Calculation Of Transfer Coefficient Research Articles

Determination of the 137Cs and 90Sr radioisotope activity concentrations found in digestive organs of sheep fed with different feeds

In this study, 12 weanling lambs were fed for 6 months at the Vetenary Control and Research Institute of Elazığ in Turkey. Sheep were divided into two groups according to feeding type. Each group of sheep was fed a different amount of feed. The activity concentrations of 137Cs and 90Sr were determined in rumen, small intestine and large intestine tissue samples of sheep fed various feeds and quantities.Transfer coefficients and concentration ratios were estimated. The highest average 137Cs and 90Sr activity concentrations were 82 ± 22 Bq kg−1 fw in the straw group small intestine sample and 74 ± 9.0 Bq kg−1 fw in the fresh lucerne group rumen sample, respectively. Radioactivity levels for 137Cs and 90Sr are under the maximum permitted radioactive pollution level for all the samples. The transfer coefficient of 137Cs and 90Sr in the samples of sheep ranged from 1.0 × 10−1 to 2.1 × 100 d kg−1 and 1.7 × 10−1 to 2.3 × 100 d kg−1, respectively. Calculated transfer coefficients of 90Sr and 137Cs in the samples of sheep were higher than the expected values. Geometric means of Ff and CR for 137Cs were maximum in the fresh lucerne group large intestine sample. Geometric means of Ff and CR for 90Sr were maximum in the fresh lucerne group small intestine sample.

Achieving a Specific Nonuniform Heat Flux With an Electrical Heat Flux Plate

A voltage applied across a uniform plate results in a uniform ohmic heat dissipation, useful for conducting heat transfer experiments or preventing unacceptably low temperatures on spacecraft components. Most experiments to date involve application of a known uniform heat flux to the surface of a model. Measurement of the resulting temperature distribution facilitates calculation of the heat transfer coefficient, h. The dependence of h on the boundary condition, however, may necessitate a specified nonuniform heat flux. In this paper, a novel methodology is developed for designing a nonuniform thickness heat flux plate to provide a specified spatially variable heat flux. The equations are derived to solve the two dimensional heat flux with a variable cross sectional area. After showing that this inverse heat transfer problem cannot be readily linearized, a methodology utilizing a smooth surface polynomial was applied. Then, for a prescribed, desired heat flux distribution, a 7th order polynomial (including 36 terms) yielded a normalized root mean squared error of 1% over the surface. This distributed heat flux could result in significant power and thus cost savings for a variety of applications.

Liquid–Liquid Test Reactions to Characterize Two-Phase Mixing in Microchannels

Multiphase flow is often found in chemical engineering, food processing, or analytical devices. First contacting and droplet generation as well as coalescence and redispersion are important for the flow characteristics. In all processes, the channel geometry, fluid properties, and flow velocity determine the flow regime, droplet size, and interfacial area. The hydrolysis of alkyl acetates in organic phase with sodium hydroxide NaOH in the aqueous phase is investigated as flexible test reaction for mass transfer and interfacial area determination. The alkyl group is chosen from ethyl, isopropyl, or n-butyl, which differ in water solubility, diffusivity, and rate constant, for adequate design of the characteristic time for mass transfer. The consumption of NaOH is used for calculation of specific area and related mass transfer coefficient. Different channel geometries are characterized and design considerations are derived.

Hydrodynamics and mass exchange in gas-liquid slug flow in microchannels

The present state of hydrodynamics and mass transfer studies in segmented gas-liquid flow in microchannels has been analyzed. It has been shown that such parameters as gas bubble velocity, gas hold-up, relative gas bubble length, pressure drop, mass transfer coefficients from gas bubbles to liquid slugs and to liquid film, as well as mass transfer coefficient from liquid to channel wall can be satisfactorily predicted. Nevertheless, some correlations were obtained under definite conditions and should be summarized. The purpose of further research is to develop reliable methods for calculation of mass transfer coefficients as functions of channel geometry, phase properties, and phase velocities in mini- and microchannels.

Study on transfers of uranium, thorium and decay products from grain, water and soil to chicken meat and egg contents

Activity concentrations of the uranium and thorium series radionuclides were determined in chicken meat and eggs as well as in soil, water and other dietary intakes of poultry at five sites of the French territory. These data allow the calculation of transfer coefficients which enrich the database given by the technical report series no. 472 of the IAEA. In egg contents, the highest activity concentrations (in mBq kg(-1) fresh weight) are for (226)Ra, ranging between 136 and 190 and are much lower for uranium (between 0.51 and 1.30 for (238)U). In chicken meat, (238)U activity concentration is higher than in egg contents and ranges between 1.7 and 9.7. Concerning (232)Th, its activity concentration is lower than uranium and ranges between 0.5 and 4.9. Daily ingested activity concentration by the animals was assessed taking into account the activity concentrations measured in the grains, in the soil and in the drinking water. The activity concentration in grains and the daily intakes allow the calculation of concentration ratios and transfer coefficients for chicken meat and egg contents. In chicken meat the transfer coefficients (d kg(-1)) range between 0.0018 and 0.0073 for (238)U and between 0.0008 and 0.0028 for (232)Th. In egg contents they range from 0.00018 to 0.0018 for (238)U and are much higher for radium isotopes (0.10-0.23 for (226)Ra and 0.07-0.11 for (228)Ra).

Simulation of MEG Packed Distillation Column Using an Equilibrium Stage Model–Case Study on Operating Parameters of Farsa Petrochemical Company–Assaluyeh–Iran

Abstract Two types of equilibrium and non–equilibrium stage models are generally used to simulate the mass transfer of packed distillation column. Using non–equilibrium model requires the calculation of mass transfer coefficients, thus, usually equilibrium–based methods are preferred to be used for simulations of distillation columns. In this paper, packed column distillation of production of Mono Ethylene Glycol in FARSA SHIMI Company (Assaluyeh –Iran)’s Ethylene Glycol portion has been simulated through using the equilibrium model and solving the related equations. The simulation has been carried out in the MATLAB environment. The column also has been simulated in the Aspen Hysys and Aspen Plus ver.2006.5 environments. Then, the output has been compared with software results, designing and operating data of the underlying columns which demonstrate good consistency with the model. Having the model validated, the effect of some operating parameters has been analyzed through the model.

Extractive distillation modeling of the ternary system 2-methoxy-2-methylpropane-methanol-butan-1-ol

AbstractInfluence of model complexity on the separation equipment performance was investigated. As an example, separation of azeotrope formed by 2-methoxy-2-methylpropane and methanol was considered using butan-1-ol as an extractive solvent. Non-equilibrium model of a column for extractive distillation accounting for the mass and heat transfer rates was composed according to the rigorous Maxwell-Stefan theory. An empirical AICHE correlation was adopted for the calculation of binary mass transfer coefficients at column trays. Results of the column steady-state operation were compared with those obtained assuming different equilibrium models. Effect of the quality of the vapor-liquid equilibrium (VLE) description on the results of the separation simulation considering real behavior of either liquid or both equilibrium phases was tested. Real behavior of the liquid phase was computed according to the NRTL equation taking into account binary and, in some cases, also ternary equilibrium data. In case of real behavior of the vapor phase, the equation of state in the form of virial expansion was employed. Qualitative agreement was found comparing the simulation results calculated by equilibrium and non-equilibrium models of the extractive distillation column while using the same description of ternary VLE.

Research on Pipe-Soil Displacement Transfer Coefficient for Buried Pipeline

In anti-seismic design of buried pipeline, selection of pipe-soil displacement transfer coefficient is the decisive factor for reasonable and stable analysis on seismic damage. This paper discusses calculation and selection of pipe-soil displacement transfer coefficient and related parameters, gives more definite, reasonable, simple, and reliable method of determination incorporating with existing achievements for analysis on seismic damage to buried pipelines. The results of analysis provide for anti-seismic design of buried pipelines with basis of reference.

A Research of Apparatus and Optimal-Control Theory on Precision Seeding in Forestry

After analyzing and studying the existing sowing operation in forestry, a set of technological process of precision seeding based on optimal-control theory has been put forward and the prototype has also been designed and produced. This paper presents the general structure of the apparatus and analyses the working principle. An adjustable cell wheel feeding apparatus is designed to solve the problem of the uniformity of seeding. The theories of cooling mulching without adhesive on nutrition membrane and the process of membrane mulching are analyzed to set up the pressure model of the roll. After the experiments on the pressure of the roll and the analysis of the data, by the calculation of axial pressure transfer coefficient of the roll, has determined the best pressure of membrane mulching. At last, the test conditions of the prototype show that the frequency of failures is decreased, the damage rate of seeds is reduced, the seeding precision is improved, which satisfy the requirements of technical regulation on seeding in forestry and is beneficial to improve utilization ratio of good seeds.

Boiling Heat Transfer on Small Diameter Tube Bundle

An experimental study has been carried out using a tube bank representing a section of a tube bundle. The bank comprised 3 columns each of 10 stainless steel electrically heated tubes of 3mm outside diameter with pitch to diameter ratio of 1.5 in an in-line arrangement. Flow rate through the test section was controlled. Each tube in the central column was instrumented to permit determination of the tube temperature and heat flux, hence permitting calculation of the heat transfer coefficient. These tests were carried out using distilled water at nominal atmospheric pressure over a range of heat fluxes between 6 - 21 kW/m2. Results of the heat transfer tests are presented and compared with correlations used for conventionally sized bundles. Correlations developed for large tube bundle overestimate the experimental results.

FREQUENCY PROPERTIES OF THE NON-HOMOGENEOUS PERIODICAL LINE

Frequency properties of the non-homogeneous periodical line are analyzed. The model of the signal path containing the non-homogeneous periodical line is presented. The programs for calculation of line input impedance and transfer coefficient were developed. Calculation results are presented and analyzed. They show that the stop–band appears due to periodical inhomogeneities. Its central frequency depends on the length of the period of the line. The width of the stop–band and the attenuation in it depend on intensities of periodical inhomogeneities.

Comparing different methods of analysing sewage sludge, dewatered sewage sludge and sewage sludge ash

The following article compares different ways of characterising sewage sludge. Against the background of sludge recycling in agriculture as well as treatment with subsequent phosphorus recovery in mind, the article starts by collating and evaluating the levels of phosphorus, heavy metals, chlorine and sulphur in sludge as reported in the literature. Sewage sludge from the sewage treatment plant at Kaditz in Dresden was analysed using standardised and adjusted methods, which produced different results. In the course of this analysis the results were produced by using elemental analysis, atomic absorption spectroscopy, X-ray fluorescence spectroscopy (X-RFA) and ion chromatography (IC). The second part of the article therefore seeks reasons for the differences in the findings and tries to give solution statements. The article closes by calculating transfer coefficients for selected parameters during the incineration process and solid–liquid separation and weighing up the analysis techniques compared. Basically this article will show significant differences in sludge composition and the effects on the specific elements by ashing or mechanical dewatering of the different sludges. An essential attention obtains the analysis by using the X-RFA.

Thermofluid-Dynamic Analysis of Circular-Planar Type Intermediate-Temperature Solid Oxide Fuel Cells

This work presents a computational thermofluid-dynamic analysis of circular-planar type intermediate-temperature solid oxide fuel cells (SOFCs), based on the Hexis design. A single cell, representative of the average conditions of a real stack, is simulated in detail considering the real anode and cathode channel design, featuring an array of square pegs supporting the interconnection layers. The analysis is developed starting from cell operating data assumed from real test experimental information for an anode-supported SOFC with a 100cm2 active area, fed with pure hydrogen, and is extended to different reactant flow rates and generated heat flux power densities to evidence a generalized correlation for the thermofluid-dynamic behavior of the fuel cell under variable operating conditions. Aiming to provide a set of general results for the calculation of the heat transfer coefficient, which is applicable for the purpose of a complete thermal and electrochemical finite volume analysis, the simulation calculates local temperature distributions depending on radial and angular positions. The fluid-dynamic analysis evidences the existence of preferential flow paths and nonuniformity issues of the gas flow field, which may affect significantly the cell performances, and indicates possible cell design improvements.

Separation of strontium from calcium by the use of sodium hydroxide and its application for the determination of long-term background activity concentrations of 90Sr in 100 km area around Kozloduy Nuclear Power Plant (Bulgaria)

The method for the determination of 90 Sr which employs sodium hydroxide for the separation of strontium from calcium was further improved introducing the use of elevated temperatures. The results from 11-year study of background activity concentrations of 90 Sr in different environmental objects in 100 km zone around Kozloduy Nuclear Power Plant (Bulgaria) are presented as an application of the analytical method. The measured mean values are as follows: air precipitation – 0.0015±0.0009 Bq/(m 2. d), tap water – 0.0017±0.0012 Bq/L, soil – 1.90±1.26 Bq/kg, grass – 1.54±0.80 Bq/kg, milk – 0.023±0.012 Bq/L and for the Danube river: water – 0.0046±0.0026 Bq/L, bottom sediments – 0.64±0.60 Bq/kg, algae – 1.99±1.56 Bq/kg. The calculated transfer coefficients (soil-grass) are in the range of 0.33–0.84. Between 2 and 5 times reduction in actual background activities of 90 Sr is observed compared to 1972–1974.

Radon transfer from groundwater used in showers to indoor air

Abstract Estimation of Rn transfer from water to indoor air based on multi-day measurements may underestimate alpha exposure that occurs at short time scales in confined spaces, such as from showering, in houses with high Rn activities in the water supply. In order to examine one such incremental increase in exposure, variations in Rn in water and indoor air in 18 houses with private wells in western North Carolina (USA) were investigated. Radon in well water ranged from 158 to 811 Bq L −1 (median 239 Bq L −1 ). After 20-min showers in bathrooms with closed doors, peak Rn in air increases (above background) ranged from 71 to 4420 Bq m −3 (median 1170 Bq m −3 ). Calculated transfer coefficients at the scale of a 40-min closed bathroom (20-min shower plus 20 min post-shower) are described by a lognormal distribution whose geometric mean exceeds the widely-used ∼10 −4 whole-house transfer coefficient by about one order of magnitude. As short-lived decay products grow from shower-derived Rn, short-term alpha energy exposure occurs in bathrooms in addition to the exposure caused by Rn mixed throughout the volume of the house. Due to the increasing ratio of Rn decay products to Rn, alpha energy exposure is greatest several minutes after the shower is turned off. For a 7.2-min shower with 10 min of additional exposure before opening the door, a geometric mean 5.6% increase in exposure over the ∼10 −4 whole-house transfer coefficient derived from longer measurement periods was estimated. In addition to Rn activity in water, short-term shower exposure to Rn progeny depends on exposure time, ventilation, attachment and deposition, among other variable factors that characterize individual houses and residents.

Calculation of Gas Carburizing Kinetics from Carbon Concentration Profiles based on Direct Flux Integration

Initiated by the need of industry for gas carburizing process control and optimization, this paper focuses on understanding the effect of the time, temperature and carbon potential on the mass transfer coefficient and carbon diffusivity in Austenite. A method for direct flux integration has previously been proposed to calculate these kinetic parameters from the experimental carbon concentration profiles. AISI 8620 steel discs were gas carburized at different levels of atmosphere carburizing potential for selected austenizing temperatures. Analyses of the carburized parts included experimental measurement of weight gain, surface carbon concentration and carbon concentration profiles. The time-dependent weight gain and surface carbon content measurements allowed calculation of the time average mass transfer coefficient, while carbon concentration profiles were used to calculate the concentration dependent carbon diffusivity for selected process parameters. Excellent agreement was found between the calculated mass transfer coefficient and carbon diffusivity values and those reported in the literature. The calculated values served as input in the previously developed carburizing model validating the predicted results by comparison with the experimental concentration profiles.

Osmotic Dehydration/Impregnation Kinetics of Padrón Pepper (Capsicum annuum L. Longum) with Sodium Chloride Solutions: Process Modelling and Colour Analysis

Experimental determinations were carried out to evaluate the dehydration/impregnation mass transfer rates that take place during osmotic processing of Padrón peppers ( Capsicum annuum L. var. Longum) with sodium chloride solutions. Several sodium chloride concentrations (from 17 to 26.5% w/w) and temperatures (from 25 to 45°C) and contact times (up to 8h) were selected as variables. Solids gain, weight reduction, water loss, normalised moisture content and normalised solids content were calculated at each experimental condition. These data allowed the calculation of water and salt mass transfer coefficients for modelling the corresponding kinetics. Additionally, pepper colour changes during osmotic contact at different experimental conditions were determined. In all cases, solids gain, weight reduction and water loss increased with temperature and salt concentration. Water loss values are low and water loss/salt gain ratio is also low (as it is usual when sodium chloride solutions are employed as osmotic media). In this way, osmotic process can be basically considered as an impregnation process. In all experimental conditions the colour changes were only significant at the highest temperature assayed and also depended on osmotic concentration.

Mass Transfer Modeling with and Without Evaporation for Iodine Chemistry in the Case of a Severe Accident

Iodine is a fission product of major importance in a severe reactor accident because volatile species exist under reactor containment conditions. Radiolytic oxidation of iodide ions is an important source of volatile iodine species. The SISYPHE tests provide an experimental database of prime importance for the study of the mass transfer between the sump and the atmosphere of a containment building under natural convection and in an evaporating flow regime. This phenomenon greatly impacts the airborne iodine concentrations. The two main effects of evaporating conditions are to increase the kinetics of transfer from the liquid to the gaseous phase and to change the steady-state iodine concentrations. The well-known two-film model has been modified to extend to these types of conditions. The agreement between the experimental results and modeling is satisfactory. However, when applied to typical reactor conditions, the impact of this improved modeling on gaseous iodine concentration is not as strong as other phenomena; for example, uncertainties remain concerning organic iodide production mechanisms. Correlations enabling the calculation of individual mass transfer coefficients for the liquid and the gas phases are proposed. The values resulting from these correlations agree well with those obtained from the test interpretations.

Dislodgeable foliar residues are lognormally distributed for agricultural re-entry studies.

The Agricultural Reentry Task Force (ARTF) conducted a study to determine if dislodgeable foliar residues (DFR) are either normally or lognormally distributed. This is important because the data are used with worker exposure data, which generally appear to be lognormally distributed, to calculate transfer coefficients that will be used to assess farm worker re-entry exposure. Two chemicals were used for this study. Carbaryl, a moderately water-soluble chemical, was applied to cabbage at a rate of 2.0 lbs active ingredient/acre (lb ai/A), while methomyl, a highly water soluble chemical, was applied to cabbage at a rate of 0.9 lb ai/A. The residues were dislodged following an ARTF standardized procedure of collecting leaf punches and shaking in a solution of 0.01% Aerosol OT 75. A total of 28 samples were analyzed for each chemical. The mean+/-SD residue of the carbaryl samples was higher than that for methomyl (511+/-196 and 170+/-71 mug per sample, respectively). However, several types of statistical analyses of the data indicated that, for both chemicals, the residues are lognormally distributed.

Response to comments on “Calculation of wall conduction transfer coefficients by regression in the frequency domain”

Response to comments on “Calculation of wall conduction transfer coefficients by regression in the frequency domain”