Effects Of Volumetric Flow Rate Research Articles

Process optimization and scale-up of toluene nitration in a microchannel reactor using HNO3-AC2O as nitrating agent

Aromatic nitro compounds are an important class of basic chemical raw materials, while traditional nitration methods may cause safety accidents and environmental pollution due to strong exothermicity and presence of sulfuric acid. In this work, aiming to alleviate these issues, the nitration of toluene was conducted in a microchannel reactor with nitric acid and acetic anhydride. The effect of temperature, molar ratio of nitric acid to toluene, mass fraction of acetic anhydride, and residence time on the conversion and selectivity of reaction were systematically investigated, and response surface methodology was used to optimize the process. A mononitrotoluene yield of 99.21 % can be achieved under optimum condition. Meanwhile, in order to better understand the exothermic behavior, toluene nitration by HNO3-AC2O was investigated in the semi-batch calorimeter. Finally, the optimized process was scaled up and effect of volumetric flow rate was investigated. At the selected maximum volumetric flow rate, the overtemperature of the system was 10.9 °C with a 98.3 % yield of mononitrotoluene. Continuous flow mode had a space-time yield nearly two orders of magnitude greater than semi-batch mode. This work can provide guidance for safe, efficient and green synthesis of mononitrotoluene.

Synthesis of Cs3Cu2I5 Nanocrystals in a Continuous Flow System.

Achieving the goal of generating all of the world's energy via renewable sources and significantly reducing the energy usage will require the development of novel, abundant, nontoxic energy conversion materials. Here, a cost-efficient and scalable continuous flow synthesis of Cs3Cu2I5 nanocrystals is developed as a basis for the rapid advancement of novel nanomaterials. Ideal precursor solutions are obtained through a novel batch synthesis, whose product served as a benchmark for the subsequent flow synthesis. Realizing this setup enabled a reproducible fabrication of Cs3Cu2I5 nanocrystals. The effect of volumetric flow rate and temperature on the final product's morphology and optical properties are determined, obtaining 21% quantum yield with the optimal configuration. Consequently, the size and morphology of the nanocrystals can be tuned with far more precision and in a much broader range than previously achievable. The flow setup is readily applicable to other relevant nanomaterials. It should enable a rapid determination of a material's potential and subsequently optimize its desired properties for renewable energy generation or efficient optoelectronics.

Thermal performance improvement of a LS-2 parabolic trough solar collector using porous disks

This study presents a thorough numerical investigation of a LS-2 parabolic trough collector (PTC) to introduce a manufacturable structure with high performance. This is done by considering all influential parameters such as possible design shapes (full, upward half, and downward half), diameters, spacings, and PPI (pores per inch) of porous materials along with thermal and fluidic features of heat transfer fluid used inside the absorber pipe. It is found that the full-disk cases perform better than half-disk options. Moreover, the thermal efficiency of PTC improves by increasing PPI and the diameter of porous disks, as well as by reducing the space gaps between the disks. Studying the effects of volumetric flow rate and inlet flow temperature shows that the thermal efficiency diminishes by increasing inlet temperature and decreasing flow rate. In addition, the variations of Nusselt number and friction factor for all mentioned parameters are studied, and performance evaluation criteria are developed to assess the simultaneous effects of enhancing heat transfer against increasing the pumping power.

Continuous Manufacturing of Microfluidic Fibers Embedded with Ordered Microparticles via Ionic Gelation

Fibers loaded with either particles or cells are widely employed across a variety of fields, including material science, tissue engineering, and pharmaceutical research. However, the concentration of such objects along the fiber length remains stochastic, thus resulting in fibers having heterogeneous properties along their length. We here introduce a new class of material featuring fibers loaded with “equally spaced” microparticles. The fibers were obtained thanks to the combination between the recently discovered viscoelastic particle ordering phenomenon and the well-established process of fiber synthesis via ex situ ionic gelation. We employed a simple experimental apparatus made of a syringe pump connected to a 100 μm tube ending in a calcium chloride bath. The liquid forming the fiber was an aqueous solution of hyaluronic acid and sodium alginate. We studied the effect of volumetric flow rate, sodium alginate concentration, and spinning speed on the fiber diameter and the particle-spacing in the fiber. We also discussed the advantages of this type of fiber over the existing ones and suggested potential applications across several fields.

Laminar Fluid Mixing in Micromixers: Description of Pull‐Push Effects

AbstractA numerical study was performed on laminar mixing of fluids by means of embedded microbarriers against the flow direction in two three‐dimensional T‐micromixers. Two microchannels with different obstacle arrangements were considered, and the effect of volumetric flow rate Q on two‐stream pull‐push motion was investigated. With increasing Q and distance of the barriers to the sidewalls K, different vortices and fluid movement patterns develop in the two micromixers. Maximum mass transfer is obtained for the micromixer with smaller K value. With decreasing K, pull‐push movement strongly affects fluid merging, and the quality of mixing increases. Moreover, the effect of fluid tortuosity was studied, and a direct relationship between hydrodynamic fluid tortuosity and mass transfer was found.

Understanding the effect of counterpressure buildup during syringe injections

The pain felt during injection, typically delivered via a hypodermic needle as a single bolus, is associated with the pressure build-up around the site of injection. It is hypothesized that this counterpressure is a function of the target tissue as well as fluid properties. Given that novel vaccines target different tissues (muscle, adipose, and skin) and can exhibit a wide range of fluid properties, we conducted a study of the effect of volumetric flow rate, needle size, viscosity and rheology of fluid, and hyaluronidase as an adjuvant on counterpressure build-up in porcine skin and muscle tissues. In particular, we found a significant increase in counterpressure for intradermal (ID) injections compared to intramuscular (IM) injections, by an order of magnitude in some cases. We also showed that the addition of adjuvant affected the tissue back pressure only in case of subcutaneous (SC) injections. We observed that the volumetric flow rate plays an important role along with the needle size. This study aims to improve the current understanding and limitations of liquid injectability via hypodermic needles, however, the results also have implications for other technologies, such as intradermal jet injection where a liquid bleb is formed under the skin.

Experimental study of heat transfer by water flowing through smooth and rough rock fractures

It is important to have an accurate understanding of heat transfer process of water flowing through fractures for geothermal energy extraction and utilization. We designed an experiment to study the convective heat transfer characteristics of distilled water pumped through manmade smooth and rough fractures in granite samples. The flow velocity, permeating pressure, confining pressure, inlet and outlet fluid temperature and rock outer-surface temperature were measured and recorded to calculate the heat transfer coefficient. The effects of volumetric flow rate, fracture surface roughness, and outer wall surface temperature on the convective heat transfer process were analyzed. The results indicate that fracture surface roughness has a great influence on the heat transfer characteristics of water flowing through rocks. Overall heat transfer intensity improved along with an increase in rock fracture surface roughness. Our results have implications for geothermal energy extraction and utilization.

Experimental and Numerical Investigation of the Efficiency and Pressure Drop of an Inertial Impactor with Variable Area

The deposition efficiency and pressure drop of inertial impactor with variable area has been studied numerically and experimentally. The effect of volumetric flow rate, vertical barrier, oblique barrier and flexible concave plate versus deposition and impaction efficiency and pressure drop is investigated. Numerical simulation is carried out with DPM (discrete phase method) and turbulent model of SST k-ω. To validate the numerical results a special test rig is designed to study the deposition efficiency of engine oil droplets (blow-by) with a diameter of 0.1 to 6 µm. Experimental Tests are done in 8, 12, 16 and 20 L/min. To ensure the accuracy of the experimental results, all the tests are repeated at least three times for each volumetric flow rate. Gravimetric method is implemented to calculate the deposition efficiency. According to the results, the deposition efficiency is obtained between 73 and 94 percent for different mentioned impactors and different volumetric flow rate. The numerical results are confirmed by experimental results. Using the barriers increase the efficiency maximum 6 percent in different volumetric flow rate. The results show that by reducing the distance between the vertical barrier and the outlet of nozzle, the deposition and impaction efficiency are increased. Also, the Concave flexible plate with vertical barrier located at 1 mm from the outlet of nozzle is the most efficient case.

Fixed-bed adsorption of furfural onto granular activated carbon prepared from sawdust

Furfural is a toxic aromatic aldehyde that can cause a severe environmental problem especially the wastewater drone from petroleum refinery units. In the present work, a useless by-product from local furniture manufacturing industry sawdust was used as raw material for preparation of activated carbon which is chemically activated with phosphoric acid. The effect of adsorption variable which include The effect of volumetric flow rate (13, 38, 68) ml / min, the bed depth (0.03, 0.05, 0.09) m, the particle size (0.297, 0.595, 1.19) mm and initial furfural concentration (50, 150, 250) mg / l on break through curve for fixed bed adsorption column were evaluated. A comparison was made when using commercial activated carbon and prepared activated carbon at the same operation conditions. The results obtained from experimental investigation show that in fixed bed column increasing the volumetric flow rate lead to fast removal of furfural and reducing breakthrough time. Also the breakthrough curve and breakthrough time increase with bed length and decrease volumetric flow rate. And decreasing with increasing furfural concentration and particle size. In the interval of (120) min the value of Ct / Co reach 0.911 and 0.931 for CAC and PAC, respectively. At the best condition, which obtained at volumetric flow rate 38 ml / min, bed depth 0.5 m, particle size 0.595 mm and initial furfural concentration 250 mg / l.

Thermal management of GaN HEMT devices using serpentine minichannel heat sinks

An experimental and numerical investigation of water-cooled serpentine rectangular minichannel heat sinks (MCHS) has been performed to assess their suitability for the thermal management of gallium nitride (GaN) high-electron-mobility transistors (HEMTs) devices. A Finite Element-based conjugate heat transfer model is developed, validated experimentally and used to determine the optimal minichannel width and number of minichannels for a case with a uniform heat flux of 100 W/cm2. The optimisation process uses a 30 point Optimal Latin Hypercubes Design of Experiments, generated from a permutation genetic algorithm, and accurate metamodels built using a Moving Least Square approach. A Pareto front is then constructed to enable the compromises available between designs with a low pressure drop and those with low thermal resistance to be explored and an appropriate minichannel width and number of minichannels to be chosen. These parameters are then used within conjugate heat transfer models of a serpentine MCHS with silicon, silicon carbide, diamond and graphene heat spreaders placed above a GaN HEMT heating source of area 4.8 × 0.8 mm2, generating 1823 W/cm2. A nanocrystalline diamond (NCD) layer with thickness of 2 µm is mounted on the top surface of the GaN HEMT to function as a heat spreader to mitigate the hot spots. The effect of volumetric flow rate and heat spreader thickness on the chip temperature has been investigated numerically and each of these has been shown to be influential. For example, at a volumetric flow rate of 0.10 l/min, the maximum chip temperature can be reduced from 124.7 °C to 96.7 °C by employing a 25 µm thick graphene heat spreader attached to the serpentine MCHS together with a NCD layer compared with a serpentine MCHS without these heat spreaders.

Prediction of induction time for methane hydrate formation in the presence or absence of THF in flow loop system by Natarajan model

The induction time is a time interval to detect the initial hydrate formation, which is counted from the moment when the stirrer is turned on until the first detection of hydrate formation. The main objective of the present work is to predict and measure the induction time of methane hydrate formation in the presence or absence of tetrahydrofuran (THF) as promoter in the flow loop system. A laboratory flow mini-loop apparatus was set up to measure the induction time of methane hydrate formation. The induction time is predicted using developed Kashchiev and Firoozabadi model and modified model of Natarajan for a flow loop system. Furthermore, the effects of volumetric flow rate of the fluid on the induction time were investigated. The results of the models were compared with experimental data. They show that the induction time of hydrate formation in the presence of THF is very short at high pressure and high volumetric flow rate of the fluid. It decreases with increasing pressure and liquid volumetric flow rate. It is also shown that the modified Natarajan model is more accurate than the Kashchiev and Firoozabadi ones in prediction of the induction time.

Abatement of the antibiotic levofloxacin in a solar photoelectro-Fenton flow plant: Modeling the dissolved organic carbon concentration-time relationship

The degradation of solutions of the antibiotic levofloxacin (LVN) in sulfate medium at pH 3.0 has been investigated at pre-pilot scale by solar photoelectro-Fenton (SPEF) process. The flow plant included an FM01-LC filter-press cell equipped with a Ti|Pt anode and a three-dimensional-like air-diffusion cathode, connected to a compound parabolic collector as photoreactor and a continuous stirred tank under recirculation batch mode. The effect of volumetric flow rate on H2O2 electrogeneration from O2 reduction was assessed. Then, the influence of initial LVN concentration and Fe2+ concentration as catalyst on dissolved organic carbon (DOC) removal was thoroughly investigated. LVN was gradually mineralized by SPEF process, with faster DOC abatement at 0.50 mM Fe2+, yielding 100% after 360 min at applied cathodic potential of −0.30 V|SHE. The high mineralization current efficiency (MCE) and low specific energy consumption (ECDOC) revealed the extraordinary role of homogeneous hydroxyl radicals and natural UV light, which allowed the degradation of the antibiotic and its by-products with MCE values greater than 100%. Five cyclic by-products, N,N-diethylformamide and three short-chain linear carboxylic acids were detected by GC-MS and HPLC analyses. A parametric model to simulate the DOC decay versus electrolysis time was implemented for the SPEF pre-pilot flow plant, showing good agreement with experimental data.

Enhancing biogas production of meat industrial wastewater by microwave pretreatment

The effects of microwave pre-treatment of meat industrial wastewater were investigated in this study. The focus of this investigation was to determine the optimum conditions in a continuous flow microwave treating system under which the microwave pre-treatment of meat industrial wastewater would facilitate the maximum biogas yield. Response surface analysis was applied to screen the effects of volumetric flow rate (FR), number of treating (NT) and power of the magnetron (PM).

Biological synthesis of Pt nanoparticles in a microfluidic chip and modeling of the formation process withPBMandCFD

AbstractBACKGROUNDBiological synthesis of platinum nanoparticles (PtNPs) withCacumen platycladi(C. platycladi) in a microfluidic chip and numerical simulation of formation processes were studied. The effect of volumetric flow rate onPtNPs' size distribution was investigated in detail not only by experimental methods but also by means of numerical simulation. Computational fluid dynamics (CFD) and a population balance model (PBM) combined with reactive kinetics were employed to simulatePtNPs' formation and to calculate the particle size distributions (PSD).RESULTSThe experimental results confirmed the validity of the model and its practicality in predicting the formation ofPtNPsandPSDevolution in the microfluidic chip. In addition, the numerical simulation results also tested and verified the accuracy of the results and conclusions acquired from the experiment.CONCLUSIONIt is concluded thatPSDwas influenced not only by mixing efficiency but also by residence time in the microfluidic chip, and that the two factors were determined by volumetric flow rate. There is a specific volumetric flow rate to achieve equilibrium (optimal mixing and residence time) that results in the average particle size reaching its maximum value. This work provides useful insight into the microfluidic biological synthesis ofPtNPsand the influence of volumetric flow rate on size distribution in a microfluidic chip. © 2017 Society of Chemical Industry

PENGARUH DEBIT TERHADAP UNJUK KERJA ALAT PENUKAR KALOR DAN PENURUNAN SUHU RUANGAN

ABSTRACTDue to population growth, industry advance and rapid development, fresh and comfortable air may be difficult to get. Conditioning the air to get comfort environment may be a basic demand for people, but the prices of the device and its operation for this purpose are expensive. This research tries to solve this problem but it is just only to know the capability of the heat exchanger to transfer/ absorb heat and is not to cool the room to be below the ambient temperature. The working fluid used was clean water and the heat exchangers employed were parallel and serpentine which were made of copper pipes with a diameter of 1/4 inch and 1/2 inch (for the header). The volumetric flow rates used were 300 ml/minutes, 400 ml/minutes and 500 ml/minutes. While the heat that should be absorbed by the water from the room is 50 W, 100 W and 150 W. The results show that the effect of volumetric flow rate on heat exchanger performance and room temperature is insignificant. From the pressure drop results, the parallel pipe heat exchanger has lower pressure drops while the serpentine has higher pressure drops.

Microfluidic solvent extraction of La(III) with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (P507) by a microreactor

A new solvent extraction system of extracting La(III) with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (P507) has been investigated to intensify the extraction process in microreactor, and solve the problems like long mixing time, low processing capacity, large factory area occupation, and high energy consumption in the conventional rare earth solvent extraction equipment. In this work, extraction equilibrium studies show that the initial aqueous pH value 4.00 and saponification rate 40% are the optimal operation condition. The effects of volumetric flow rate on extraction efficiency are analyzed, and the results indicate that increasing flow ratio could improve the extraction efficiency greatly, up to almost 100%, and the two phases keep parallel flow while keeping an aqueous-organic interface in the microchannel. The mass transfer rate is proportional to the initial pH and P507 concentration, and approaches almost a constant value at high pH and extractant concentration, and the transfer process between the two phases accompanied with an interface chemical reaction is confirmed to proceed satisfactorily in a short time (residence time=0.37s). The features of the microreactors, i.e., large specific surface area and short diffusion distance are effective for the efficient extraction of La(III).

Continuous-flow biosynthesis of Au–Ag bimetallic nanoparticles in a microreactor

Herein, a microfluidic biosynthesis of Au–Ag bimetallic nanoparticle (NP) in a tubular microreactor, based on simultaneous reduction of HAuCl4 and AgNO3 precursors in the presence of Cacumen Platycladi (C. Platycladi) extract was studied. The flow velocity profile was numerically analyzed with computational fluid dynamics. Au–Ag bimetallic NPs with Ag/Au molar ratios of 1:1 and 2:1 were synthesized, respectively. The alloy formation, morphology, structure, and size were investigated by UV–Vis spectra analysis, transmission electron microscopy (TEM), high resolution TEM, scanning TEM, and energy-dispersive X-ray analysis. In addition, the effects of volumetric flow rate, reaction temperature, and concentration of C. Platycladi extract and NaOH on the properties of the as-synthesized Au–Ag bimetallic NPs were investigated. The results indicated that these factors could not only affect the molar ratios of the two elements in the Au–Ag bimetallic NPs, but also affect particle size which can be adjusted from 3.3 to 5.6 nm. The process was very rapid and green, since a microreactor was employed with no additional synthetic reagents used. This work is anticipated to provide useful parameters for continuous-flow biosynthesis of bimetallic NPs in microreactors.

Numerical Studies on the Performance of Saccardo Ventilation System in Emergency Fire Scenarios

In this study, the influence of volumetric flow rate and inclination angle of air jet is evaluated on the performance of a Saccardo ventilation system in a straight rectangular tunnel in case of fire. Simultaneous effects of volumetric flow rate and inclination angle of jet exiting the Saccardo nozzle on the behavior of smoke plume is considered by studying the structure of velocity profile before the fire source. It is found that this factor has a remarkable influence on the behavior of smoke plume and therefore, on the temperatures experienced near the fire. Besides, the influence of tunnel slope on the performance of the Saccardo system to sweep the plume is investigated. It is shown that the slope effect on the behavior of smoke plume and temperature profiles is completely different for locations before and after the fire, in both negative and positive slopes. Finally a range of volumetric flow rates and inclination angles is proposed as the optimized range of performance in an emergency fire scenario.

The effects of volumetric flow rate and inclination angle on the performance of a solar thermal collector

A solar collector is a device that converts solar energy into heat. This paper presents an experimental study on the influences of volumetric flow rate and inclination angle on the performance of a solar collector. The tests were conducted on a solar energy demonstration system (ET200), which consists of a solar collector, a storage tank, a control and command cabinet and a high power lamp simulating solar energy. For radiation intensity of 1.033kW/m2 and inclination angle of 0°, the results showed that the efficiency of the collector followed a linear relationship versus the flow rate; η=0.68×Qv+49.79 and presented a coefficient of correlation (R2) of 0.9898. Similarly, the increase of the inclination angle from 0° to 60° increased the effectiveness of the collector. A linear relationship; η=0.43×α+53.07 with a high coefficient of determination (R2=0.967) relates the collector efficiency to the inclination angle. It is important to operate at higher mass flow rates and take the collector angle at 0° in order to reach its meaning full efficiency (heating water).

Electrochemical degradation of bisphenol A using a flow reactor with a boron-doped diamond anode

Constant current electrolyses are performed in a filter-press reactor using a boron-doped diamond (Nb/BDD) anode to investigate the effect of volumetric flow rate, temperature, pH, current density, and NaCl addition on the chemical oxygen demand (COD) abatement of a 150mgL−1 bisphenol A (BPA) solution. Only the volumetric flow rate, temperature, and current density significantly affect the COD abatement. However, at 25°C, NaCl addition significantly increases the COD abatement rate at 30mAcm−2, but no effect is observed at 6.5mAcm−2; under optimized hydrodynamic conditions, the best condition in terms of current efficiency and energy consumption occurs at 6.5mAcm−2 and 7.0Lmin−1, in the absence of NaCl, when only 1.7AhL−1 is needed to attain a 90% COD abatement. When comparative electrolyses are carried out at 25°C and 30mAcm−2 using Nb/BDD, Ti–Pt/β-PbO2, and TiO2–RuO2 anodes, the Nb/BDD anode always presents the best performance, in the absence or presence of NaCl. The oxidation performance attained with the Nb/BDD anode using the filter-press reactor is significantly better than those previously reported in the literature for the degradation of BPA using conventional electrochemical cells.