Development of a mathematical model of frazil ice evolution based on laboratory tests using a counter-rotating flume

2007 ◽  
Vol 34 (2) ◽  
pp. 210-218 ◽  
Author(s):  
Shuang Ming Wang ◽  
J C Doering
Keyword(s):  
Mathematical Model ◽  
Numerical Models ◽  
Frazil Ice ◽  
Thermal Growth ◽  
Mean Size ◽  
Rotating Flume ◽  
The Mean ◽  
Flow Turbulence ◽  
Turbulence Parameters ◽  
Good Agreement

A mathematical model to simulate the supercooling process and frazil ice evolution in a counter-rotating flume was developed. It considers the effect of frazil ice thermal growth while neglecting several complicated physical processes such as secondary nucleation, flocculation, and (or) break up. The supercooling process, vertical distribution of flow turbulence parameters, and frazil ice number concentration were simulated, as well the variation of the mean size of frazil ice during the supercooling process was modeled. The simulation results from this model show good agreement with experimental data.Key words: frazil ice, turbulence, numerical models, counter-rotating flume, supercooling.

Simulation of the supercooling process and frazil evolution in turbulent flows

2004 ◽  
Vol 31 (6) ◽  
pp. 915-926 ◽  
Author(s):  
Shi Qiang Ye ◽  
Jay Doering
Keyword(s):  
Turbulent Flows ◽  
Heat Balance ◽  
Laboratory Experiments ◽  
Distribution Model ◽  
Secondary Nucleation ◽  
Frazil Ice ◽  
Rotating Flume ◽  
Flow Turbulence ◽  
Log Normal ◽  
Log Normal Distribution

A model to simulate the supercooling process and frazil ice evolution in a counter-rotating flume is developed based on a series of laboratory experiments. The characteristics of the supercooling process were found to be related to air temperature and flow turbulence. Frazil ice growth was observed to follow a log-normal distribution model. The model avoids the need to simulate seeding, secondary nucleation, flocculation–breakup, and gravitational removal. Only the overall heat balance is considered during the entire process. The simulations show good agreements with experimental time–temperature curves and frazil evolution.Key words: supercooling, frazil ice, size distribution, concentration, turbulence, simulation.

Determining Temperature Dependencies of Sand Mould Thermal Properties

2014 ◽  
Vol 790-791 ◽  
pp. 452-457 ◽  
Author(s):  
Paweł K. Krajewski ◽  
Grzegorz Piwowarski ◽  
Witold K. Krajewski
Keyword(s):  
Physical Properties ◽  
Numerical Models ◽  
Mass Density ◽  
Measuring Method ◽  
Casting Method ◽  
Mean Values ◽  
The Mean ◽  
Sand Mould ◽  
Thermo Physical Properties ◽  
Good Agreement

The presented work is aimed at determining thermal diffusivity, thermal conductivity and heat capacity coefficients of silica quartz bentonite foundry sand. The values of the above thermo-physical properties were determined for temperature range of about 30 - 450 °C using theCasting measuring method[1-.The results obtained during the examinations presented in the paper can be useful when formulating boundary conditions in numerical models of heat and mass transfer in the system: casting mould ambient. TheCasting methodallows preserving real conditions during the experiment, i.e. contact of the mass with liquid metal and solidifying casting, and the obtained results are in a good agreement with the mean values available in literature. From the obtained results it follows that examinations should be also focused onthermo-physical properties vs. mass densitydependency.

Optimization of the multichamber crystallizer

1979 ◽  
Vol 44 (4) ◽  
pp. 1239-1245 ◽  
Author(s):  
Jaroslav Nývlt ◽  
Luděk Provazník
Keyword(s):  
Mathematical Model ◽  
Surface Area ◽  
Temperature Difference ◽  
Large Temperature ◽  
Optimization Criteria ◽  
Temperature Distributions ◽  
Crystallization Surface ◽  
Mean Size ◽  
The Mean ◽  
Glauber Salt

Mathematical model of the multichamber crystallizer is proposed and is solved for various combinations of temperature distributions among individual chambers. Results of a series of calculations have demonstrated that the most important factors are the temperatures in the first two chambers of the crystallizer while sufficient crystallization surface area in other chambers suffices for reduction of supersaturation even at a large temperature difference. Optimization of the five-chamber crystallizer with the mean size of product crystals chosen as the optimization criteria is then performed for constants corresponding to crystallization of Glauber salt.

Experimental investigation of the effects of turbulence intensity on frazil ice characteristics

2008 ◽  
Vol 35 (1) ◽  
pp. 67-79 ◽  
Author(s):  
Shawn Clark ◽  
John Doering
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Turbulence Intensity ◽  
Particle Diameter ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Frazil Ice ◽  
Rotating Flume ◽  
The Mean ◽  
Hot Film

The counter-rotating flume at the University of Manitoba was used to conduct a series of 21 laboratory experiments to investigate the effects of turbulence intensity on frazil ice formation and evolution. A detailed study of the velocity and turbulence intensity distributions within the counter-rotating flume was initially conducted using a constant-temperature anemometer equipped with a one-dimensional conical hot-film probe. Five levels of turbulence intensity were generated by five different sets of bed plates and flume wall rotation rates in order to study how turbulence affected the frazil particle size distributions and the statistics related to clear disk-shaped particles. It was found that a lognormal distribution could not be rejected when describing the frazil particle size distributions, regardless of the turbulence intensity of the water. The variation of the mean and standard deviation of particle diameter with turbulence intensity are well described by a parabolic shape. A preliminary equation to describe the variation of the mean and standard deviation of particle diameter as a function of turbulence intensity and time is presented.

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

Batch Crystallization with Crystals Attrition

1993 ◽  
Vol 58 (8) ◽  
pp. 1855-1860 ◽  
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Mathematical Model ◽  
Calcium Sulfate ◽  
Crystal Size ◽  
Theoretical Description ◽  
Secondary Nucleation ◽  
Batch Crystallization ◽  
Batch Time ◽  
The Mean

The dependence of the mean crystal size of the products from batch crystallizers on the batch time occasionally exhibits a maximum, which can be explained by secondary nucleation due to the attrition of crystals. A kinetic equatation of nucleation, comprising a term for crystal attrition, can be used for the theoretical description of such behaviour. A mathematical model of a batch crystallizer with crystal attrition has been verified on the calcium sulfate precipitation.

scholarly journals Effects of topical gel formulation of Ficus carica latex on cutaneous leishmaniasis induced by Leishmania major in BALB/c mice

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ali Pouryousef ◽  
Erfan Eslami ◽  
Sepehr Shahriarirad ◽  
Sina Zoghi ◽  
Mehdi Emami ◽  
...  
Keyword(s):  
Cutaneous Leishmaniasis ◽  
Murine Model ◽  
Leishmania Major ◽  
Considerable Effect ◽  
Ficus Carica ◽  
Control Group ◽  
Topical Gel ◽  
The Third ◽  
Mean Size ◽  
The Mean

Abstract Objectives The current study aimed to evaluate the effects of Ficus carica latex on the treatment of cutaneous leishmaniasis (CL), induced by Leishmania major. A 5% topical gel with F. carica latex was prepared. BALB/c mice were infected by inoculation of amastigotes form of L. major. Thirty BALB/c mice were divided into five groups, where the first group was treated daily, the second group twice per day, and the third group every other day with the 5% topical gel, for 3 weeks. The sizes of the lesions were measured before and during the course of treatment. Results Although the mean size of lesions in the mice group treated with the 5% F. carica gel, especially in the group receiving daily treatment, was less than the mean size of the lesions in the control group, yet, the differences was not statistically significant (p > 0.05). The findings of the current study demonstrated that the 5% F. carica latex with a 3-week course of treatment had no considerable effect in recovery or control of CL induced by L. major in the murine model. Using higher concentration of F. carica latex and with longer treatment lengths may increase its efficacy in the treatment of CL.

scholarly journals Mudrock Microstructure: A Technique for Distinguishing between Deep-Water Fine-Grained Sediments

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 653
Author(s):  
Shereef Bankole ◽  
Dorrik Stow ◽  
Zeinab Smillie ◽  
Jim Buckman ◽  
Helen Lever
Keyword(s):  
Grain Size ◽  
Deep Water ◽  
Sedimentary Facies ◽  
X Ray Diffraction ◽  
Weak Current ◽  
Large Area ◽  
Fine Grained ◽  
Mean Size ◽  
The Mean ◽  
Water Facies

Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is impacted by the natural heterogeneity of the system caused by bioturbation. Based on the microfabric analysis, there is a disparate pattern observed among the sedimentary facies; turbidites are generally bedding parallel due to strong currents resulting in shear flow, contourites are random to semi-random as they are impacted by a weak current, while hemipelagites are random to oblique since they are impacted by bioturbation.

Late endoscopic evaluation of the ostium size after external dacryocystorhinostomy

2020 ◽  
pp. 112067212097604
Author(s):  
Reem R Al Huthail ◽  
Yasser H Al-Faky
Keyword(s):  
Chart Review ◽  
Retrospective Chart Review ◽  
Tertiary Hospital ◽  
Nasal Endoscope ◽  
Long Term Follow Up ◽  
Mean Size ◽  
External Dacryocystorhinostomy ◽  
The Mean

Objective: To evaluate the effect of chronicity on the size of the ostium after external dacryocystorhinostomy (DCR) with intubation. Methods: Design: A retrospective chart review of patients who underwent external DCR with intubation over 10 years from January 2003 at a tertiary hospital. All patients were recruited and examined with rigid nasal endoscope. Results: A total number of 66 (85 eyes) patients were included. The mean age at the time of evaluation was 53.1 years with gender distribution of 54 females (81.8 %). The mean duration ±SD between the date of surgery and the date of evaluation was 33.2 ± 33.6 (6–118 months). Our study showed an overall anatomical and functional success of 98.8% and 95.3%, respectively. The mean size of the ostium (±SD) was 23.0 (±15.7) mm2 (ranging from 1 to 80.4 mm2). The size of the ostium was not a significant factor for failure ( p = 0.907). No statistically significant correlation was found between the long-term duration after surgery and the size of the ostium ( R: 0.025, p = 0.157). Conclusions: Nasal endoscopy after DCR is valuable in evaluating the ostium with no observed potential correlation between the long-term follow-up after surgery and the size of the ostium.

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