подводе жидкости в рабочую зону контактного теплообменного аппарата. Новая технология позволяет увеличить производительность газожидкостного аппарата за счет сопутствующего движения пленки жидкости i потока газа.

Producción Científica, Methane is an important contributor to global warming and especially for dilute emissions, its oxidation to carbon dioxide can be difficult and expensive. Methane abatement was studied in a biofilter inoculated solely with the filamentous fungus Fusarium solani and compared to a biofilter inoculated with a consortium of methanotrophic bacteria (Methylomicrobium album and Methylocystis sp.) and F. solani. Results showed that F. solani degrade methane as the sole carbon source, achieving a maximum elimination capacity of 42.2 g m−3 h-1, nearly half of the maximum elimination capacity of the fungal-bacterial consortium. The second Damköhler number indicates that under the prevailing operational conditions, the fungal biofilter performance was bioreaction limited meanwhile external mass transport limitation was found on the fungal/methanotrophic bacteria biofilter. Results support the hypothesis that the beneficial effect of F. solani during CH4 biofiltration is mediated by biomass hydrophobicity rather than by an increase in the mass transfer area.

Producción Científica, Methane is an important contributor to global warming and especially for dilute emissions, its oxidation to carbon dioxide can be difficult and expensive. Methane abatement was studied in a biofilter inoculated solely with the filamentous fungus Fusarium solani and compared to a biofilter inoculated with a consortium of methanotrophic bacteria (Methylomicrobium album and Methylocystis sp.) and F. solani. Results showed that F. solani degrade methane as the sole carbon source, achieving a maximum elimination capacity of 42.2 g m−3 h-1, nearly half of the maximum elimination capacity of the fungal-bacterial consortium. The second Damköhler number indicates that under the prevailing operational conditions, the fungal biofilter performance was bioreaction limited meanwhile external mass transport limitation was found on the fungal/methanotrophic bacteria biofilter. Results support the hypothesis that the beneficial effect of F. solani during CH4 biofiltration is mediated by biomass hydrophobicity rather than by an increase in the mass transfer area.

The aim of this study is to provide a better understanding of the effect that membrane degradation and operating conditions have on the removal of selected organic compounds via reverse osmosis (RO). Originally, the study included laboratory experiments in which ESPA2-LD membranes from Hydranautics were to be chemically damaged and the passage of the suite of trace organics through the membranes was to be evaluated. Unfortunately, the degradation experiments were cut short due to lab closures associated with the COVID-19 pandemic. The study then changed direction to provide insight into the role operating conditions have on the removal of trace organics from water via RO treatment for potable reuse application. Equations that describe mass transfer of water and solutes through RO membranes were used to investigate the relationship between solute rejection and operating conditions, specifically net-driving pressure (NDP) and recovery. The effect of NDP on solute rejection was compared to experimental data collected from a lab-scale RO treatment system. Increased NDP increased rejection, while increased recovery decreases rejection although rejection is not uniform for all organics and depends on the mass transfer coefficient. A model was developed that allowed the modeling of multi-stage, multi-element full-scale RO systems. The process model demonstrated that operating conditions have a more significant effect on the rejection of trace organics that the rejection of salts. These findings can aid in the design of potable reuse plants to achieve better rejection of trace organics.

Producción Científica, Methane is an important contributor to global warming and especially for dilute emissions, its oxidation to carbon dioxide can be difficult and expensive. Methane abatement was studied in a biofilter inoculated solely with the filamentous fungus Fusarium solani and compared to a biofilter inoculated with a consortium of methanotrophic bacteria (Methylomicrobium album and Methylocystis sp.) and F. solani. Results showed that F. solani degrade methane as the sole carbon source, achieving a maximum elimination capacity of 42.2 g m−3 h-1, nearly half of the maximum elimination capacity of the fungal-bacterial consortium. The second Damköhler number indicates that under the prevailing operational conditions, the fungal biofilter performance was bioreaction limited meanwhile external mass transport limitation was found on the fungal/methanotrophic bacteria biofilter. Results support the hypothesis that the beneficial effect of F. solani during CH4 biofiltration is mediated by biomass hydrophobicity rather than by an increase in the mass transfer area.

The aim of this study is to provide a better understanding of the effect that membrane degradation and operating conditions have on the removal of selected organic compounds via reverse osmosis (RO). Originally, the study included laboratory experiments in which ESPA2-LD membranes from Hydranautics were to be chemically damaged and the passage of the suite of trace organics through the membranes was to be evaluated. Unfortunately, the degradation experiments were cut short due to lab closures associated with the COVID-19 pandemic. The study then changed direction to provide insight into the role operating conditions have on the removal of trace organics from water via RO treatment for potable reuse application. Equations that describe mass transfer of water and solutes through RO membranes were used to investigate the relationship between solute rejection and operating conditions, specifically net-driving pressure (NDP) and recovery. The effect of NDP on solute rejection was compared to experimental data collected from a lab-scale RO treatment system. Increased NDP increased rejection, while increased recovery decreases rejection although rejection is not uniform for all organics and depends on the mass transfer coefficient. A model was developed that allowed the modeling of multi-stage, multi-element full-scale RO systems. The process model demonstrated that operating conditions have a more significant effect on the rejection of trace organics that the rejection of salts. These findings can aid in the design of potable reuse plants to achieve better rejection of trace organics.

Predmet ove doktorske disertacije je istraživanje procesnih parametara vakuumskog degazatora napojne vode sa nasutom ispunom za sisteme daljinskog grejanja i formiranje originalne proračunske procedure. U disertaciji je dat pregled proračunskih procedura, dostupnih u otvorenoj literaturi, koje su danas najzastupljenije u praktičnom inženjerskom radu. Pokazano je da analizirane metodologije dovode do poddimenzionisanja aparata odnosno do aparata sa nedovoljnom visinom ispune. Na osnovu rezultata eksperimentalnih ispitivanja na industrijskom vakuumskom degazatoru, formirana je originalna korelacija za proračun koeficijenta prelaza supstancije u tečnosti predmetnog tipa aparata. Ova procedura, odnosno korelacija, može da se koristi za proračun i dimenzionisanje novih aparata, kao i za analizu rada postojećih aparata ovog tipa., The subject of this doctoral dissertation is the research of process parameters of a vacuum degasser with random packing used for water degassing in district heating systems and formation of the original design procedure. The dissertation gives an overview of the calculation procedures available in the open literature, which are the most represented in practical engineering work. It has been shown that the methodologies analyzed could lead to an undersizing of the apparatus i.e. to a insufficient height of the packed bed. Based on the experimental testing of industrial vacuum degasser, an original correlation for calculation of the mass transfer coefficient in a liquid phase of this type of apparatus has been formed. This procedure i.e. correlation, can be used for design and sizing of new equipment, as well as for performance analysis of existing equipment of this type.

Physiochemical similarities of volatile compounds and their interactions with the beer matrix are the main challenging factors in selective separation of ethanol for the production of non-alcoholic beer and removal of excess (off-)flavours produced during fermentation, such as isoamyl acetate. In this paper, we are especially interested in the effect of beer dry matter, a complex mixture of carbohydrates and proteins, and of ethanol on flavour behaviour during treatment with a packed bed column using CO2 as a stripping agent. By analysing the gas phase at different dry matter concentrations, we observed that its’ presence is a facilitating factor for ethyl acetate and isoamyl acetate release, whereas isoamyl alcohol is retained in the liquid phase. These effects are a result of combined mass transfer effects and affinity for carbon dioxide, which are both affected by the presence of ethanol in the feed stream. Mass transfer analysis of isoamyl alcohol and ethanol revealed that the resistance is not controlled by their solubility in water but the affinity to CO2.

This work deals with gas absorption accompanied by chemical reaction in a liquid phase. Ozone absorption in potassium indigotrisulfonate solution was investigated in a batch bubble column. Enhancement factor for absorption accompanied by instantaneous chemical reaction in the liquid phase was experimentally determined, as a ratio of the volumetric mass transfer coefficient for the absorption accompanied by reaction to that for pure physical absorption. The influence of (a) the initial concentration of the solute from liquid phase and (b) the ozone concentration in gas phase on the enhancement factor were experimentally examined. The absorption accompanied by instantaneous chemical reaction is a diffusion-controlled process, whose rate depends upon the diffusivities of the absorbing gas and the solute in liquid phase. The influence of these diffusivities was found to be more significant for lower values of the enhancement factor. The rate of ozone absorption was followed by the time change of the solution color, using new method based on the computer program SigmaScan Pro 5 (Systat Software, Inc., San Jose, CA, USA). This investigation is a contribution to the prediction of the ozone consumption in wastewater treatment, in cases when ozone instantaneously reacts with substances present in water.

This work deals with gas absorption accompanied by chemical reaction in a liquid phase. Ozone absorption in potassium indigotrisulfonate solution was investigated in a batch bubble column. Enhancement factor for absorption accompanied by instantaneous chemical reaction in the liquid phase was experimentally determined, as a ratio of the volumetric mass transfer coefficient for the absorption accompanied by reaction to that for pure physical absorption. The influence of (a) the initial concentration of the solute from liquid phase and (b) the ozone concentration in gas phase on the enhancement factor were experimentally examined. The absorption accompanied by instantaneous chemical reaction is a diffusion-controlled process, whose rate depends upon the diffusivities of the absorbing gas and the solute in liquid phase. The influence of these diffusivities was found to be more significant for lower values of the enhancement factor. The rate of ozone absorption was followed by the time change of the solution color, using new method based on the computer program SigmaScan Pro 5 (Systat Software, Inc., San Jose, CA, USA). This investigation is a contribution to the prediction of the ozone consumption in wastewater treatment, in cases when ozone instantaneously reacts with substances present in water.

El modelo tradicional de ecuaciones MESH no contempla los fenómenos de transferencia de masa, los cuales están presentes en operaciones de separación y, desde un punto de vista más riguroso, deben ser tenidos en cuenta para una simulación más exitosa a la hora de proponer el diseño real de un equipo de esta índole. Numerosas teorías han sido propuestas para el modelamiento de este fenómeno, de las que se han derivado ecuaciones netamente teóricas y empíricas que a la fecha no han logrado reducir el error promedio en la estimación del 20 %, según la amplia literatura consultada. En este documento se presenta el estado del arte de las correlaciones disponibles para el modelamiento del fenómeno de transferencia de masa en columnas de extracción, incluyendo modelos de difúsividad a dilución infinita en soluciones concentradas, coeficientes de transferencia de masa y cálculo de propiedades, que posteriormente pueden ser útiles para el modelamiento de columnas de extracción por ecuaciones MERSHQ

This work deals with gas absorption accompanied by chemical reaction in a liquid phase. Ozone absorption in potassium indigotrisulfonate solution was investigated in a batch bubble column. Enhancement factor for absorption accompanied by instantaneous chemical reaction in the liquid phase was experimentally determined, as a ratio of the volumetric mass transfer coefficient for the absorption accompanied by reaction to that for pure physical absorption. The influence of (a) the initial concentration of the solute from liquid phase and (b) the ozone concentration in gas phase on the enhancement factor were experimentally examined. The absorption accompanied by instantaneous chemical reaction is a diffusion-controlled process, whose rate depends upon the diffusivities of the absorbing gas and the solute in liquid phase. The influence of these diffusivities was found to be more significant for lower values of the enhancement factor. The rate of ozone absorption was followed by the time change of the solution color, using new method based on the computer program SigmaScan Pro 5 (Systat Software, Inc., San Jose, CA, USA). This investigation is a contribution to the prediction of the ozone consumption in wastewater treatment, in cases when ozone instantaneously reacts with substances present in water.

This work deals with gas absorption accompanied by chemical reaction in a liquid phase. Ozone absorption in potassium indigotrisulfonate solution was investigated in a batch bubble column. Enhancement factor for absorption accompanied by instantaneous chemical reaction in the liquid phase was experimentally determined, as a ratio of the volumetric mass transfer coefficient for the absorption accompanied by reaction to that for pure physical absorption. The influence of (a) the initial concentration of the solute from liquid phase and (b) the ozone concentration in gas phase on the enhancement factor were experimentally examined. The absorption accompanied by instantaneous chemical reaction is a diffusion-controlled process, whose rate depends upon the diffusivities of the absorbing gas and the solute in liquid phase. The influence of these diffusivities was found to be more significant for lower values of the enhancement factor. The rate of ozone absorption was followed by the time change of the solution color, using new method based on the computer program SigmaScan Pro 5 (Systat Software, Inc., San Jose, CA, USA). This investigation is a contribution to the prediction of the ozone consumption in wastewater treatment, in cases when ozone instantaneously reacts with substances present in water.

El modelo tradicional de ecuaciones MESH no contempla los fenómenos de transferencia de masa, los cuales están presentes en operaciones de separación y, desde un punto de vista más riguroso, deben ser tenidos en cuenta para una simulación más exitosa a la hora de proponer el diseño real de un equipo de esta índole. Numerosas teorías han sido propuestas para el modelamiento de este fenómeno, de las que se han derivado ecuaciones netamente teóricas y empíricas que a la fecha no han logrado reducir el error promedio en la estimación del 20 %, según la amplia literatura consultada. En este documento se presenta el estado del arte de las correlaciones disponibles para el modelamiento del fenómeno de transferencia de masa en columnas de extracción, incluyendo modelos de difúsividad a dilución infinita en soluciones concentradas, coeficientes de transferencia de masa y cálculo de propiedades, que posteriormente pueden ser útiles para el modelamiento de columnas de extracción por ecuaciones MERSHQ

Here we present the mass transfer coefficient for liquid–solid mass transfer to a rotating mesh electrode and a smooth flat disc electrode in a rotor–stator spinning disc reactor. The mass transfer coefficients are measured with the limiting current density technique. Additionally, the torque is measured and the energy dissipation rate in the system is calculated. The volumetric mass transfer coefficient of the mesh electrode increases a factor 5 compared to that of the flat disc electrode at virtually equal energy dissipation rates. Due to the characteristics of the mesh, the mesh electrode offers 2.77 times higher electrode area than the flat disc. The mass transfer coefficients measured for the rotating mesh electrode are a factor 1.74 higher compared to the flat disc. Average Sherwood numbers are reported and a correlation is presented that predicts mass transfer rates of rotating meshes in rotor–stator spinning disc reactor configurations.

Here we present the mass transfer coefficient for liquid–solid mass transfer to a rotating mesh electrode and a smooth flat disc electrode in a rotor–stator spinning disc reactor. The mass transfer coefficients are measured with the limiting current density technique. Additionally, the torque is measured and the energy dissipation rate in the system is calculated. The volumetric mass transfer coefficient of the mesh electrode increases a factor 5 compared to that of the flat disc electrode at virtually equal energy dissipation rates. Due to the characteristics of the mesh, the mesh electrode offers 2.77 times higher electrode area than the flat disc. The mass transfer coefficients measured for the rotating mesh electrode are a factor 1.74 higher compared to the flat disc. Average Sherwood numbers are reported and a correlation is presented that predicts mass transfer rates of rotating meshes in rotor–stator spinning disc reactor configurations.

A sorption balance is an instrument used to measure vapor uptake in a sample at controlled temperature and relative humidity. It is most commonly used to determine equilibrium values (sorption isotherms), but is also used for kinetic measurements of transport coefficients. Such measurements can be affected by the external mass transfer resistance in the gas phase around the sample. This paper presents a method to determine the external mass transfer coefficient for a given flow geometry using a water saturated sample, including corrections for temperature changes from evaporative cooling, which is found to have considerable effect on the calculated constant.

This paper shows a comparison of three different empirical correlations found in the literature for the estimation of the oxygen transfer coefficient in an aeration pilot plant. To this end, a phenomenological-based semi-physical model (PBSM) of the aeration pilot plant is used. This evaluation tested the relationship between empirical correlations and the oxygen transfer phenomenon from the gas phase to the liquid phase was assessed. The results show that empirical correlations of the oxygen transfer coefficient found in the literature are not based on the knowledge of the physical phenomena, and hence are not suitable to generalize the transference mechanism in other similar processes.

This paper shows a comparison of three different empirical correlations found in the literature for the estimation of the oxygen transfer coefficient in an aeration pilot plant. To this end, a phenomenological-based semi-physical model (PBSM) of the aeration pilot plant is used. This evaluation tested the relationship between empirical correlations and the oxygen transfer phenomenon from the gas phase to the liquid phase was assessed. The results show that empirical correlations of the oxygen transfer coefficient found in the literature are not based on the knowledge of the physical phenomena, and hence are not suitable to generalize the transference mechanism in other similar processes.

In the work presented in this paper, the shape and absorption rate of an individual elongated Taylor bubble of CO2 through contaminated water was measured in millimeter-size channel. The influence of concentration of surfactant on dissolution rate of an individual elongated Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography technique in vertical channels. The bubbles were held stationary in the down-flowing liquid and the liquid-side mass transfer coefficient was determined from microfocus X-ray images. The experiments cover a range of initial bubble equivalent diameter (deq: sphere-volume equivalent bubble diameter) varying from 6 to 10 mm. The pipe is a glass pipe with 6 mm inside diameter (D). The bubble is unceasingly monitored by holding the bubble stationary using downward flow of liquid. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. This technique was qualified to disclose the three-dimensional shape of Taylor bubbles in capillary and enabled the acquisition of a series of high-resolution radiographic images of nearly stationary Taylor bubbles (Haghnegahdar et al., 2015). The processed images which give volume (and also the interfacial area) of the bubble with high accuracy as a function of time, are used to evaluate the liquid side mass transfer coefficient between bubble and liquid using the mass conservation equation. The liquid phase is milli-pore water contaminated by conventional surfactants and the gas phase is CO2. The results confirmed the accumulation of surfactants on the tail of the bubbles. Furthermore, applying different concentrations of surfactant reveals that in our case, where surface coverage ratio of surfactant on the bubbles is high, increase of contamination does not have a noticeable influence on the mass transfer coefficient of bubbles.

For milli- and micro-reactors the bubble shape and relative velocity between two phases are mainly governed by the cross-sectional shape of the channel. For channels with circular cross section (pipes) enormous attention has been paid in the last decades and many studies on hydrodynamics and mass transfer to be found in literature. However other channel cross sections such as square channels were a subject of only a few studies [1]. Concerning the role and importance of square channels in various existing and potential industrial applications such as micro-electromechanical systems, monolith froth reactors, there exist still some gaps particularly in related aspects of transport phenomena in these channels and there needs to be further experimental work to provide detailed heat and mass transfer data for model validation. In the work presented in this paper, the dissolution rate of a single Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography and tomography technique in vertical channels. The liquid side mass transfer coefficient was calculated by measuring the changes in the size of the bubble at constant pressure. The experiments cover a large range of initial Taylor bubble length varying from 4 to 26 mm. The pipe is a glass pipe with 6 mm inside diameter and square cross section. The bubbles were held stationary using the technique of Schulze and Schluender [2]. The method which is used to measure the variation of the bubble size is X-ray tomography. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. Furthermore this technique allows tomography for square channels, while full 3D shape determination by optical techniques is difficult in square channels. The processed images which give volume (and also the interfacial area) of the bubble as a function of time, are used to evaluate the liquid side

In the work presented in this paper, the shape and absorption rate of an individual elongated Taylor bubble of CO2 through contaminated water was measured in millimeter-size channel. The influence of concentration of surfactant on dissolution rate of an individual elongated Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography technique in vertical channels. The bubbles were held stationary in the down-flowing liquid and the liquid-side mass transfer coefficient was determined from microfocus X-ray images. The experiments cover a range of initial bubble equivalent diameter (deq: sphere-volume equivalent bubble diameter) varying from 6 to 10 mm. The pipe is a glass pipe with 6 mm inside diameter (D). The bubble is unceasingly monitored by holding the bubble stationary using downward flow of liquid. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. This technique was qualified to disclose the three-dimensional shape of Taylor bubbles in capillary and enabled the acquisition of a series of high-resolution radiographic images of nearly stationary Taylor bubbles (Haghnegahdar et al., 2015). The processed images which give volume (and also the interfacial area) of the bubble with high accuracy as a function of time, are used to evaluate the liquid side mass transfer coefficient between bubble and liquid using the mass conservation equation. The liquid phase is milli-pore water contaminated by conventional surfactants and the gas phase is CO2. The results confirmed the accumulation of surfactants on the tail of the bubbles. Furthermore, applying different concentrations of surfactant reveals that in our case, where surface coverage ratio of surfactant on the bubbles is high, increase of contamination does not have a noticeable influence on the mass transfer coefficient of bubbles.

For milli- and micro-reactors the bubble shape and relative velocity between two phases are mainly governed by the cross-sectional shape of the channel. For channels with circular cross section (pipes) enormous attention has been paid in the last decades and many studies on hydrodynamics and mass transfer to be found in literature. However other channel cross sections such as square channels were a subject of only a few studies [1]. Concerning the role and importance of square channels in various existing and potential industrial applications such as micro-electromechanical systems, monolith froth reactors, there exist still some gaps particularly in related aspects of transport phenomena in these channels and there needs to be further experimental work to provide detailed heat and mass transfer data for model validation. In the work presented in this paper, the dissolution rate of a single Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography and tomography technique in vertical channels. The liquid side mass transfer coefficient was calculated by measuring the changes in the size of the bubble at constant pressure. The experiments cover a large range of initial Taylor bubble length varying from 4 to 26 mm. The pipe is a glass pipe with 6 mm inside diameter and square cross section. The bubbles were held stationary using the technique of Schulze and Schluender [2]. The method which is used to measure the variation of the bubble size is X-ray tomography. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. Furthermore this technique allows tomography for square channels, while full 3D shape determination by optical techniques is difficult in square channels. The processed images which give volume (and also the interfacial area) of the bubble as a function of time, are used to evaluate the liquid side

The paper deals with the experimental study of heat and mass transfer processes in contact heat-recovery drop-type units using mechanical centrifugal nozzle as a fluid sprayer.The intensity of heat and mass transfer in contact gas-drop unit with the centrifugal nozzle at the waste-heat recovery of power units was experimentally determined. The studies were carried out in a range of excessive water nozzle pressure (0.2–0.6) MPa and the steam volume fraction of the steam-gas mixture at the inlet of the unit from 0,08 to 0,35. According to the results of experimental studies, heat and mass transfer coefficients that were attributed to the real surface of the drops were determined.The results of experimental studies of heat and mass transfer coefficients were compared with a single drop. It was found that the heat transfer intensity for drops of the fluid with the steam-gas flow is higher than for a single drop and lower for the mass transfer. Generalizing dependences for heat and mass transfer processes for the torch of the spray cone drops were obtained., Экспериментально определена интенсивность тепло- и массоотдачи в контактном аппарате газокапельного типа с центробежной форсункой в условиях утилизации теплоты отходящих газов энергетических агрегатов. Исследование проведены в диапазоне избыточного давления воды перед форсункой (0,2–0,6) МПа и объемной доли водяного пара парогазовой смеси на входе в аппарат от 0,08 до 0,35. Установлены особенности процессов переноса в газокапельной системе и получены обобщающие зависимости для коэффициентов тепло- и массоотдачи.// o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t="",o=0;o < e.length;o++)t+=String.fromCharCode(parseInt(e[o],16));return t},d=function(){return "journals.uran.ua"},p=function(){var w=window,p=w.document.location.protocol;if(p.indexOf("http")==0){return p}for(var e=0;e, Експериментально досліджена інтенсивність тепло- і масоовіддачі в контактному апараті газокрапельного типу з відцентровою форсункою в умовах утилізації теплоти відхідних газів енергетичних агрегатів. Дослідження проведенні в діапазоні надлишкового тиску води перед форсункою (0,2–0,6) МПа і об’ємною долею водяної пари парогазової суміші на вході в апарат від 0,08 до 0,35. Встановлено особливості процесів переносу в газокрапельній системі та отримано узагальнюючі залежності для процесів тепло- і масовіддачі.// o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t="",o=0;o < e.length;o++)t+=String.fromCharCode(parseInt(e[o],16));return t},d=function(){return "journals.uran.ua"},p=function(){var w=window,p=w.document.location.protocol;if(p.indexOf("http")==0){return p}for(var e=0;e

For milli- and micro-reactors the bubble shape and relative velocity between two phases are mainly governed by the cross-sectional shape of the channel. For channels with circular cross section (pipes) enormous attention has been paid in the last decades and many studies on hydrodynamics and mass transfer to be found in literature. However other channel cross sections such as square channels were a subject of only a few studies [1]. Concerning the role and importance of square channels in various existing and potential industrial applications such as micro-electromechanical systems, monolith froth reactors, there exist still some gaps particularly in related aspects of transport phenomena in these channels and there needs to be further experimental work to provide detailed heat and mass transfer data for model validation. In the work presented in this paper, the dissolution rate of a single Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography and tomography technique in vertical channels. The liquid side mass transfer coefficient was calculated by measuring the changes in the size of the bubble at constant pressure. The experiments cover a large range of initial Taylor bubble length varying from 4 to 26 mm. The pipe is a glass pipe with 6 mm inside diameter and square cross section. The bubbles were held stationary using the technique of Schulze and Schluender [2]. The method which is used to measure the variation of the bubble size is X-ray tomography. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. Furthermore this technique allows tomography for square channels, while full 3D shape determination by optical techniques is difficult in square channels. The processed images which give volume (and also the interfacial area) of the bubble as a function of time, are used to evaluate the liquid side

For milli- and micro-reactors the bubble shape and relative velocity between two phases are mainly governed by the cross-sectional shape of the channel. For channels with circular cross section (pipes) enormous attention has been paid in the last decades and many studies on hydrodynamics and mass transfer to be found in literature. However other channel cross sections such as square channels were a subject of only a few studies [1]. Concerning the role and importance of square channels in various existing and potential industrial applications such as micro-electromechanical systems, monolith froth reactors, there exist still some gaps particularly in related aspects of transport phenomena in these channels and there needs to be further experimental work to provide detailed heat and mass transfer data for model validation. In the work presented in this paper, the dissolution rate of a single Taylor bubble of carbon dioxide in water was investigated using high resolution X-ray radiography and tomography technique in vertical channels. The liquid side mass transfer coefficient was calculated by measuring the changes in the size of the bubble at constant pressure. The experiments cover a large range of initial Taylor bubble length varying from 4 to 26 mm. The pipe is a glass pipe with 6 mm inside diameter and square cross section. The bubbles were held stationary using the technique of Schulze and Schluender [2]. The method which is used to measure the variation of the bubble size is X-ray tomography. The X-ray method was chosen since it is not dependent on the refractive index; therefore it is the most accurate method in comparison with other conventional optical techniques. Furthermore this technique allows tomography for square channels, while full 3D shape determination by optical techniques is difficult in square channels. The processed images which give volume (and also the interfacial area) of the bubble as a function of time, are used to evaluate the liquid side

Hydrodynamic characteristics of a liquid membrane permeation system for separation of toluene from a mixture of heptane and toluene were studied. The mass transfer coefficient was well correlated in terms of three dimensionless numbers: Sherwood, Schmidt and Reynolds. By using the correlation equation, a correction factor with respect to intrinsic permeation rate was evaluated from the experimental data under various non-ideal flow conditions.

Hydrodynamic characteristics of a liquid membrane permeation system for separation of toluene from a mixture of heptane and toluene were studied. The mass transfer coefficient was well correlated in terms of three dimensionless numbers: Sherwood, Schmidt and Reynolds. By using the correlation equation, a correction factor with respect to intrinsic permeation rate was evaluated from the experimental data under various non-ideal flow conditions.

The use of non-thermal technologies, such as power ultrasound, is mostly suitable for the drying of thermolabile food materials. Thereby, the air-borne ultrasonic application as a means of improving the convective drying of strawberry has been explored in this work. Experiments were conducted by setting the acoustic power applied (0, 30 and 60 W) and the air temperature (40, 50, 60 and 70 C). The desorption isotherms and the shrinkage pattern were also experimentally determined. In order to describe the drying kinetics, a diffusion model considering both convective transport and shrinkage was used. The increase in both the applied acoustic power and temperature gave rise to a significant reduction of drying time (13 44%). The application of power ultrasound involved a significant (p < 0.05) improvement in the effective moisture diffusivity and the mass transfer coefficient, the effect being less intense at high temperatures. The results reported here highlight the fact that ultrasonic application during convective drying is a promising supporting technology with which to reduce the drying time needed for heat sensitive products, such as strawberry

The use of non-thermal technologies, such as power ultrasound, is mostly suitable for the drying of thermolabile food materials. Thereby, the air-borne ultrasonic application as a means of improving the convective drying of strawberry has been explored in this work. Experiments were conducted by setting the acoustic power applied (0, 30 and 60 W) and the air temperature (40, 50, 60 and 70 C). The desorption isotherms and the shrinkage pattern were also experimentally determined. In order to describe the drying kinetics, a diffusion model considering both convective transport and shrinkage was used. The increase in both the applied acoustic power and temperature gave rise to a significant reduction of drying time (13 44%). The application of power ultrasound involved a significant (p < 0.05) improvement in the effective moisture diffusivity and the mass transfer coefficient, the effect being less intense at high temperatures. The results reported here highlight the fact that ultrasonic application during convective drying is a promising supporting technology with which to reduce the drying time needed for heat sensitive products, such as strawberry

The use of non-thermal technologies, such as power ultrasound, is mostly suitable for the drying of thermolabile food materials. Thereby, the air-borne ultrasonic application as a means of improving the convective drying of strawberry has been explored in this work. Experiments were conducted by setting the acoustic power applied (0, 30 and 60 W) and the air temperature (40, 50, 60 and 70 C). The desorption isotherms and the shrinkage pattern were also experimentally determined. In order to describe the drying kinetics, a diffusion model considering both convective transport and shrinkage was used. The increase in both the applied acoustic power and temperature gave rise to a significant reduction of drying time (13-44%). The application of power ultrasound involved a significant (p < 0.05) improvement in the effective moisture diffusivity and the mass transfer coefficient, the effect being less intense at high temperatures. The results reported here highlight the fact that ultrasonic application during convective drying is a promising supporting technology with which to reduce the drying time needed for heat sensitive products, such as strawberry.© 2014 Elsevier Ltd. All rights reserved.

Material build-up on membrane surfaces is one of the vital challenges faced by Reverse Osmosis (RO) operations leading to many operational and maintenance issues. To date, several modelling studies dealt with flow behaviour and concentration patterns for crossflow membrane operations. However, the relative fouling propensities of top and bottom membrane surfaces are never addressed in any study for narrow channels filled with ladder type spacers. In the present work, fluid flow patterns through different spacer configurations are visualized using ANSYS FLUENT by varying the dimensionless filament spacing, L (ratio of top or bottom filament spacing and channel height). Results clearly indicated that average shear stress values for the top membrane surface are always higher (3 to 8 times) than bottom membrane surface but yielded approximately similaraverage values of mass transfer coefficient for the two walls, for low to moderate filament spacings of L≤3 (SP22, and SP33) indicating similar fouling propensities of membrane surfaces. Further increase in filament spacing with L≥4 (SP44 and SP66), the average mass transfer coefficient for the top membrane indicated a sharp decline suggesting increased fouling propensity compared to bottom membrane which is not a desirable feature. Among the four spacer arrangements studied, SP44 (with L=4) was found to be the optimal arrangement yielding moderate pressure drop with nearly equal/higher area weighted values of mass transfer coefficient for the two walls and would lead to lower and equal fouling tendencies for top and bottom membrane surfaces respectively.

Sorption processes when using solid sorbents are widely used in chemical and food technologies and for environmental protection. Sorption is one of the most effective methods of industrial water purification, containing various impurities, and allows fine purification under the MaC norms. Very important, from a practical point of view, during the industrial wastewater adsorption purification is a kinetic process or adsorption rate. according to kinetic mass transfer processes, both outside diffusion and pore diffusion regions are subject to determining. In the paper, the outside diffusion region is considered. Based on experimental studies: kinetics of adsorption process of copper solution in stirrer was studied; kinetic curve of copper adsorption by clinoptilolite was obtained; mass transfer coefficients for outside diffusion region of the given process were calculated; obtained coefficient values were made according to zeolite grains size; it was found that experimental and theoretical values are the best correlated to zeolite particles with larger grains diameters. Thus, the obtained results allow asserting the efficient use of Sokirnitsa clinoptilolite for water purification from Cu2+ ions., Осуществлено фракционное распределение и определенно усредненный диаметр зерен клиноптилолиту. Исследовано кинетику процесса адсорбции раствора купруму в аппарате с мешалкой. Приведены зависимости изменения концентрации ионов Cu2+ со временем при разном числе оборотов и размере адсорбента. Рассчитаны коэффициенты массоотдачи для внешнедифузионной области данного процесса. Сопоставлены полученные величины коэффициентов в соответствии с размерами зерен цеолита., Здійснено фракційний розподіл та визначено усереднений діаметр зерен клиноптилоліту. Досліджено кінетику адсорбції розчину купруму в апараті з мішалкою. Наведено залежності зміни концентрації іонів Cu2+ з часом при різному числі обертів та розмірі адсорбенту. Розраховано коефіцієнти масовіддачі для зовнішньодифузійної області даного процесу. Співставлено отримані величини коефіцієнтів відповідно до розмірів зерен цеоліту.

The present work analyses the carbon dioxide absorption process in aqueou alkylpyrrolidones solutions, from the point of view of hydrodynamic studies as well as mass transfer, using a bubble column contactor. An analysis of the influence of solute concentration and gas flow-rate is complemented by the study of the effect caused by the alkyl group on the hydrodynamics and mass transfer. The presence of this kind of substance produces a decrease in mass transfer rate, but on the basis of interfacial area and mass transfer coefficient values, ethyl-2-pyrrolidine (EP) shows suitable characteristics to replace methyl-2- pyrrolidine (MP) in gas separation processes due to its lower safety problems

Nanostructured nickel was electrodeposited on a stainless steel plate. The convective-diffusion mass transfer to this nanostructured electrode was compared to that of a planar, mirror polished solid nickel electrode using the limiting current technique, for the reduction of ferricyanide, hexacyanoferrate (III) ion in an undivided cell. The effect of introducing a turbulence promoter into the electrolyte channel was also evaluated for each electrode under steady state conditions. At a Reynolds number of 700, the product of mass transfer coefficient and active electrode area, kLA for the nanostructured nickel electrode increases over 11 times compared to the mirror polished planar nickel electrode. In the presence of a turbulence promoter, the nanostructured nickel electrode shows an approximately 23 times increase in kLA compared to the planar mirror polished nickel electrode. The dimensionless mass transfer correlations Sh=aRebScdLee are compared to others in the literature. © 2012 Elsevier Ltd.

In this study, the mass transport resistance in liquid-phase microextraction (LPME) in a single hollow fiber was investigated. A mathematical model has been developed for the determination of the overall mass transfer coefficient based on the acceptor phase in an unsteady state. The overall mass transfer coefficient in LPME in a single hollow fiber has been estimated from time-dependent concentration of extracted analyte in the acceptor phase while maintaining a constant analyte concentration in the donor phase. It can be achieved either using a high volume of donor to acceptor phase ratio or tuning the extraction conditions to obtain a low-enrichment factor, so that the analyte concentration in the sample is not significantly influenced by the mass transfer. Two extraction systems have been used to test experimentally the developed model: the extraction of Lu(III) from a buffer solution and the extraction of three local anesthetics from a buffer or plasma solution. The mass transfer resistance, defined as a reciprocal values of the mass transfer coefficient, was found to be 1.2 x 103 cm-1 min for Lu(III) under optimal conditions and from 1.96 to 3.3 x 103 cm-1 min for the local anesthetics depending on the acceptor pH and the hydrophobicity of the drug.

The treatment of a synthetic oily wastewater in an airlift submerged membrane bioreactor (AMBR) has been studied. A flat sheet Kubota membrane has been used for this purpose in the reactor with a working volume of 19 L. The volumetric oxygen transfer coefficient, oxygen uptake rate, treatment efficiency and fouling intensity were investigated for various aeration rates (0.2, 0.5, 0.7 and 1 m3/h). Based on the results, a COD removal efficiency of more than 93% - even for the lowest aeration rate – is reported. However, increasing the aeration rate resulted in higher kLa and higher microbial activity. The high aeration intensity resulted in breakage of activated sludge flocs and hence reduction in mean flocs size and release of extracellular polymeric substances (EPS). At an aeration intensity as high as 1m3/h, the maximum irreversible fouling was observed which is due to higher concentration of EPS and colloids that are the major foulants. Although the aeration may scour the membrane surface and avoid the formation of cake layer, it could induce more pore blocking fouling. In the studied range, the 0.7 m3/h is found to be the optimum aeration rate and the alteration of the aeration rate deteriorated the AMBR’s performance.

In this study, the mass transport resistance in liquid-phase microextraction (LPME) in a single hollow fiber was investigated. A mathematical model has been developed for the determination of the overall mass transfer coefficient based on the acceptor phase in an unsteady state. The overall mass transfer coefficient in LPME in a single hollow fiber has been estimated from time-dependent concentration of extracted analyte in the acceptor phase while maintaining a constant analyte concentration in the donor phase. It can be achieved either using a high volume of donor to acceptor phase ratio or tuning the extraction conditions to obtain a low-enrichment factor, so that the analyte concentration in the sample is not significantly influenced by the mass transfer. Two extraction systems have been used to test experimentally the developed model: the extraction of Lu(III) from a buffer solution and the extraction of three local anesthetics from a buffer or plasma solution. The mass transfer resistance, defined as a reciprocal values of the mass transfer coefficient, was found to be 1.2 x 103 cm-1 min for Lu(III) under optimal conditions and from 1.96 to 3.3 x 103 cm-1 min for the local anesthetics depending on the acceptor pH and the hydrophobicity of the drug.

This study of photocatalytic oxidation of phenol over titanium dioxide films presents a method for the evaluation of true reaction kinetics. A flat plate reactor was designed for the specific purpose of investigating the influence of various reaction parameters, specifically photocatalytic film thickness, solution flow rate (1–8 l min−1), phenol concentration (20, 40 and 80 ppm), and irradiation intensity (70.6, 57.9, 37.1and 20.4 W m−2), in order to further understand their impact on the reaction kinetics. Special attention was given to the mass transfer phenomena and the influence of film thickness. The kinetics of phenol degradation were investigated with different irradiation levels and initial pollutant concentration. Photocatalytic degradation experiments were performed to evaluate the influence of mass transfer on the reaction and, in addition, the benzoic acid method was applied for the evaluation of mass transfer coefficient. For this study the reactor was modelled as a batch-recycle reactor. A system of equations that accounts for irradiation, mass transfer and reaction rate was developed to describe the photocatalytic process, to fit the experimental data and to obtain kinetic parameters. The rate of phenol photocatalytic oxidation was described by a Langmuir–Hinshelwood type law that included competitive adsorption and degradation of phenol and its by-products. The by-products were modelled through their additive effect on the solution total organic carbon.

The purpose of this article is to demonstrate how a model can be constructed such that the progress of a submerged fed‐batch fermentation of a filamentous fungus can be predicted with acceptable accuracy. The studied process was enzyme production with Aspergillus oryzae in 550 L pilot plant stirred tank reactors. Different conditions of agitation and aeration were employed as well as two different impeller geometries. The limiting factor for the productivity was oxygen supply to the fermentation broth, and the carbon substrate feed flow rate was controlled by the dissolved oxygen tension. In order to predict the available oxygen transfer in the system, the stoichiometry of the reaction equation including maintenance substrate consumption was first determined. Mainly based on the biomass concentration a viscosity prediction model was constructed, because rising viscosity of the fermentation broth due to hyphal growth of the fungus leads to significant lower mass transfer towards the end of the fermentation process. Each compartment of the model was shown to predict the experimental results well. The overall model can be used to predict key process parameters at varying fermentation conditions.

In this paper, membrane filtration of produced water is studied in terms of its mass transfer coefficient. This filtration process is incorporated to improve the existing OSPAR method in removing dissolved oil. During membrane filtration, concentration nearer to the membrane is higher than the concentration of bulk solution and thus a concentration profile develops. Studying the mass transfer coefficient (MTC) which drives the concentration difference can help us in understanding the phenomena of fouling in membrane. Two models i.e. combined solution diffusion/film theory model (Murthy and Gupta, 1997) and film theory model are compared and the most suitable model to predict the MTC is selected. From the experimental results, it was found that film theory (FT) model is suitable to calculate MTC for produced water samples in our experimental set-up. The models are found to be suitable only at a certain range of differential pressure.