Hossein Bahmanyar

Bio: Hossein Bahmanyar is an academic researcher from University of Tehran. The author has contributed to research in topics: Mass transfer & Mass transfer coefficient. The author has an hindex of 15, co-authored 55 publications receiving 595 citations. Previous affiliations of Hossein Bahmanyar include University of Bradford & Sultan Qaboos University.

The influence of nanoparticles on hydrodynamic characteristics and mass transfer performance in a pulsed liquid–liquid extraction column

Abstract: With respect to the influence of nanoparticles on mass transfer characteristics, limited number of studies available in the literature, deal primarily with gas–liquid systems. In this work, mass transfer performance and hydrodynamic characteristics including static and dynamic dispersed phase hold-ups of nanofluids have been investigated for pulsed liquid–liquid extraction column (PLLEC). The nanofluids used were prepared by dispersing SiO 2 nanoparticles of 0.01, 0.05 and 0.1 volume percent with two different hydrophobicities in kerosene as base fluid using ultrasonication. UV–vis spectrophotometer was also used for evaluation of the nanofluids stability. The results were compared with conditions of no-nanoparticles in the dispersed phase and in the absence of mass transfer effect (no acetic acid as solute). Different pulsation intensities were maintained for the fixed mass flow rates of dispersed ( Q d ) and continuous ( Q c ) phases (with ratio Q c / Q d = 1.2) with mass transfer direction being made from the dispersed phase to the continuous one. The results indicate that in the presence of the nanofluids, static and dynamic dispersed phase hold-ups increased by 23–398%, and 23–257%, respectively, while mass transfer performance was enhanced by 4–60%.

Mass transfer from nanofluid drops in a pulsed liquid-liquid extraction column

Abstract: Mass transfer in gas–liquid systems has been significantly enhanced by recent developments in nanotechnology. However, the influence of nanoparticles in liquid–liquid systems has received much less attention. In the present study, both experimental and theoretical works were performed to investigate the influence of nanoparticles on the mass transfer behaviour of drops inside a pulsed liquid–liquid extraction column (PLLEC). The chemical system of kerosene–acetic acid–water was used, and the drops were organic nanofluids containing hydrophobic SiO2 nanoparticles at concentrations of 0.01, 0.05, and 0.1 vol%. The experimental results indicate that the addition of 0.1 vol% nanoparticles to the base fluid improves the mass transfer performance by up to 60%. The increase in mass transfer with increased nanoparticle content was more apparent for lower pulsation intensities (0.3–1.3 cm/s). At high pulsation intensities, the Sauter mean diameter (d32) decreased to smaller sizes (1.1–2.2 mm), leading to decreased Brownian motion in the nanoparticles. Using an analogy for heat and mass transfer, an approach for determining the mass diffusion coefficient was suggested. A new predictive correlation was proposed to calculate the effective diffusivity and mass transfer coefficient in terms of the nanoparticle volume fraction, Reynolds number, and Schmidt number. Finally, model predictions were directly compared with the experimental results for different nanofluids. The absolute average relative error (%AARE) of the proposed correlation for the mass transfer coefficient and effective diffusivity were 5.3% and 5.4%, respectively.

Studies of drop break‐up in liquid‐liquid systems in a rotating disc contactor. Part I: Conditions of no mass transfer

Abstract: Observations on the break-up of single drops in a rotating disc contactor show that there is a critical rotor speed below which drops of a given size do not break. Weber and Reynolds numbers are required to correlate the data and not simply a Weber number as for turbine agitated systems. The probability of break-up of a drop at the rotor edge is expressed in terms of a Weber number with a lower limit for critical conditions. The mean number of daughter drops produced on break-up is correlated as a simple function of drop diameter based on the critical diameter and agreement is found with data from other types of agitated equipment.

Prediction of enhancement factor for mass transfer coefficient in regular packed liquid–liquid extraction columns

Abstract: Mass transfer coefficients are one of the most important parameters for the design of liquid–liquid extraction columns. The mass transfer coefficients of single drops in a pilot structured packed column have been measured using toluene/acetic acid/water and n-butyl acetate/acetic acid/water systems. Current research shows that theoretical models have failed to predict mass transfer coefficient precisely and are not reliable for design. In this work an empirical correlation for prediction of enhancement factor is developed. Dispersed phase mass transfer coefficients predicted by the proposed correlation are in good compatibility with experimental results. Les cœfficients de transfert de masse figurent parmi les parametres les plus importants a prendre en compte lors de la conception de colonnes d'extraction liquide-liquide. Les cœfficients de transfert de masse de chaque goutte dans une colonne a garnissage structure pilote ont ete mesures grâce a des systemes a base de toluene/d'acide acetique/d'eau et d'acetate de n-butyle/d'acide acetique/et d'eau. La comparaison entre les modeles theoriques et les resultats experimentaux de cœfficients de transfert de masse a montre que ces modeles ne sont pas assez precis pour etre appliques a la conception. Dans cette recherche, les facteurs d'accentuation du cœfficient de diffusion ont ete determines experimentalement et une correlation empirique a ete atteinte pour le facteur d'accentuation. Les cœfficients de transfert de masse de la phase dispersee qui avait ete prevus grâce a la correlation proposee s'harmonisent bien aux resultats des experiences. © 2010 Canadian Society for Chemical Engineering

Small particles, big impacts: A review of the diverse applications of nanofluids

Abstract: Nanofluids—a simple product of the emerging world of nanotechnology—are suspensions of nanoparticles (nominally 1–100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.

A review on the current status of various hydrothermal technologies on biomass feedstock

Abstract: Hydrothermal processing, a thermochemical approach, is an excellent method of converting energy-rich biomass into useful products. This approach offers the advantage of handling biomass with relatively high moisture content by precluding an energy-intensive pretreatment step. Hydrothermal processing is of world-wide interest in view of depleting fossil-fuel reserves and increased environmental greenhouse gas emissions. There is potential to develop this novel technology at demonstration scale. This paper reviews the three hydrothermal technologies, namely hydrothermal liquefaction, gasification and carbonization, to provide insight into the likelihood of commercialization. The study discusses the role of different process parameters that have key impacts on the quality and yield of the desired products. This study also identifies the gaps in the literature including the need to establish a baseline to develop key process models and to perform a techno-economic assessment to get a better sense of the viability of the technology in future.

Hydrogen production from biomass using dark fermentation

Abstract: Hydrogen applicability in the power, chemical and petrochemical industries is constantly growing. Efficient methods of hydrogen generation from renewable sources, including waste products, are currently being developed, even though hydrogen is mainly produced through steam reforming or thermal cracking of natural gas or petroleum fractions. In paper alternative methods of hydrogen production with a particular emphasis on dark fermentation are discussed. The review compiles essential information on strains of bacteria used in the production of hydrogen from waste products in the agroindustry and from lignocellulosic biomass. The effect of such parameters as kind of raw material, method of processing, temperature, pH, substrate concentration, partial pressure of hydrogen, hydraulic retention time, method of inoculum preparation and the type and operating parameters of a reactor on the yield of dark fermentation is discussed. The review aims at presentation of current state of knowledge on the dark fermentation process utilizing waste materials as substrates. The results of investigations with emphasis on the most important issues regarding operating parameters of dark fermentation are also included.

Gasification of biowaste: A critical review and outlooks

Abstract: Gasification is a promising technology for reducing the volume of biowaste feedstock. Further, with the incorporation of steam this thermochemical treatment technology also concomitantly produces H2, a high value energy. This paper aims to summarize the status of biowaste gasification technology and detail the benefits and limitations of different gasification processes, especially for biowaste. First, we compare steam with other gasification agents (oxygen and air) to understand the specific effects of gasification agents on the resulting gas quality and quantity. Second, influencing process factors (reactor configurations, temperature, steam to biomass ratio, and catalyst incorporation) are evaluated in terms of their impact on the resulting H2/CO ratio, gas heating value, gas yield, tar yield, and energy recovery. Third, commercial biowaste gasification applications are detailed and the economics and societal impacts are elucidated. Finally, the current challenges facing the field of gasification and the future outlooks of this technology for reducing biowaste are presented.