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M Luque D De Castro - One of the best experts on this subject based on the ideXlab platform.

  • fast quality monitoring of oil from prefried and fried foods by focused microwave assisted soxhlet extraction
    Food Chemistry, 2002
    Co-Authors: J L Luquegarcia, Maria Carmen Dobarganes, Joaquin Velasco, M Luque D De Castro
    Abstract:

    Abstract A new method for fast quality monitoring of fat from prefried and fried meat and fish is proposed. Prefried and fried samples were extracted with a focused microwave-assisted Soxhlet extractor. The main factors contributing to the extraction efficiency, namely microwave irradiation Power, Number of cycles and microwave irradiation time were optimized by means of a central composite design based on two level-three factors factorial design. This method has allowed us to carry out the extraction of lipids from prefried and fried samples with qualitative and quantitative results similar to those provided by the usual methods (both manual and conventional Soxhlet extraction). A drastic reduction of the procedure time (55 min versus 8 h) is achieved with similar reproducibility to that provided by the conventional method. In addition, the proposed method is cleaner than conventional Soxhlet as 75–80% of the extractant is recycled.

  • determination of the oil content of seeds by focused microwave assisted soxhlet extraction
    Chromatographia, 2000
    Co-Authors: L E Garciaayuso, Joaquin Velasco, Maria Carmen Dobarganes, M Luque D De Castro
    Abstract:

    Soybean, rape and sunflower lipids have been extracted with a focused microwave-assisted Saxhlet extractor. The main factors affecting extraction efficiency, namely microwave irradiation Power, Number of cycles and microwave irradiation time were optimised by means of a Power, Number of cycles and microwave irradiation time were optimised by means of a central composite design based on a two-level-three-factor factorial design. A study of the influence of particle size on the extraction procedure was also performed. The results obtained were compared with those obtained by use of an ISO method using a conventional Soxhlet extractor. Quantitative results for lipid content based on gravimetric determinations and qualitative results based on analysis of fatty acid methyl esters and polymeric compounds were similar to those obtained by Soxhlet extraction with hexane. Substantial reduction of sample manipulation. analysis time and solvent wastage is achieved by use of the proposed method.

J B Joshi - One of the best experts on this subject based on the ideXlab platform.

  • dispersed phase hold up effective interfacial area and sauter mean drop diameter in annular centrifugal extractors
    Chemical Engineering Research & Design, 2009
    Co-Authors: B D Kadam, S B Koganti, J B Joshi, R. N. Patil
    Abstract:

    Abstract Annular centrifugal extractors (ACE), based on the principle of Taylor–Couette flow, offer potential advantages over the existing conventional extraction equipments in many of the engineering applications. In the present work, dispersed phase hold-up (∈D) and effective interfacial area ( a ) have been measured in 30, 75 and 250 mm rotor diameter annular centrifugal extractors over a wide range of Power consumption (0.4  a , and d3,2, which are expected to be useful for practicing engineers. Power consumption was also measured for 40, 60 and 100 mm diameter rotors and an appropriate and simple correlation for Power Number for ACE has been proposed.

  • hollow self inducing impellers flow visualization and cfd simulation
    Chemical Engineering Science, 2007
    Co-Authors: B N Murthy, N A Deshmukh, Ashwin W Patwardhan, J B Joshi
    Abstract:

    Abstract The experimental fluid dynamics (EFD) as well as computational fluid dynamics (CFD) studies were performed for hollow self-inducing agitator system. The system is described in detail elsewhere [Deshmukh, N.A., Patil, S.S., Joshi, J.B., 2006. Gas induction characteristics of hollow self-inducing impeller. Transactions of the Institution of Chemical Engineers 84(A2), 124–132]. The low pressure regions on the impeller blade were determined by single phase CFD simulations. These results were validated with the experimentally measured Power Number ( N P ) . Then with the help of single phase CFD results, the orifices were drilled on the impeller blade in low pressure regions. Gas induction rate ( Q G ) , Power consumption ( P ) and overall fractional gas hold-up ( ϵ G ) were measured experimentally. The comparison of gas induction rates for both the hole locations has been presented. The two phase CFD simulations yielded satisfactory predictions and proved to be most promising for the design of efficient gas-inducing system.

  • effect of impeller design on the flow pattern and mixing in stirred tanks
    Chemical Engineering Journal, 2006
    Co-Authors: T Kumaresan, J B Joshi
    Abstract:

    The flow pattern and Power Number in a vessel depend on the impeller blade angle, Number of blades, blade width, blade twist, blade thickness, pumping direction and interaction of flow with the vessel wall. Measurements of the Power consumption and flow pattern have been carried out in a stirred vessel of 0.5 m diameter for the range of impellers to study the effect of blade shape on the flow pattern. The comparison of the flow pattern (average velocity, turbulent kinetic energy, maximum energy dissipation rate, average shear rate and turbulent normal stress) has been presented on the basis of equal Power consumption to characterize the flow generated by different impeller geometries. Comparisons of LDA measurements and CFD predictions have been presented. The good comparison indicates the validity of the CFD model.

Suzanne M Kresta - One of the best experts on this subject based on the ideXlab platform.

  • impeller characterization and selection balancing efficient hydrodynamics with process mixing requirements
    Aiche Journal, 2012
    Co-Authors: Marcio B Machado, Jose Roberto Nunhez, David S Nobes, Suzanne M Kresta
    Abstract:

    Current literature relies almost exclusively on the Power Number to compare and characterize impellers. Industrial mixing requirements may rely on conditions far away from the impeller. A protocol is proposed to compare impellers designed for turbulent mixing on the basis of impeller hydrodynamic performance and mixing process objectives. A hydrofoil impeller (KPC), and a mixed-flow impeller (45° down-pumping PBT), each at two diameters, were used to test the protocol. Fourteen measures were considered. Five are recommended for full characterization: Power Number, momentum Number, and peak rate of dissipation of turbulent kinetic energy to characterize conditions at the impeller; Power at just-suspended speed to compare the efficiency of solids suspension at the bottom of the tank; and point of air entrainment as a measure of turbulence penetration to the free surface. These five measures provide complete information about mixing performance and good differentiation between the impellers and geometries. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2573–2588, 2012

  • air entrainment in baffled stirred tanks
    Chemical Engineering Research & Design, 2007
    Co-Authors: S. Bhattacharya, D. Hébert, Suzanne M Kresta
    Abstract:

    Abstract The impeller speed at which air is first entrained from the surface of a stirred tank ( N E ) is an operational limit. Where air entrainment is desirable, it is a lower limit, but where air entrainment is detrimental it is an upper limit. This study (1) determines parameters which affect N E and (2) develops a mechanistic model of air entrainment. Experiments were conducted to determine the effect of impeller submergence, impeller diameter, baffle geometry, and the physical properties of the fluid on N E for an up-pumping (PBTU), and a down-pumping pitched blade turbine (PBTD). Mean and RMS velocity profiles were measured for selected cases using laser Doppler velocimetry (LDV). Using this data, air entrainment in stirred tanks and at other free surfaces is compared and is found to depend on the balance between gravity, surface tension and surface turbulence. There must be sufficient turbulence at the surface to overcome surface tension and form bubbles. The entrained bubble size is determined by the mean flow below the surface, which acts to pull the bubbles into the tank. It is shown that impeller variables, such as the Power Number, impeller speed and diameter, cannot predict the point of air entrainment at the surface. The key predicting variable is the ratio of u , the RMS velocity at the surface, to the mean downward velocity U . At the point of air entrainment, this velocity ratio just balances the physical properties of the fluid.

  • the effect of impeller and tank geometry on Power Number for a pitched blade turbine
    Chemical Engineering Research & Design, 2002
    Co-Authors: D Chapple, Suzanne M Kresta, A Wall, Arti Afaca
    Abstract:

    Previous studies of the Rushton turbine have shown that the Power Number is sensitive to the details of impeller geometry, and in particular to the blade thickness, but is independent of the impeller diameter to tank diameter ratio. In this paper, a similar study is reported for the pitched blade impeller. The results show that the Power Number is independent of blade thickness, but dependent on the impeller to tank diameter ratio. This is exactly the opposite result to that observed for the Rushton turbine. Physical explanations are given for the differences in behaviour between the two impellers. For the Rushton turbine, Power consumption is dominated by form drag, so details of the blade geometry and flow separation have a significant impact (30%) on the Power Number. For the pitched blade impeller, form drag is not as important, but the flow at the impeller interacts strongly with the proximity of the tank walls, so changes in the position of the impeller in the tank can have a significant impact on the Power Number.

Basudeb Munshi - One of the best experts on this subject based on the ideXlab platform.

  • numerical investigation of hydrodynamic behavior of shear thinning fluids in stirred tank
    Journal of The Taiwan Institute of Chemical Engineers, 2015
    Co-Authors: Akhilesh Khapre, Basudeb Munshi
    Abstract:

    Abstract A simulation study reported on the velocity fields and the entropy generation of non-Newtonian fluids in a baffled stirred tank with Rushton turbine impeller. Two shear thinning fluids, carboxymethylcellulose (CMC) and xanthan gum (XG), with flow index ( n ) varying in the range from 0.64 to 0.85 are used as the working fluid. The steady state multiple reference frame and the realizable k – e turbulence model is used for numerical simulation. The predicted velocities for a CMC solution with n  = 0.85 compared with literature data, and overall good agreement observed. The effect of flow index on Reynolds Number similarity, Power Number and flow Number also studied. The present work also determines the entropy generation due to the fluid flow. The CFD simulation is applied to predict the effect of size of the impeller blade, impeller clearance, fluid flow behavior index and rotations of impeller on the spatial distribution of the total entropy generation.

  • numerical comparison of rushton turbine and cd 6 impeller in non newtonian fluid stirred tank
    World Academy of Science Engineering and Technology International Journal of Chemical Molecular Nuclear Materials and Metallurgical Engineering, 2014
    Co-Authors: Akhilesh Khapre, Basudeb Munshi
    Abstract:

    A computational fluid dynamics simulation is done for non-Newtonian fluid in a baffled stirred tank. The CMC solution is taken as non-Newtonian shear thinning fluid for simulation. The Reynolds Average Navier Stocks equation with steady state multi reference frame approach is used to simulate flow in the stirred tank. The turbulent flow field is modelled using realizable k-e turbulence model. The simulated velocity profiles of Rushton turbine is validated with literature data. Then, the simulated flow field of CD-6 impeller is compared with the Rushton turbine. The flow field generated by CD-6 impeller is less in magnitude than the Rushton turbine. The impeller global parameter, Power Number and flow Number, and entropy generation due to viscous dissipation rate is also reported. Keywords—Computational fluid dynamics, non-Newtonian, Rushton turbine, CD-6 impeller, Power Number, flow Number, viscous dissipation rate.

Andrzej W Pacek - One of the best experts on this subject based on the ideXlab platform.

  • the effect of stator geometry on the flow pattern and energy dissipation rate in a rotor stator mixer
    Chemical Engineering Research & Design, 2009
    Co-Authors: Adi T Utomo, M Baker, Andrzej W Pacek
    Abstract:

    Abstract The effect of stator geometry on the flow pattern and energy dissipation rate in a batch rotor–stator mixer has been investigated using sliding mesh method with standard k–ɛ turbulence model. It has been found that for the stators with narrow openings (small width-to-depth ratio) the liquid at certain distance from stator rotated in the opposite direction to the rotor rotation. This opposite rotation was induced by the strong circulation flows behind the jets. The predicted Power Numbers for the stators with circular and square openings were about 10% lower than experimental data and the Power Number for stator with slot openings was about 20% lower. The simulation results showed that the Power Number was proportional to the total flowrate. For all stators, about 50–60% of energy supplied by the rotor dissipated in the rotor swept region and approximately 25% in the jet region. The fraction of energy dissipated in the hole region was 12–15% for stators with narrow opening and only 8% for stator with wide opening. The order of magnitude of energy dissipation rate in each region (rotor swept region, holes and jets) was practically the same for all stators; however, the distribution of energy dissipation rate in the hole was more uniform in stator with narrow openings.

  • the influence of impeller type on mean drop size and drop size distribution in an agitated vessel
    Chemical Engineering Science, 1999
    Co-Authors: Andrzej W Pacek, Saethawat Chamsart, A W Nienow, A Bakker
    Abstract:

    Abstract In most work on agitated liquid–liquid dispersions, Rushton turbines have been used. Here, mean drop size and drop size distributions are reported for six different impellers covering 3 generic types over a range of mean specific energy dissipation rates. Both viscous and non-viscous dispersed phases have been used at concentrations by volume of 1 and 5%. It has been found that at the same mean specific energy dissipation rate, low Power Number impellers (whether of the so-called “ultra-high shear” or “high flow” type) all produced similar sized drops at equilibrium which were much smaller than those found with two “high shear”, high Power Number impellers, i.e., the standard Rushton turbine and another six-blade disc impeller. By considering the energy dissipation rate to be confined to the impeller swept volume, these equilibrium drop size could be approximately correlated. The low Power Number impellers also achieved that equilibrium more rapidly and the drop size distributions in the dispersions produced by them were narrower than those formed when agitated by the Rushton turbine and the other six-blade disc impeller. However, further analysis of the flow in the impeller region and the inclusion of advanced coalescence models would appear to be required in order to enhance the interpretation of these results.