Effect of salt and aging on aqueous surfactant formulations for tertiary oil recovery: A correlation of physical properties with microstructure using spin-labels

Physical properties and molecular packing in surfactant aggregates of the surfactant formulation 5% (w/w) TRS 10–410 (a petroleum sulfonate), 3% (w/w) isobutanol and desired quantities of sodium chloride in distilled water were studied using electron spin resonance (ESR) technique and pH, density, viscosity, screen factor, specific conductance, surface tension and free sodium ion measurements of fresh and aged solutions. The results suggested that both salt concentration and aging lead to changes in molecular packing of surfactant aggregates. At optimal salinity, the order parameter was a maximum. With increasing salt concentration, the correlation time increases initially and decreases at higher salt concentration. Various physical property data substantiate the observed microstructural changes. A detailed discussion is presented of the interrelations of these parameters operative in this complex surfactant formulation. Presently with the Whiteshell Nuclear Research Establishment, Atomic Energy of Canada Ltd., Pinawa, Manitoba, Canada ROE 1LO.     

Observation of red emission in wurtzite ZnS nanoparticles and the investigation of phonon modes by Raman spectroscopy

Wurtzite ZnS nanoparticles are synthesized by a low temperature chemical method using ethylene glycol. Photoluminescence studies reveal a new red emission along with strong UV and blue emission known to occur from nanocrystalline ZnS. An energy level diagram involving oxygen trap levels and interstitial sulphur ions is proposed to explain the origin of the observed emission peaks. Micro-Raman spectroscopic studies indicate that the optic modes get softened whereas the second order longitudinal acoustic (LA) phonon mode get hardened in the nanocrystals. The analysis is done by taking into account the effect of the small particle size of nanoparticles as well as the existence of defects resulting in strain in the lattice.     

Synthesis,growth and structural perfection of nonlinear optical material of glycine hydrofluoride (GHF)

In the present communication, we have successfully synthesized the efficient NLO material of glycine hydrofluoride (GHF) by conventional chemical reaction, and grown the single crystal by adopting slow evaporation solution growth technique. In order to know its suitability for device fabrication, different characterization analyses have been performed. The lattice constants have been determined from powder X-ray diffraction (PXRD) method and found that it crystallizes in orthorhombic crystal system. Its crystalline perfection was evaluated by high-resolution X-ray diffraction technique (HRXRD) and the value of FWHM indicates the presence of low angle structural grain boundaries. Its luminescence behaviour has been analysed by photoluminescence (PL) analysis and found maximum luminescence in the lower wavelength region. Its relative second harmonic generation efficiency was evaluated from Kurtz powder technique. The phase matching angle of GHF was determined by using Nd:YAG laser as a source. Its thermal, mechanical and electrical properties were examined by TG/DTA, Vickers microhardness tester and dielectric measurements, respectively.     

Investigation on the characteristic of CHF in various flow pattern regimes based on look-up table data

The critical heat flux (CHF) is one of the important phenomena limiting the maximum rate of heat transfer and hence power rating of nuclear reactors. The thermal hydraulic phenomena like pressure drop, heat transfer, stability, etc. depends upon the flow pattern in the system. The CHF phenomenon is also closely related to the two-phase flow patterns. It is important to investigate the dependence of CHF on the flow pattern regimes to understand the underlying mechanisms. The present investigation reveals that CHF generally increases with mass flux in the churn/slug region. However, in the annular region the CHF decreases with increase in mass flux. Considering the dependency of the CHF trend on the flow pattern regime, it will be useful to develop CHF models, which are specific to the flow pattern regime. The data of CHF look-up table has been considered in this investigation since this approach is one of the most reliable methods for the prediction of CHF and is being used in several best-estimate thermal-hydraulic system codes, such as RELAP5, CATHARE and CATHENA. The pressure, mass flux and quality have been considered as important thermal hydraulic parameters to characterize the flow pattern during CHF under various operating condition.     

Combustion and heat transfer at meso-scale with thermal recuperation

Results are presented from successfully designed and fabricated meso-scale ceramic combustors that incorporate internal thermal energy recirculation. The combustor provided sustained operation using propane and air as the reactants. Flames could be obtained well below the normal quenching distance. The development required examination of several different combustor designs and materials. Flammability limits of these combustors have been determined experimentally. Experimental investigations have been performed on the effects of flame holder geometry, material conductivity, equivalence ratio, and inlet Reynolds number on the combustor performance. Measurement of the reactant preheating and product exhaust temperatures was performed using K-type thermocouples which were installed with minimal intrusion to the flow. The reactant preheating temperatures were observed to be in the range 700 K–1000 K. However, the combustor suffered significant overall heat loss (50–85%) which was implied by the low exhaust temperatures (500 K–750 K). For a constant fuel flow rate, the exhaust temperature increased monotonously with decrease in equivalence ratio until the blow-off condition implying that the combustor’s maximum thermal efficiency occurs at its lean blow-off limit. Thermal imaging of the combustor walls was performed using infrared camera to obtain the temperature distribution within the combustor. Numerical simulations were performed with the aid of CFD software using a heat loss coefficient chosen so as to give best correlation with experimental results. These CFD simulations helped to obtain better insight of the dependence of combustor performance on thermal conductivity of the material and heat load.     

Estimation of fuel and clad temperature of a research reactor during dry period of de-fuelling operation

Heat transfer and fluid flow studies related to spent fuel bundle of a research reactor in fuelling machine has been carried out. When the fuel is in reactor core, the heat generated in the fuel bundle is removed by heavy water under normal reactor operation. However, during the de-fuelling operation, the fuel bundle is exposed to air for some period called dry period. During this period, the decay heat from fuel bundle has to be removed by air flow. This flow of air is induced by natural convection only. In this period, the temperatures of fuel and clad rise. If clad temperature rises beyond a certain limit, structural failure may occur. This failure can result into release of fission products from fuel rod. Hence the temperature of clad has to be within specified limit under all conditions. The objective of this study is to estimate the clad temperature rise during the dry period.In the CFD simulation, the turbulent natural convection flow over fuel and radiation heat transfer are accounted. Standard k-? model for turbulence, Boussinesq approximation for computing the natural convection flow and IMMERSOL model for radiation are used.The steady state and transient CFD simulation of flow and heat is performed, using the CFD code PHOENICS. The steady state analysis provides the maximum temperature the clad will attain if fuel bundle is left exposed to air for sufficiently long time. For safe operation, the clad temperature should be limited to a specified value. From steady state CFD analysis, it is found that steady state clad temperature for various decay powers is higher than the limiting value. Hence transient analysis is also performed. In the transient analysis, the variation of clad temperature with time is predicted for various decay powers. Safe dry time, i.e. the time required for clad to reach the limiting value, is predicted for various decay powers. Determination of safe dry time helps in deciding the time available to the operator to drop the bundle in light water pool for storage. The analysis is found useful in optimizing the de-fuelling process.     

Expert system technology in organisational process domain modelling

Abstract: Organisational processes are repetitive, time-consuming and interdependent, requiring several members to interact for successful completion. Moreover, when organisations change their operating procedures it becomes difficult to carry out even routine tasks because of the confusion and lack of communication. By studying the organisational processes and the knowledge required to execute them, we can create generic process models that could be stored persistently in a repository. This process repository can serve as a corporate knowledge base, which could be accessed by intelligent computer assistants for automating organisational processes. This paper presents a framework of intelligent assistants that can emulate the behaviour of human agents in organisational problem-solving. The generic process models can also be customised to meet the changing needs of the organisation. We present a domain modelling approach to organisational process modelling and an expert system for customising process models. The paper also describes the architecture and design of the proof-of-concept prototype that supports organisational process modelling, as well as process execution through intelligent computer assistants.