Approximate relations for determining the activity coefficient at very low concentration by the method of variation of solute concentration

1985 ◽  
Vol 50 (3) ◽  
pp. 704-711 ◽  
Author(s):  
Bohuslav Doležal ◽  
Robert Holub
Keyword(s):  
Contact Time ◽  
Vapour Phase ◽  
Solute Concentration ◽  
Experimental Procedure ◽  
Low Concentration ◽  
Gas Phases ◽  
Simplifying Assumptions ◽  
Computer Calculations ◽  
Manual Calculation ◽  
Good Agreement

The calculation of activity coefficients at very low concentration is described from the experimental data obtained by the method of the variation of solute concentration for a way of saturation with ensured sufficiently long contact time of the liquid and gas phases and intensive stirring of both phases when the amount of the observed component in the vapour phase above the solution is negligible with regard to its content in the liquid phase. Two variants of experimental procedure were considered: stripping by a pure inert gas and by a gas saturated with solvent vapours. The relations derived can be used either directly for computer calculations or on introducing some simplifying assumptions for a rapid manual calculation with a good agreement of the results.

Interaction Between Impeller and Volute of Pumps at Off-Design Conditions

1986 ◽  
Vol 108 (1) ◽  
pp. 12-18 ◽  
Author(s):  
J. A. Lorett ◽  
S. Gopalakrishnan
Keyword(s):  
Analytical Solution ◽  
Flow Behavior ◽  
Cyclic Variation ◽  
Test Results ◽  
Flow Parameters ◽  
Pump Output ◽  
Simplifying Assumptions ◽  
Radial Thrust ◽  
Relative Flow ◽  
Good Agreement

In a centrifugal pump of volute type, the respective characteristics of the impeller and the volute are such that at only one operating point can the flow parameters be constant along the length of the volute. At off-design conditions the mismatching of characteristics causes variations of velocity and pressure along the periphery of the impeller. This in turn forces cyclic variation of the flow in the impeller channels, introduces variations of the inlet incidence and contributes significantly to the direction and the magnitude of the radial thrust. Furthermore, below a certain pump output, a complete flow reversal occurs over a part of the impeller periphery, thus explaining the onset of recirculation. The paper describes the calculation approach used to derive this aspect of the flow behavior. Because of difficulties in obtaining a closed analytical solution, a step by step computation is employed. Beginning with arbitrarily chosen conditions at the volute tongue, the program computes the flow parameters for following segments, using the continuity and the momentum equations, until the exit from the last segment is reached. The inherent unsteadiness of the relative flow in the impeller is explicitly accounted for. Since the inflow and the velocity in the first segment depend upon the exit conditions of the last, the initial input must be modified, and the computation repeated, until the values are compatible with the exit conditions. In spite of several simplifying assumptions, the results of the calculations show very good agreement with published test results.

An evaluation of fire-plume properties simulated with the Fire Dynamics Simulator (FDS) and the Clark coupled wildfire model

2006 ◽  
Vol 36 (11) ◽  
pp. 2894-2908 ◽  
Author(s):  
Ruiyu Sun ◽  
Mary Ann Jenkins ◽  
Steven K Krueger ◽  
William Mell ◽  
Joseph J Charney
Keyword(s):  
Fluid Dynamics ◽  
Data Sets ◽  
Fire Plume ◽  
Fire Dynamics ◽  
Fire Model ◽  
Fire Dynamics Simulator ◽  
Physically Based ◽  
Vertical Grid ◽  
Simplifying Assumptions ◽  
Good Agreement

Before using a fluid dynamics physically based wildfire model to study wildfire, validation is necessary and model results need to be systematically and objectively analyzed and compared to real fires, which requires suitable data sets. Observational data from the Meteotron experiment are used to evaluate the fire-plume properties simulated by two fluid dynamics numerical wildfire models, the Fire Dynamics Simulator (FDS) and the Clark coupled atmosphere–fire model. Comparisons based on classical plume theory between numerical model and experimental Meteotron results show that plume theory, because of its simplifying assumptions, is a fair but restricted rendition of important plume-averaged properties. The study indicates that the FDS, an explicit and computationally demanding model, produces good agreement with the Meteotron results even at a relatively coarse horizontal grid size of 4 m for the FDS, while the coupled atmosphere–fire model, a less explicit and less computationally demanding model, can produce good agreement, but that the agreement is sensitive to surface vertical-grid sizes and the method by which the energy released from the fire is put into the atmosphere.

Effects of Various Parameters on Nanofluid Thermal Conductivity

2006 ◽  
Vol 129 (5) ◽  
pp. 617-623 ◽  
Author(s):  
Seok Pil Jang ◽  
Stephen U. S. Choi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Volume Fraction ◽  
Heat Transfer Fluids ◽  
New Concepts ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Thermal Phenomena ◽  
First Time ◽  
Good Agreement

The addition of a small amount of nanoparticles in heat transfer fluids results in the new thermal phenomena of nanofluids (nanoparticle-fluid suspensions) reported in many investigations. However, traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain the thermal behavior of nanofluids. Recently, Jang and Choi proposed and modeled for the first time the Brownian-motion-induced nanoconvection as a key nanoscale mechanism governing the thermal behavior of nanofluids, but did not clearly explain this and other new concepts used in the model. This paper explains in detail the new concepts and simplifying assumptions and reports the effects of various parameters such as the ratio of the thermal conductivity of nanoparticles to that of a base fluid, volume fraction, nanoparticle size, and temperature on the effective thermal conductivity of nanofluids. Comparison of model predictions with published experimental data shows good agreement for nanofluids containing oxide, metallic, and carbon nanotubes.

Absorption of Methyl Orange by Modified Fly Zeolites

2012 ◽  
Vol 476-478 ◽  
pp. 1365-1369 ◽  
Author(s):  
Xiao Hua Yu ◽  
Hai Liang Lü ◽  
Guo Wei Zhou ◽  
Li Guo Zhou ◽  
Yong Chun Zhang
Keyword(s):  
Methyl Orange ◽  
Contact Time ◽  
Adsorption Mechanism ◽  
Cetyl Trimethyl Ammonium Bromide ◽  
Orthogonal Experiment ◽  
Solution Temperature ◽  
Ammonium Bromide ◽  
Solution Ph ◽  
Cetyl Trimethyl Ammonium ◽  
Good Agreement

In the present study, three kinds of zeolite (NaP1, NaA, and NaX) were synthesized by a hydrothermal method. These zeolites were modified by cetyl trimethyl-ammonium bromide (CTAB), and used to adsorb methyl orange (MO). NaP1 had the highest adsorption capacity, with a 99.7% MO removal percentage. An orthogonal experiment was conducted to determine the influence of adsorbent dosage, solution pH, initial MO concentration, contact time, and solution temperature on NaP1. The results showed that the initial MO concentration had the most significant effect. The adsorption isotherms of the zeolites are in a good agreement with the Langmuir formula, and the adsorption mechanism is also discussed.

Nanofluid Extinction Coefficients for Photothermal Energy Conversion

2011 ◽  
Author(s):  
Robert A. Taylor ◽  
Patrick E. Phelan ◽  
Ronald Adrian ◽  
Ravi Prasher ◽  
Todd P. Otanicar
Keyword(s):  
Bulk Properties ◽  
Extinction Coefficients ◽  
Energy Harvesters ◽  
Nanoparticle Suspensions ◽  
Model Predictions ◽  
Testing Data ◽  
Simplifying Assumptions ◽  
Solar Thermal Collectors ◽  
Base Liquid ◽  
Good Agreement

Suspensions of nanoparticles in liquids (i.e. nanofluids) have been shown to dramatically affect thermal and optical properties of the base liquid at low particle loadings [1–3]. Recent studies by the co-authors have indicated that selected nanofluids are promising as solar energy harvesters [4,5]. In order to determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, the extinction coefficient of real nanofluids must be established. Although it is relatively straight-forward to model these properties from knowledge of bulk properties, with the help of some simplifying assumptions, real spectroscopy tests do not always match these calculations. This study compares model predictions of extinction coefficients to spectroscopic measurements. Unfortunately, the models and the optical testing data do not show very good agreement. Some possible reasons for this are discussed. Also, some simple experiments are presented to investigate the extent of scattering in nanoparticle suspensions. As alluded to above, all of these tests are conducted on nanofluid compositions which are considered to be suitable for solar thermal collectors.

scholarly journals Antifungal properties of sodium peroxide and sodium hypochlorite as a denture cleanser for full acrylic denture in vitro

2008 ◽  
Vol 20 (1) ◽  
Author(s):  
Gantini Subrata
Keyword(s):  
Sodium Hypochlorite ◽  
Contact Time ◽  
Optimum Concentration ◽  
Sodium Peroxide ◽  
Antifungal Effect ◽  
Low Concentration ◽  
Base Solution ◽  
Denture Cleansers ◽  
Antifungal Efficacy

Widely used materials are reported as denture cleansers are peroxide and hypochlorite. Many contradictions on the effectiveness of the commercial peroxide base solution against Candida albicans (C. albicans). Low concentration sodium hypochlorite (0.5%) is used as a household sanitizer. But it is still unknown whether it has an antifungal effect, what is the optimum concentration and contact time to destroy the yeast. The purpose of this study is to examine the antifungal efficacy of commercial peroxide-based soaking solution and low concentration sodium hypochlorite against C. albicans, to determine the optimum concentration and contact time, and at the end, to obtain an effective denture soaking solution which is safe to use, easy to get, affordable and could be used to destroy C. albicans on dentures. The research conducted was an in vitro practical test for surface disinfectant. Sixty plates of acrylic which were already incubated with C. albicans are immersed in peroxide and hypochlorite base soaking solution in different concentration and contact time. The result showed that peroxide base was not effective to C. albicans and hypochlorite base solution can destroy C. albicans in 10 minutes at a concentration of 0,125%. Thus, the use of low concentration sodium hypochlorite as a denture soaking solution can be suggested.

Vapour growth, morphology, absolute structure and pyroelectric coefficient of meta-nitroaniline single crystals

2019 ◽  
Vol 52 (3) ◽  
pp. 564-570 ◽  
Author(s):  
Rolf Hesterberg ◽  
Michel Bonin ◽  
Martin Sommer ◽  
Matthias Burgener ◽  
Bernhard Trusch ◽  
...  
Keyword(s):  
Room Temperature ◽  
Vapour Phase ◽  
Pyroelectric Coefficient ◽  
Growth Speed ◽  
Published Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Absolute Structure ◽  
Good Agreement

The growth speed of (hkl) faces in the vapour phase, the absolute structure obtained by X-ray crystallography, and the value and the sign of the pyroelectric coefficient of meta-nitroaniline (mNA) were analysed in detail. The in situ observation of morphologically well developed faces of several mNA crystals growing in evacuated ampoules reveals no pronounced growth speed anisotropy for polar faces defining the unique axis 2 of the mm2 group. Scanning pyroelectric microscopy confirms mono-domain mNA crystals. X-ray measurements in the space group Pca21 show that the molecular planes coincide with the {\bar 211} and {\bar 2\bar 1\bar 1} faces, and the nitro groups cover the {201} face in the opposite direction to the crystal tip, characterizing the polar habitus studied here. At room temperature, the sign of the pyroelectric coefficient is positive for a measured effective value of 6.3 µC m−2 K−1, in good agreement with values reported by other authors. From previous elastic and piezoelectric published data, the secondary pyroelectric effect was calculated to be positive and far greater than the effective one, yielding a negative value for the primary pyroelectric coefficient.

An adaptive delay discounting procedure for the E-Prime programming environment

2017 ◽  
Author(s):  
Ray Norbury
Keyword(s):  
Delay Discounting ◽  
Area Under The Curve ◽  
Temporal Discounting ◽  
Hyperbolic Discounting ◽  
Programming Environment ◽  
Software Suite ◽  
Experimental Procedure ◽  
Individual Level ◽  
The Individual ◽  
Good Agreement

Background and objective: Delayed rewards are commonly perceived as less valuable than immediate rewards, a phenomenon referred to as either delay discounting or temporal discounting. Here, an adaptive discounting procedure developed for the E-Prime programming environment and an associated analysis script implemented in Excel are described. Methods: The experimental procedure was developed in E-Prime 2.0.10.242 and an associated analysis workbook in Excel 2013. Area under the curve (AUC) and hyperbolic discounting were used to measure delay discounting.Results: Example data from a sample (n= 19, mean age 21, 14 females) are presented. There was good agreement between AUC and log k values (hyperbolic) (AUC 100 and logK 100 was r(19) = -.889, p < .001, AUC 1000 and logK 1000, r(19) = -.906, p < .001 and AUC 10000 and logK 10000, r(19) = -.872, p < .001. At the individual level, the fit of the hyperbolic discounting function to the data was generally good (R2 values ranged between .88 and .97)Conclusions: An adaptive delay discounting procedure within the E-Prime programming environment and an associated analysis script (executed in Excel) are described. This implementation, freely available to the scientific community, may be suited to laboratories with limited programming resources or experience that intend to use this software suite for developing and implementing experimental paradigms.

Modeling of Ram Extrusion Process and Optimal Die Design

1996 ◽  
Author(s):  
Qingwen Deng ◽  
Yuyi Lin
Keyword(s):  
Analytical Model ◽  
Model Development ◽  
Optimization Procedure ◽  
Powdered Material ◽  
Extrusion Process ◽  
Die Design ◽  
Experimental Procedure ◽  
Extrusion Die ◽  
Powdered Coal ◽  
Good Agreement

Abstract This paper presents a one-dimensional analytical model of the ram extrusion process of a powdered material and a procedure for optimizing the shape of the extrusion die. Powdered coal mixed with water and asphalt was used as the extrudate material in the model development. The analytical model relates the pressure at the entrance of the die to the exit pressure of the die. Certain key parameters of the model were obtained from experiments. The comparison of the inlet pressure derived from the analytical model and the value obtained from the experimental procedure shown a good agreement. Optimization algorithms were applied to generate the ideal die shape. The objective is to minimize the power consumed in the extrusion process, while maintaining maximum strength for the extrudates. It is concluded from the study that the model and the optimization procedure developed for the model can be used in extrusion studies of other powdered materials.

Experimental Study of Propeller-Induced Vibratory Pressures on Simple Surfaces and Correlation With Theoretical Predictions

1964 ◽  
Vol 8 (05) ◽  
pp. 15-28
Author(s):  
J. P. Breslin ◽  
T. Kowalski
Keyword(s):  
Free Space ◽  
Three Dimensional ◽  
Theoretical Treatment ◽  
Plate Boundaries ◽  
Practical Application ◽  
Finite Area ◽  
Experimental Procedure ◽  
Theoretical Predictions ◽  
Pressure Changes ◽  
Good Agreement

Vibratory pressures exerted on cylindrical and flat-plate boundaries due to a model propeller were measured at three advance coefficients. A number of "free-space" measurements also were made. All measurements were made by driving a propeller past fixed pressure gages. This method yielded curves of pressure changes which are entirely free from background noise. The magnitudes of the free-space pressures were found to be larger than one half the corresponding magnitudes measured by gages mounted flush in a large plate at equal clearances from the propeller. By postulating that the finite area of the gage diaphragm produces a partial image of the propeller (and hence a larger pressure than that in free space) an experimental procedure was devised for correcting for this finite-area effect yielding results in good agreement with theory. A theoretical treatment of this effect of finite gage size is given in Appendix 2. The decay of maximum amplitudes of vibrating pressures is shown by means of three-dimensional plots. The pressures were found to become vanishingly small within approximately one propeller diameter fore and aft of the center of the propeller. The comparison with theoretically calculated pressures and forces gives very close agreement for free-space pressures and reasonable agreement for forces on a cylindrical surface. The agreement of both pressures and forces with theory is excellent for operation near the design advance ratio. A strong plea is made for further experiments with ship models in an effort to develop design criteria for practical application.

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