Effect Of Different Flow Rates Research Articles

An experimental investigation of heat transfer enhancement of a minichannel heat sink using Al2O3–H2O nanofluid

The thermal performances of a minichannel heat sink are experimentally investigated for cooling of electronics using nanofluid coolant instead of pure water. The Al2O3–H2O nanofluid including the volume fraction ranging from 0.10 to 0.25vol.% was used as a coolant. The effects of different flow rates of the coolant on the overall thermal performances are also investigated. The flow rate was ranged from 0.50 to 1.25L/min as well as the Reynolds number from 395 to 989. The coolant was passed through a custom made copper minichannel heat sink consisting of the channel height of 0.8mm and the channel width of 0.5mm. The experimental results showed the higher improvement of the thermal performances using nanofluid instead of pure distilled water. The heat transfer coefficient was found to be enhanced up to 18% successfully. The nanofluid significantly lowered the heat sink base temperature (about 2.7°C) while it also showed 15.72% less thermal resistance at 0.25vol.% and higher Reynolds number compared to the distilled water.

Experimental investigation of an electrodialysis regenerator for liquid desiccant

Liquid desiccant air-conditioning system (LDAS) is a novel air-conditioner with good energy saving potential. Electrodialysis (ED) regeneration is a novel regeneration method for LDAS, which has a higher performance than the conventional thermal regeneration method. In this paper, an experimental setup was developed to study the performance of ED regenerator for liquid desiccant. Based on experimental results, the current utilization of ED regenerator and the mass transfer rate of desiccant solution on unit area of anion-exchange membrane were experimentally obtained. The effects of different flow rates of regenerated and diluted desiccant solution on the current utilization and the mass transfer rate on unit area of anion-exchange membrane are studied. The results show that the largest mass concentration difference between regenerated desiccant solution at the entrance and the exit of the ED regenerator is 0.011%, and the largest mass concentration difference between regenerated desiccant solution at start and end of the experiment is 0.03%. Meanwhile, the largest current utilization of the experimental system of ED regenerator is 55%. Moreover, the current utilization and the mass flow rate of regenerated desiccant solution will increase with the flow rate of desiccant solution.

Flow dynamics and mass transfer studies in a tubular electrochemical reactor with a mesh electrode

The new strict legislation and regulation to protect the environment, has necessitated the use of clean technology in wastewater treatment. The performance of a tubular electrochemical reactor (TER) with a cylindrical mesh electrode has been investigated for wastewater treatment. The residence time distribution (RTD) and computational fluid dynamics (CFD) were used as tools to study the flow dynamic behavior of the electrolyte within the reactor. The effects of different flow rates on flow dynamics were studied. The results obtained show the positive influence of the mesh electrode on the flow dynamic behavior. The presence of a dead volume and short circuiting in the reactor decreased with an increase in the flow rate. The performance of the TER was experimentally validated by studying the mass transfer and the color removal efficiency and the results show an improvement for higher flow rates.

Artificial neural network (ANN) modeling of dynamic adsorption of crystal violet from aqueous solution using citric-acid-modified rice (Oryza sativa) straw as adsorbent

Rice straw, an abundant, lignocellulosic agricultural residue worldwide, was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The morphological and chemical characteristics of rice straw and acid-modified rice straw were investigated by scanning electron microscopy, surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared spectroscopy. The modification process leads to the increase in the specific surface area and pore size of rice straw. In order to investigate the application potential of the prepared adsorbent to remove a cationic dye (Crystal violet) from its aqueous solution, a continuous adsorption study was carried out in a laboratory scale fixed-bed column packed with acid-modified rice straw. Effect of different flow rates and bed heights on the column breakthrough performance was investigated. Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. In order to determine the most suitable model for describing the adsorption kinetics of Crystal violet in the fixed-bed column system, the Bed Depth Service Time model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN) based model for determining the dye concentration in the column effluent was also developed. An extensive error analysis was carried out between experimental data and data predicted by the models using the following error functions: correlation coefficient (R 2), average relative error (ARE), sum of the absolute error (SAE), and χ2 statistic test. Based on the values of the error functions, the ANN model was most appropriate for describing the dynamic dye adsorption process.

CFD Analysis on the Flow Field of Minimum Quantity Lubrication during External Thread Turning

Minimum quantity lubrication (MQL) is a new cooling technology used in machining process, which is friendly to environment and lower cost. This paper applied computational fluid dynamics (CFD) to analyze flow field of MQL in thread turning. Comprehensively applying droplet breakup method and capillary method, flow field of MQL in cutting zone were analyzed in detail. The results showed that oil mist could enter into cutting zone from sides of chip. And two vortexes existed around cutting zone which could reduce cutting temperature by accelerating heat exchange. Furthermore, flow rate of compressed air had great influence on velocity and diameter of droplets, velocity and pressure distribution of flow field. The effects of different flow rates indicated the larger flow rate was benefit for entering into cutting zone of oil mist.

Artificial neural network (ANN) modeling of adsorption of methylene blue by NaOH-modified rice husk in a fixed-bed column system

In this study, rice husk was modified with NaOH and used as adsorbent for dynamic adsorption of methylene blue (MB) from aqueous solutions. Continuous removal of MB from aqueous solutions was studied in a laboratory scale fixed-bed column packed with NaOH-modified rice husk (NMRH). Effect of different flow rates and bed heights on the column breakthrough performance was investigated. In order to determine the most suitable model for describing the adsorption kinetics of MB in the fixed-bed column system, the bed depth service time (BDST) model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN)-based model was also developed for describing the dynamic dye adsorption process. An extensive error analysis was carried out between experimental data and data predicted by the models by using the following error functions: correlation coefficient (R(2)), average relative error, sum of the absolute error and Chi-square statistic test (χ(2)). Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. All the error functions yielded minimum values for the ANN model than the traditional models (BDST and Thomas), suggesting that the ANN model is the most suitable model to describe the fixed-bed adsorption of MB by NMRH. It is also more rational and reliable to interpret dynamic dye adsorption data through a process of ANN architecture.

Continuous enzymatic interesterification of lard and soybean oil blend: Effects of different flow rates on physical properties and acyl migration

Abstract Continuous enzymatic interesterification is an alternative to chemical interesterification for lipid modification technology which is economically viable for large scale use. A blend of 70% lard and 30% soybean oil was submitted to continuous enzymatic interesterification in a glass tubular bioreactor at flow rate ranging from 0.5 to 4.5 mL/min. The original mixture and the reaction products obtained were examined to determine melting and crystallization behavior by DSC, and analyzed for regiospecific fatty acid distribution. Continuous enzymatic interesterification changed the mixture, forming a new triacylglycerol composition, verified by DSC curves and variation in enthalpy of melting values. The regiospecific distribution of fatty acids was changed by flow variations in the reactor. In the continuous enzymatic interesterification reaction the flow rate of 4.5 mL/min, was more advantageous than slower flow rates, reducing acyl migration and increasing process productivity.

Thomas and artificial neural network models for the fixed-bed adsorption of methylene blue by a beach waste Posidonia oceanica (L.) dead leaves

Posidonia oceanica (L.) is an endemic sea grass in the Mediterranean Sea. Its dead leaves are accumulated in the beaches. Biomass based on dead leaves of P. oceanica is considered as a beach waste. Therefore, they are burned to keep beaches clean. In the present study, an alternative eco-friendly evaluation approach for removal of methylene blue by dead leaves of P. oceanica is studied. Dynamic removal of methylene blue from aqueous solution is performed in a fixed-bed column. Effects of different flow rates and bed heights on column performance are investigated and best flow rate and bed height are observed at 7.28mL/min and 9cm, respectively. Column performance has been modeled with Thomas and Artificial Neural Network models. The results confirm that dead leaves of P. oceanica can be used as a fixed-bed material for the dynamic removal of dyes in the waste waters from textile industry.

Performance of a non-grafted monolithic support for purification of supercoiled plasmid DNA

The use of therapeutics based on plasmid DNA (pDNA) relies on procedures that efficiently produce and purify the supercoiled (sc) plasmid isoform. Several chromatographic methods have been applied for the sc plasmid purification, but with most of them it is not possible to obtain the required purity degree and the majority of the supports used present low capacity to bind the plasmid molecules. However, the chromatographic monolithic supports are an interesting alternative to conventional supports due to their excellent mass transfer properties and their high binding capacity for pDNA. The separation of pDNA isoforms, using short non-grafted monolithic column with CarbonylDiImidazole (CDI) functional groups, is described in the current work. The effect of different flow rates on plasmid isoforms separation was also verified. Several breakthrough experiments were designed to study the effect of different parameters such as pDNA topology and concentration as well as flow rate on the monolithic support binding capacity. One of the most striking results is related to the specific recognition of the sc isoform by this CDI monolith, without flow rate dependence. Additionally, the binding capacity has been found to be significantly higher for sc plasmid, probably because of its compact structure, being also improved when using feedstock with increased plasmid concentrations and decreased linear velocity. In fact, this new monolithic support arises as a powerful instrument on the sc pDNA purification for further clinical applications.

Column performance of uranyl ion exchange on tin(IV) antimonite hydrous oxide

Column chromatographic technique has been utilized to study the column performance of uranyl ion separation on tin(IV) antimonite hydrous oxide matrix. Different flow rates were applied, at 0.6 ionic strength and pH 3, to evaluate the effect of different flow rate on column breakthrough behaviour. Van Demeeter equation was used to emphasize the optimum column conditions. High equivalent to theoretical plate, breakthrough capacity (Q0.5) were also calculated.

Optimization of well placement geothermal reservoirs using artificial intelligence

This research proposes a framework for determining the optimum location of an injection well using an inference method, artificial neural networks and a search algorithm to create a search space and locate the global maxima. A complex carbonate geothermal reservoir (Kizildere Geothermal field, Turkey) production history is used to evaluate the proposed framework. Neural networks are used as a tool to replicate the behavior of commercial simulators, by capturing the response of the field given a limited number of parameters such as temperature, pressure, injection location, and injection flow rate. A study on different network designs indicates that a combination of neural network and an optimization algorithm (explicit search with variable stepping) to capture local maxima can be used to locate a region or a location for optimum well placement. Results also indicate shortcomings and possible pitfalls associated with the approach. With the provided flexibility of the proposed workflow, it is possible to incorporate various parameters including injection flow rate, temperature, and location. For the field of study, optimum injection well location is found to be in the southeastern part of the field. Specific locations resulting from the workflow indicated a consistent search space, having higher values in that particular region. When studied with fixed flow rates (2500 and 4911 m 3/day), a search run through the whole field located two locations which are in the very same region resulting in consistent predictions. Further study carried out by incorporating effect of different flow rates indicates that the algorithm can be run in a particular region of interest and different flow rates may yield different locations. This analysis resulted with a new location in the same region and an optimum injection rate of 4000 m 3/day). It is observed that use of neural network, as a proxy to numerical simulator is viable for narrowing down or locating the area of interest for optimum well placement.

Effect comparison of different flow rate of oxygen inhalation on relieving scapulodynia after laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum

Objective To compare the effect of different flow rate of oxygen inhalation on relieving scapuledynia after laparoscopic cholecystectomy(LC) with carbon dioxide pneumoperitoneum. Methods 100 patients adopted LC were divided into the 2 L/min group (n=50), the 4 Ldmin group (n=50), both re-ceived oxygen inhalation 6 hours after LC. The incidence and degree of scapulodynia and the blood- gas analysis were analyzed. Results The incidence of scapulodynia after LC in the 4 L/min group was signifi-cantly lower than that of 2 L/min group. PaCO2,PaO2 and pH in the 4 L/min group were different from those of the 2 L/min group. Conclusions Increasing flow rate of oxygen inhalation can relieve incidence and degree of scapulodynia after laparoscopic cholecystectomy. Key words: Carbon dioxide pneumoperitoneum; Laparoscopy; Cholecystectomy; Oxygenic in-halation; Scapulodynia

“Stolen” Blood Flow: Effect of an Open Arterial Filter Purge Line in a Simulated Neonatal CPB Model

The purpose of this study was to evaluate the effect of different flow rates and pressures on the degree of shunting of blood flow by the arterial filter purge line in a simulated neonatal cardiopulmonary bypass circuit. The circuit was primed with heparinized bovine blood (hematocrit 24%) and postfilter pressure was varied from 60-180 mm Hg (20 mm Hg increments) using a Hoffman clamp. Trials were conducted at flow rates ranging from 200-600 ml/min (100 ml/min increments). During trials conducted at a postfilter pressure of 60 mm Hg, 42.6% of blood flow was shunted through the purge line at a flow rate of 200 ml/min, whereas only 12.8% of flow was diverted at a flow rate 600 ml/min. During trials conducted at a postfilter pressure of 180 mm Hg, 82.8% of blood flow at 200 ml/min and 25.9% of blood flow at 600 ml/min was diverted through the open arterial purge line. The results of this study confirm that a significant amount of flow is diverted away from the patient when the arterial purge line is open. Shunting of blood flow through the arterial purge line could result in less effective tissue perfusion, particularly at low flow rates and high postfilter pressures. To minimize hypoperfusion injury, a flow probe (distal to the arterial filter) may be used to monitor real-time arterial flow in the setting of an open arterial filter purge line.

High flow nasal oxygen generates positive airway pressure in adult volunteers

The use of non-invasive ventilation (NIV) as an alternative to intubation in respiratory failure is associated with better outcomes in certain conditions. NIV is often poorly tolerated by patients hence precipitating the need for invasive ventilation. High flow nasal (HFN) oxygen delivery is a potential alternative to NIV as it delivers air and oxygen via a humidified circuit at flows greater than those traditionally used with a nasal interface. BODY: Studies of paediatric patient using high flow nasal oxygen therapy have been shown to have similar efficacy as nasal continuous positive airway pressure (CPAP). Although the degree of positive pressure and the effect of different flow rates on positive pressure generation have not been well defined or studied in the adult intensive care population. St. Vincent's Health Human Research and Ethics Committee granted approval to this study and also awarded a $3000 grant. Volunteers were fitted with the Fisher & Paykel high flow nasal interface (RT034) and pharyngeal pressures were recorded with flows from 0 to 60L/min. Expiratory pressures with the mouth closed were higher than those with the mouth open and this was statistically significant (<0.001). Expiratory pressures were higher with the mouth closed and were statistically different (p<0.001). EPPs were higher amongst female subjects compared to male subjects and were statistically different between genders for both open (p<0.05) and closed (p<0.001) measurements. This study has demonstrated that high flow nasal therapy is associated with the generation of significant positive airway pressure in volunteers. In conclusion there is a degree of CPAP generated with the HFN therapy, which is flow dependent and also dependent on whether the person is breathing with mouth open or closed.

Investigation of sol-gel matrices containing crude metallothionein from Scchizosaccharomyces pombe for water treatment applications

The application of silica sol–gel particles containing crude metallothionein (MT) was investigated for cadmium removal from water. The metallothionein was first extracted from the yeast Scchizosaccharomyces pombe, and entrapped in the sol–gel matrices. Then sol–gel particles with the different sizes (ranging from 45 to 225 μm) were made. The effect of different flow rates as well as different particle sizes on adsorption of cadmium was investigated. The particle size has a greater effect on Cd adsorption than flow rate in the system studied. The breakthrough curves in the column were modeled using an empirical two parameter fixed-bed adsorption model. The model relates the changes of cadmium concentration in effluent to the standard deviation (σ) and characteristic of time (t0).

Discrepancies between catheter and Doppler estimates of valve effective orifice area can be predicted from the pressure recovery phenomenon: practical implications with regard to quantification of aortic stenosis severity

ObjectivesWe sought to obtain more coherent evaluations of aortic stenosis severity. BackgroundThe valve effective orifice area (EOA) is routinely used to assess aortic stenosis severity. However, there are often discrepancies between measurements of EOA by Doppler echocardiography (EOADop) and those by a catheter (EOAcath). We hypothesized that these discrepancies might be due to the influence of pressure recovery. MethodsThe relationship between EOAcathand EOADopwas studied as follows: 1) in an in vitro model measuring the effects of different flow rates and aortic diameters on two fixed stenoses and seven bioprostheses; 2) in an animal model of supravalvular aortic stenosis (14 pigs); and 3) based on catheterization data from 37 patients studied by Schöbel et al. ResultsPooling of in vitro, animal, and patient data showed a good correlation (r = 0.97) between EOAcath(range 0.3 to 2.3 cm2) and EOADop(range 0.2 to 1.7 cm2), but EOAcathsystematically overestimated EOADop(24 ± 17% [mean ± SD]). However, when the energy loss coefficient (ELCo) was calculated from EOADopand aortic cross-sectional area (AA) to account for pressure recovery, a similar correlation (r = 0.97) with EOAcathwas observed, but the previously noted overestimation was no longer present. ConclusionsDiscrepancies between EOAcathand EOADopare largely due to the pressure recovery phenomenon and can be reconciled by calculating ELCo from the echocardiogram. Thus, ELCo and EOAcathare equivalent indexes representing the net energy loss due to stenosis and probably are the most appropriate for quantifying aortic stenosis severity.

Surface Plasmon Resonance Spectroscopic Study on Pore-Forming Behavior of Streptolysin O on Supported Phospholipid Bilayers

AbstractA novel supported bilayer membrane was formed on top of a hydrophobic spacer layer of hexyl thioctate (HT) and its application in the detection of pore forming toxins was demonstrated. The formation kinetics, effect of different flow rates on the fusion process of vesicles and perforation by incubation with streptolysin O (SLO) and pristine membranes were investigated. Individual layers of the multilayer structure were successfully characterized with surface plasmon resonance (SPR), and the resulting spectra were analyzed in order to determine the layer thickness and other membrane properties. The interaction of SLO with the pristine biomimetic membrane resulted in a pronounced change in the reflectivity spectrum. Elements of these spectral changes were analyzed to explain the process of toxin binding and pore formation taking place on the lipid membrane.

Carbonisation of bagasse in a fixed bed reactor: influence of process variables on char yield and characteristics

Carbonisation experiments on samples of sugar cane bagasse were conducted in a static fixed bed reactor to determine the effect of process variables such as temperature, heating rate, inert sweep gas flow rate and particle size on the yield and composition of solid product char. Experiments were performed to the final temperatures of 250–700°C with heating rates from 5 to 30°C/min with nitrogen sweep gas flow rate of 350 cc/min. Additional tests were aimed at studying the effect of different flow rates of nitrogen sweep gas from 0 to 700 cc/min during carbonization and different particle size fractions of bagasse. The results showed that as the carbonisation temperature was increased, the yield of char decreased. The reduction in yield was rapid up to a final temperature of 500°C and was slower thereafter. The yield of char was relatively insensitive to the changes in heating rate and particle size. Increasing the sweep gas flow rate to 350 cc/min reduced the yield of char. It appears the presence of inert sweep gas reduced secondary reactions which promoted char formation. The proximate analysis of the char suggests that fixed carbon and ash content increased with temperature. The char obtained at temperatures higher than 500°C have high carbon content and is suitable as renewable fuel and for other applications. The carbonization of bagasse has the potential to produce environmental friendly fuels and can assist in reducing deforestation for the production of charcoal.

Use of Air-Liquid Two-Phase Flow in Hydrophobic Microfluidic Channels for Disposable Flow Cytometers

This paper describes a disposable flow cytometer that uses an air-liquid two-phase microfluidic system to produce a focused high-speed liquid sample stream of particles and cells. The susceptibility of thin liquid columns to instabilities may suggest that focusing of sample liquids with streams of air would be difficult. The design of channel geometry, control of flow rates, and use of appropriate surface chemistries on the channel walls, however, enabled the generation of thin (15–100 μm) and partially bounded sample streams that were stable and suitable for rapid cell analysis. Using an inverted epi-fluorescence microscope with a photo-multiplier tube, we demonstrated that the system is capable of counting the number of beads and C2C12 myoblast cells. The effects of different flow rates and surface chemistries of the channel walls on the air-liquid two-phase flows were characterized using optical and confocal microscopy. Use of air instead of liquids as a sheath fluid eliminates the need for large sheath liquid reservoirs, and reduces the volume and weight requirements. The low manufacturing cost and high volumetric efficiency make the air-sheath flow cytometer attractive for use as a stand-alone device or as an integrated component of bio-artificial hybrid microsystems.

Lipase‐catalyzed alcoholysis with supercritical carbon dioxide extraction 1: Influence of flow rate

AbstractA combined process of lipase (E.C. 3.1.1.3) catalysis and extraction of product with supercritical carbon dioxide was studied. The effect of different flow rates of the extraction fluid on the selective removal of the ethyl esters (EE) synthesized in a lipase‐catalyzed alcoholysis of cod liver oil with ethanol was investigated. The faster the flow rate, the faster the extraction rate and the higher the recovery of EE. For example, after a 270‐min extraction, the total recovery of EE was 1520 mg for a flow rate of 0.3 liter carbon dioxide at atmospheric pressure and room temperature/min (NL/min) as compared to 250 mg when 0.015 NL/min was used. The concentration of EE in the carbon dioxide was found to decrease with increasing flow rate, which indicates that the rate of diffusion of EE limits their extraction at fast flow rates. A high flow rate was found to result in a more selective extraction of EE, i.e., less amounts of other lipid components present in the reaction mixture were coextracted with the EE. Further, by increasing the flow rate, the equilibrium of the reaction was shifted slightly toward ester synthesis. An increase in the flow rate from 0.015 to 0.075 NL/min resulted in an approximately 10% increase in total conversion (from 73 to 82%), whereas only a negligible increase was obtained when the flow rate was increased further to 0.15 NL/min.