Measurement of discharge rate in a canal using radiotracer dilution technique

Measurement of discharge rates of fluids and solids is an essential requirement in industrial and environmental systems. Radiotracer techniques are widely used for measurement of fluids/solids in situations where conventional techniques cannot be applied. The present paper describes application of radiotracer dilution technique to measure the discharge rate of water in a canal with an objective to validate efficiency of the Concrete Volute Pump used for pumping water in the canal. ¹³¹I radioisotope having activity of 55.5 GBq was used as radiotracer. The discharge rate of water was measured to be 20.6 m³/s.     

Mixing characterization in batch reactors using the radiotracer technique

The infusion rate of a slug of tracer into an anchor agitated 100-liter batch mixer was characterized by a decay rate constant. This constant was then used to define a dimensionless mixing-rate number which was related to the stirrer Reynolds number. This correlationship allows the calculation of time or rotational speed needed to achieve any desired degree of uniformity of the mixture.^99mTc was used as radiotracer and the mixing process was followed by a scintillation Nal(Tl) counter situated on the reactor wall near the injection point.     

Sorption of hafnium on hydrous titanium oxide using radiotracer technique

The sorption of hafnium on hydrous titanium oxide (TiO₂·1.94 H₂O) has been studied in detail. Maximum sorption of hafnium can be achieved from a pH 7 buffer solution containing boric acid and sodium hydroxide using 50 mg of the oxide after 30 minutes shaking. The value ofk _d, the rate constant of intraparticle transport for hafnium sorption, from 0.01M hydrochloric and perchloric acid and pH 7 buffer solutions has been found to be 17 mmole·g^–1·min^–2. The kinetics of hafnium sorption follows Lagergren equation in 0.01M HCl solution only. The values of the overall rate constantK=6.33·10^–2 min^–1 and of the rate constant for sorptionk ₁=6.32·10^–2 min^–1 and desorptionk ₂=2.28·10^–5 min^–1 have been evaluated using linear regression analysis. The value of correlation factor() is 0.9824. The influence of hafnium concentration on its sorption has been examined from 4.55·10^–5 to 9.01·10^–4 M from pH 7 buffer solution. The sorption data followed only the Langmuir sorption isotherm. The saturation capacity of 9.52 mmole·g^–1 and of a constant related to sorption energy have been estimated to be 2917 dm³·mole^–1. Among all the additional anions and cations tested only citrate ions reduce the sorption significantly. Under optimal experimental conditions selected for hafnium sorption, As(III), Sn(V), Co(II), Se(IV) and Eu(III) have shown higher sorption whereas Mn(II), Ag(I) and Sc(III) are sorbed to a lesser extent. It can be concluded that a titanium oxide bed can be used for the preconcentration and removal of hafnium and other metal ions showing higher sorption from their very dilute solutions. The oxide can also be employed for the decontamination of radioactive liquid waste and for pollution abatement studies.     

Residence time distribution measurements in an ethyl acetate reactor using radiotracer technique

Journal of Radioanalytical and Nuclear Chemistry - In the present study, residence time distribution measurements were carried out in an industrial-scale ethyl acetate reactors using Bromine-82 as...     

Measurement of circulation rates of coal particles in standpipe of a circulating fluidized bed system (CFBS) using radiotracer technique

Radiotracer technique was applied to measure the circulation rates of fine coal particles in standpipe of a pilot-scale bubbling circulating fluidized bed system (CFBS). ¹⁹⁸Au adsorbed on coal particles was used as a radiotracer. The radiotracer was injected into the standpipe and monitored at four different downstream locations. The circulation times and circulation rates were determined from the measured tracer concentration curves at different operating conditions. The measured parameters were intended to be used for optimizing the performance of existing CFBSs operating in industry and design of a new CFBS to be used as coal gasifier.     

Experimental investigation of heat transfer and exergy loss in heat exchanger with air bubble injection technique

Journal of Thermal Analysis and Calorimetry - The main aim of this study is to evaluate thermal performance and exergy analysis of a shell-and-tube heat exchanger with a new technique called air...     

CFD analysis for thermo-hydraulic properties in a tubular heat exchanger using curved circular rings

Journal of Thermal Analysis and Calorimetry - The never-ending demands of humans have led researchers to find more efficient energy conversion technologies. Enhancing heat transfer rate in a...     

Determination of131I in soil using a liquid anion exchanger and liquid scintillation technique

A simple method for rapid determination of¹³¹I in soil is described. The method is based on the specific separation and concentration of radioiodine from the soil extract with a liquid anion exchanger and measuring its radioactivity with liquid scintillation counting. The¹³¹I from soil is extracted with aqueous solution of sodium hydroxide. The method permits the determination of¹³¹I with a lower limit of detection less than 0.1 Bq/10 g of soil.     

Thermodynamic evaluation of heat recovery through a Canopus heat exchanger for vapor compression refrigeration (VCR) system

This communication deals with the waste heat recovery from the industrial refrigeration and air-conditioning system by introducing Canopus heat exchanger. There is a considerable amount of low-grade heat available in large-capacity systems. To recover this low-grade heat, a Canopus heat exchanger is introduced between compressor and condenser components. The system feasibility is studied with various operating parameters and its effect on heat recovery factor and overall COP of the system. The parametric results obtained for different eco-friendly working fluids, such as R-134a and R-507a, have been presented. It is found that, in general, overall COP of the system is improved without affecting the actual performance of the system. The potential of low-grade heat availability is increased with increasing cooling capacity.     

Investigation of leaching of an antifouling agent from marine paint formulations using radiotracer technique

A radiotracer technique was used to investigate the leaching of an antifouling agent from different marine paint formulations with an objective to select the best paint formulation for bulk production. The antifouling agent (Diuron) itself was labeled with carbon-14 (half-life: 5,730?years, ??-energy: 156?keV) and used as a radiotracer. The different paint formulations added with radiolabeled Diuron were applied onto suitably selected substrates and measured for initial intensity of ??-radiation using a Geiger-Muller detector connected to a ratemeter. The painted substrates were subjected to shower tests for a pre-decided time and subsequently measured for ??-radiations. The comparison of intensity of ??-radiations in substrates prior and post shower tests provides information about leaching of antifouling agent Diuron from the paint formulation. The high leaching percentage of antifouling agent Diuron post shower tests indicates non-suitability of paint formulation for marine and civil structures. However, low leaching rate of Diuron will make a paint formulation more efficient and suitable. Based on the results of investigation, a paint formulation with minimum leaching rate was identified and selected for bulk production by a paint company.     

Development of 99Mo-alfa-benzoin oxime complex as industrial radiotracer for identification of leaky heat exchanger and its validation with 99mTc

Journal of Radioanalytical and Nuclear Chemistry - In the traditional medicine of Iran, some herbal medicines are used for treating of high blood sugar. In this study, the concentration of Ca, Cr,...     

Three-dimensional numerical simulation of external fluid flow and heat transfer of a heat exchanger in a wind tunnel using porous media model

Journal of Thermal Analysis and Calorimetry - Notwithstanding the widespread use of wind tunnel to investigate the performance of radiators and heat exchangers, has never been considered a...     

Investigation of chlorophylls as a scavenger of manganese(II) and zinc(II) using a radiotracer technique

Uptake of manganese(II) and zinc(II) by chlorophylla (Chl) was investigated using a radiotracer technique in order to elucidate its ability of scavenging metals released into the soil environment. Two possibilities were considered for the metal uptake: (1) substitutional complexation with Chl and (2) inclusion of the metals into Chl aggregates. It was found that manganese(II) was not trapped appreciably by both Chl itself and its aggregates. Magnesium of Chl was exchanged with zinc(II) in aqueous phase giving Zn−Chl at pH values higher than 7. Zinc(II) was found to be trapped by Chl aggregates depending on the pH of the aqueous phase.     

Investigation of hydrodynamic behaviour of a pilot-scale trickle bed reactor packed with hydrophobic and hydrophilic packings using radiotracer technique

A radiotracer study was carried out in a trickle bed reactor (TBR) independently filled with two different types of packing i.e., hydrophobic and hydrophilic. The study was aimed at to estimate liquid holdup and investigate the dispersion characteristics of liquid phase with both types of packing at different operating conditions. Water and H₂ gas were used as aqueous and gas phase, respectively. The liquid and gas flow rates used ranged from 0.83?×?10^?7?C16.67?×?10^?7?m³/s and 0?C3.33?×?10^?4?m³ (std)/s, respectively. Residence time distribution (RTD) of liquid phase was measured using ⁸²Br as radiotracer and about 10?MBq activity was used in each run. Mean residence time (MRT) and holdup of liquid phase were estimated from the measured RTD data. An axial dispersion with exchange model was used to simulate the measured RTD curves and model parameters (Peclet number and MRT) were obtained. At higher liquid flow rates, the TBR behaves as a plug flow reactor, whereas at lower liquid flow rates, the flow was found to be highly dispersed. The results of investigation indicated that the dispersion of liquid phase is higher in case of hydrophobic packing, whereas holdup is higher in case of hydrophilic packing.     

Investigations on surface diffusion in sparingly soluble monolayers at the gas/liquid interface using radiotracer technique

Summary A method is proposed for calculating surface selfdiffusion coefficients in sparingly soluble monolayers at fluid interfaces based on radiotracer measurements and allowing for counter geometry. On this basis an analysis of experimental results is possible without having to allow for processes competing with surface self-diffusion. Monolayers of various long-chainn-alcohols andn-alkane-carboxylic acids were studied in the area range between 0.23 nm²/molecule and 2.0 nm²/molecule. Surface self-diffusion coefficientsD _s were determinded only up to areas of 0.75 nm2/molecule since, in case of greater areas, the analysis of surface concentration becomes inexact due to the increasing influence of density convection. For the systems studied,D _s values lie in the order of 10^–5 cm²/s. In all compounds studied, the values ofD _s increase with area per molecule. In addition, dependence on the type of hydrophilic group and alkyl-chain length of monolayer molecules was proved. The results are discussed by means of various model concepts.

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Zusammenfassung Ein Verfahren zur Berechnung der Oberflächenselbstdiffusionskoeffizienten in schwerlöslichere Monoschichten an fluiden Phasengrenzen auf der Grundlage von Radiotracermessungen und unter Berücksichtigung der Zählrohrgeometrie wird vorgeschlagen. Auf dieser Basis ist eine Auswertung der Experimentalergebnisse möglich, ohne daß zur Oberflächenselbstdiffusion in Konkurrenz stehende Transportvorgänge berücksichtigt werden müssen. Untersucht wurden Monoschichten verschiedener längerkettigern-Alkanole undn-Alkancarbonsäuren im Flächenbereich zwischen 0,23 nm²/Molekül und 2 nm²/Molekül. OberflächenselbstdiffusionskoeffizientenD _s wurden nur bis zu Flächenwerten von 0,75 nm²/Molekül bestimmt, weil bei höheren Flächen die Auswertung der Oberflächenkonzentrationsänderungen wegen des zunehmenden Einflusses von Dichtekonvektion ungenau wird. DieD _s -Werte liegen für die untersuchten Systeme in der Größenordnung 10^–5 cm2/s. Bei allen untersuchten Verbindungen nehmen die Werte von D_s mit steigender Fläche pro Molekül zu. Außerdem wurde die Abhängigkeit von der Art der hydrophilen Gruppe und der Alkylkettenlänge der Monoschichtmoleküle nachgewiesen. Die Ergebnisse wurden anhand verschiedener Modellvorstellungen diskutiert.

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With 8 figures and 1 table     

Investigations on surface diffusion in sparingly soluble monolayers at the gas/liquid interface using radiotracer technique

Summary For creating favourable conditions for the experimental proof of surface-diffusion processes in sparingly soluble monolayers at the gas/liquid interface by means of radiotracer technique, possible factors of influence such as evaporation, desorption and convection were studied. From radiotracer measurements it followed that the share of evaporation and desorption in case of long-chained n-alkanols and n-alkane-carboxylic acids can be neglected. Even at correct experimental setup long-term movements of monolayer material occurred which, on the one hand, induced a lateral shifting of the boundary labelled/non-labelled, on the other a wavelike distribution of the monolayer material which initially had a statistically homogeneous distribution. The analysis of possible mechanical and thermal causes showed that these phenomena can be explained only by temperature-induced density instability in the volume phase of the trough. On this basis a model is proposed which explains the formation of compressed and expanded areas of monolayer material.

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Zusammenfassung Zur Schaffung günstiger Bedingungen für den experimentellen Nachweis von Oberflächendiffusionsvorgängen in schwerlöslichen Monoschichten an der Phasengrenze Gas/Flüssigkeit mit Hilfe der Radiotracertechnik wurden mögliche Einfluggrößen, wie Verdampfung, Desorption und Konvektion, untersucht. Aus Radiotracermessungen resultierte, dag der Anteil von Verdampfung und Desorption bei langkettigenn-Alkanolen undn-Alkansäuren vernachlässigt werden kann. Auch bei einwandfreier Versuchsdurchführung traten langzeitige Bewegungen des Monoschichtmaterials auf, die einmal zur lateralen Verschiebung der Grenze markiert/nichtmarkiert, zum anderen zur wellenförmigen Umverteilung des anfangs statistisch homogen verteilten Monoschichtmaterials führten. Die Analyse möglicher mechanischer und thermischer Ursachen ergab, daß diese Erscheinungen nur durch temperaturbedingte Dichteinstabilität in der Volumenphase des Troges erklärt werden können. Auf dieser Basis wird ein Modell vorgeschlagen, das die Ausbildung komprimierter und expandierter Bereiche des Monoschichtmaterials erklärt.

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With 6 figures and 1 table     

Optimization of the finned double-pipe heat exchanger using nanofluids as working fluids

Journal of Thermal Analysis and Calorimetry - The heat exchanger pipe diameter has a significant effect on the flow characteristics as well as on the initial investment, operation and overall cost....     

Effective waste heat recovery from engine exhaust using fin prolonged heat exchanger with graphene oxide nanoparticles

Waste heat recovery is an important alternative to reduce the energy consumption in industrial processes. Heat Exchangers are used effectively for heat recovery. Thus, the role of heat exchangers for waste heat recovery system is crucial. The exclusive of heat transmission of a heat exchanger can be improved by many methods such as by modifying the geometries and using nano-additives of different concentration. In this continuation, a modified geometry of finned heat exchanger is developed with CFD analysis. Modified heat exchanger includes the fins in the internal pipe to improve heat transfer. Nanoparticles of graphene oxide with various concentrations are introduced in working fluid. A steady numerical study is performed by using ANSYS Fluent with k-omega turbulence model for exhaust flow. Variation at inlet velocities of exhaust gas and water, particles concentration and internal fin geometry are considered. The reduction in hot fluid temperature from 6 m/s to 2 m/s enhanced the effectiveness by approximately 33.3%. The decrease in hot fluid velocity to 2 m/s and 6 m/s can reduce its outlet temperature by 100 K and 14 K at 0.03 m/s cold fluid temperature. The inclusion of nanoparticles at 0.1% can enhance the effectiveness by maximum of 7%.     

Kinetic study of ethylene polymerization with chromium oxide catalysts by a radiotracer technique

The quenching of polymerization with a chromium oxide catalyst by radioactive methanol ¹⁴CH₃OH enables one to determine the concentration of propagation centers and then to calculate the rate constant of the propagation. The dependence of the concentration of propagation centers and the polymerization rate on reaction time, ethylene concentration, and temperature was investigated. The change of the concentration of propagation centers with the duration of polymerization was found to be responsible for the time dependence of the overall polymerization rate. The propagation reaction is of first order on ethylene concentration in the pressure range 2–25 kg/cm². For catalysts of different composition, the temperature dependence of the overall polymerization rate and the propagation rate constant were determined, and the overall activation energy E_ov and activation energy of the propagation state E_p were calculated. The difference between E_ov and E_p is due to the change of the number of propagation centers with temperature. The variation of catalyst composition and preliminary reduction of the catalyst influence the shape of the temperature dependence of the propagation center concentration and change E_ov.