Numerical study of the coupling between reaction and mass transfer for liquid-liquid slug flow in square microchannels

While the benefits of miniaturisation on processes have been widely demonstrated, its impact on microfluidics and local mechanisms such as mass transfer is still little understood. The aim of this work is to simulate coupling between reaction and mass transfer in microchannels for liquid-liquid slug flow. First, the extrapolation to confined flow of the classical model used to calculate interfacial mass fluxes in reactive infinite media was studied. This model consists in estimating transferred fluxes between two phases as a function of the enhancement factor E. Its expression depends on the model used to represent interfacial mass transfer. In infinite media, Lewis and Whitman’s stagnant film theory is generally preferred for its simplicity and its reliability. In the case of confined slug flow, the limitation of such a model to predict interfacial fluxes is highlighted. Secondly, the case of liquid-liquid competitive consecutive reactions in microchannels is considered. This work emphasizes the unfavourable impact of the length between droplets on selectivity. This is a direct consequence of mass transport mechanisms in microchannels

A new photobioreactor for continuous microalgal production in hatcheries based on external-loop airlift and swirling flow

This study deals with the scale of a new photobioreactor for continuous microalgal production in hatcheries. The combination of the state-of-art with the constraints inherent to hatcheries has turned the design into a closed, artificially illuminated and external-loop airlift configuration based on a succession of elementary modules, each one being composed of two transparent vertical interconnected columns. The liquid circulation is ensured pneumatically (air injections) with respect to a swirling motion (tangential inlets). A single module of the whole photobioreactor was built-up to investigate how parameters, such as air sparger type, gas flow rate, tangential inlet, column radius and height can influence radiative transfer, hydrodynamics, mass transfer and biological performances. The volumetric productivities were predicted by modeling radiative transfer and growth of Isochrysis affinis galbana (clone Tahiti). The hydrodynamics of the liquid phase was modeled in terms of global flow behavior (circulation and mixing times, Péclet number) and of swirling motion decay along the column (Particle Image Velocimetry). The aeration performances were determined by overall volumetric mass transfer measurements. Continuous cultures of Isochrysis affinis galbana (clone Tahiti) were run in two geometrical configurations, generating either an axial or a swirling flow. Lastly, the definitive options of design are presented as well as a 120 Liter prototype, currently implemented in a French mollusk hatchery and commercialized

Investigations in an external-loop airlift photobioreactor with annular light chambers and swirling flow

Photosynthetic microorganisms could serve as valuable compounds, but also for environmental applications. Their production under controlled conditions implies to design specific reactors, named photobioreactors, in which light supply is the main constraint. This paper was devoted to an original external-loop airlift photobioreactor (PBR) with annular light chambers in which a swirling motion was induced. The aim was to characterize this novel geometrical configuration in terms of gas–liquid hydrodynamics, and to test its potentiality for algal cultures. This PBR consisted of two identical columns connected by flanges defining tangential inlets, each column being made of two transparent concentric tubes (6 L in liquid volume, 50 m−1 in specific illuminated area). Firstly, the global flow characteristics (circulation and mixing times) were determined by a tracer method and modelled by an axial dispersed plug flow with complete recirculation (Péclet number). By means of a double optical probe, both local and global time-averaged parameters of the gas phase were measured, namely void fraction, bubble velocity, frequency and size. The gas–liquid mass transfer were also characterized, in tap water and in culture medium, by measuring overall volumetric mass transfer coefficients. In a second time, cultures of the microalga Chlamydomonas reinhardtii were run in batch mode. The variations of biomass concentration and pigment content with time from inoculation were successfully obtained. All these findings highlighted: (i) some significant differences in terms of gas–liquid hydrodynamics between the present PBR and the usual airlift systems, (ii) the interest of this configuration for algal cultures, even if complementary studies and technological improvements are still required for definitively validating its scale-up

Studies on the iron-catalyzed Fischer-tropsch process in a laminar flow slurry column reactor

The Fischer-Tropsch process was studied in a laminar flow slurry bubble column reactor. Prior to the experiments, hydrodynamic studies were done in a cold-flow model of the reactor. A mathematical model was also developed for the reactor, based on the kinetic data of an iron-based catalyst. The present modeling approach employed enabled the computation of the extent of gas contraction due to reaction. Six sets of experimental runs were carried out to validate the model, the last utilizing biosyngas, produced by the gasification of willow. The model developed was suitable to predict the performance of the reactor, with the rate parameters adjusted, necessitated by the fact that the catalyst activity changes with time-on-stream. The effect of a number of selected parameters on the Fischer-Tropsch process was also investigated

EVALUASI TINGKAT KEPUASAN PENGGUNA TERHADAP SISTEM INFORMASI WEB TEKNIK.UMPO.AC.ID MENGGUNAKAN METODE EUCS

The existence of an information system can make it easier to provide information and services. The Faculty of Engineering of Muhammadiyah University Ponorogo itself has an information system in the form of a website which is used almost every day by students. teknik.umpo.ac.id is a web address that is owned by the faculty of engineering, sometimes students have a lot of complaints about the information and services provided in it, whether the information is less up to date or even the appearance is a bit confusing when opened via a smartphone. The author aims to evaluate the information system to improve services to students. One method for measuring satisfaction is EUCS or End User Computing Satisfaction. Content variable in Content value gets 42.5% percentage which is included in the category of Disagree, Accuracy (Accuracy) of 62.6% percentage of which is in the category of Agree, Display (Format) with 65.73% of the percentage that is included in the Agree category . Ease of Use (user convenience) with a percentage of 77% included in the Agree category. On time (Timeliness) with a percentage rate of 29% which is included in the category of Disagree. The dominant factor in creating user satisfaction in the EUCS method on the technical website.umpo.ac.id is the variable that has the highest mean (mean), namely the ease of use variable which reaches a value of 77%, while the variable which has the lowest mean (mean), which is the Timeliness variable with a percentage of 29%

Global and local hydrodynamics of bubble columns: effect of gas distributor

Global (level swell) and local (WMS – Wire Mesh Sensor) measurements were made on waters of different purities and air, in a cylindrical laboratory bubble column (2 m tall, 0.127 m dia) using two different gas distributors: a perforated plate (to produce homogeneous flow) and a spider sparger (to produce heterogeneous flow). The level swell method provided the steady space-averaged gas holdup/gas flow rate data. The WMS method provided the actual gas holdups and bubble sizes resolved in time and space at one cross-sectional horizontal plane (1 m above distributor), whose integration yields the timeaveraged data. The following results were obtained: The global and local data agree relatively well; there are distinct differences between the radial profiles and bubble size distributions between the two main flow regimes; the local information identifies why the predictions of published models, which account for the smaller and larger bubbles in the flow, may not perform well; the modelling approaches based on the hindrance and enhancement concepts prove to be suitable for the flow regime identification and description, including the transition range between the homogeneous and heterogeneous flows; based on the hydrodynamics, the specific interfacial area is obtained, together with the mass transfer coefficient