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[en] Design and construction of An Ion Nitridation Assembly for Surface treatment of machine components by supporting budget from The Ministry of Research and Technology has been successfully performed. The utilization of this Research and Technology result in the industrial field should be lead by a Techno-Economic study to support its feasibility. The techno-economic study on the utilization of Nitridation Ion Assembly for improvement the automotive machine component surface has been carried-out. The economy or financial feasibility study covered fixed capital, working capital and break event point analysis, Payback Period and Rate of Return calculation have been finished. The result of study showed that the application of Ion Nitridation Assembly for improving the surface of automotive machine components is potential enough and has a positive prospect. For the estimation of profit by 10 % to 50 %, the Break Event Point is around 52 % to 12.9 %, or by the Payback Period around 137 months to 23.5 months. The Rate of Return analysis of the project shows that the rate of interest can he achieved by the business is 17.75 %, much greater than the rate of interest can he offered by the Bank, that is 7.2 %/year. If the rational profit 50 % is taken, the BEP of 17.9 % and Payback Period of 34.5 months are obtained, that is a good image of business. It can be concluded that Nitridation Ion Technology has a good prospect economically in business, and the technology advance be the most important factor to support the growth of economies in Small and Medium Scale National Industries. (author)
[en] As fossil fuels dominate the world primary energy supply and will do it at least for the next few decades, further improvement of the fossil-fueled power plants is needed due to many reasons, including the environmental impact and economic operation. The thermal power plants operation is commonly evaluated on a basis of the energy analysis, combustion efficiency and the level of harmful emissions generated. Often, the real useful energy loss cannot be completely justified only by the first law of thermodynamics, since it does not differentiate between the quality and amount of energy. The aim of this work is to present a methodology for analyzing opportunities for improving the efficiency of fossil fuelled steam generators, based on integration of zone thermal calculation method and exergy method, while studying the impact of such measures on the emission of nitrogen oxides. The work deals with an analysis of the energy and environmental performances of a coal-fired steam generator, which is a part of a 315 M We power generation unit. The steam generator is designed for operation on low grade coal-lignite with net calorific value in a range 6280-9211 kJ/kg, in a steam cycle at 545°C/177.4 bar, with feed water temperature 251°C. The combustion air is preheated to 272°C in two rotating air-heaters and the flue gases mean temperature at the outlet is 160°C. Since the largest exergy dissipation and losses in the thermal power plant cycle occur in the steam generator, energy and exergy balances of the furnace and heat exchanging surfaces are established in order to identify the main sources of inefficiency. The zone calculation method is used for determination of temperature profiles and heat distribution along the boiler gas path. An engineering method that considers the most influential parameters is used for estimation of the NOx emission. On a basis of the conducted analysis several opportunities for improvement are envisaged, including recirculation of flue gases, retrofitting option of lignite pre drying with flue gases and air preheating with dryer exhaust gases. (author)
[en] Highlights: • The proposed check valve has the ability of forced operation for abnormal situations. • A design concept and factors for the forced operation are described. • The effect of the proposed concept was analyzed via an example safety system (AFWS). - Abstract: Standard swing disk check valves are typically operated by pressure difference. Alternatively though, the valves might be operated by an active driving force when they cannot be operated by the pressure difference. If this simple concept is realized, the reliability of the check valve could be improved since a great portion of abnormalities currently leading to failure can be corrected. With this intention, this paper proposes a power-operated check valve and describes important factors to be considered. Through an effectiveness analysis, it was verified that the proposed concept significantly improved reliability in an example safety system.
[en] Full text: An event occurred at the Laguna Verde plant in Mexico in 2012 in which an EDG failed and caught fire, which necessitated emergency shutdown of the EDG, activation of the on-site fire brigade and actuation of automatic fire protection systems. The most probable cause was a failure of the piston bearing coating material in the internal components of the EDG. The piston bearing had a silver coating, and when this material began to degrade, the lubricating veins were also damaged; this left the material without proper lubrication. The silver coating wear caused the obstruction of a piston hole and, finally, the total loss of lubrication to power assembly cylinder 8. Some pictures from the event are shown. The EDG in question had been recently repaired on an urgent basis by an outside repair company using urgently acquired materials. The installed piston pin bearings had a slightly different design but had been acquired with the same part number. In 2014, with the unit in a refuelling outage, the evaluation to determine the apparent causes of the abnormal wear in EDG 2’s power pack piston pins determined that different materials had been used in the construction of the components installed in EDG 1–3. An extent of condition review resulted in declared inoperability of EDGs 1 and 3 and a 23 day outage extension. A result of this subsequent event was a workshop designed to create an administrative process or procedure to establish requirements for the detection and management of CFIs. These events point to the need for strict attention to detail in each stage of the procurement process and the difficulty of classifying items as non-conforming, counterfeit or fraudulent. In this case, the parts installed were clearly non-conforming to the original design (inappropriate substitutions were made) but were not necessarily intentionally installed in a fraudulent or counterfeit manner. The final classification would depend on the intent of the installation contractor, the source of the non-conforming parts and the intent of the part supplier. (author)
[en] The current study was aimed at developing a package of 'model + algorithm' for the design of resin in pulp (RIP) and carbon in pulp (CIP) processes of gold, uranium, and base metals. For this purpose, we first formulated a double-resistance model for irreversible adsorption (accompanied by chemical reaction) in CSTRs, and modified the McKay et al. semi-analytical model for reversible uptake in a similar system. We then devised two algorithms for the design and optimization of reversible and irreversible RIP and CIP cascades. The developed algorithms were applied on the extraction of copper, uranium, and gold. The packages are able to specify the optimum number of stages, reactor volume (V), resin flow rate (m.), and resin hold up (φs). This shows an evident advantage over the McCabe-Thiele method, whose only result is the number of stages. The new methods have only two adjustable parameters of diffusivity (Deff) and liquid film coefficient (k), whose determination can be carried out through simple batch experiments. As an additional work, this study also presents a method for mathematical troubleshooting for the Mc Kay et al. model. (author)
[en] Accurate prediction of interfacial drag in the downcomer annulus is crucial for the assessment of downcomer void fraction for the loss of coolant accident analysis. The downcomer annulus is the gap between reactor pressure vessel (RPV) exterior and the inner wall of pressure containment vessel (PCV). Based on the previous research, occurrence of the nonuniform two-phase flow in downcomer section is reported, which is partly due to the large wall temperature difference between RPV exterior and the inner wall of PCV. In RELAP5, interfacial drag term in downcomer section is calculated using Kataoka-Ishii and churn-turbulent drift-flux correlations. It has been pointed out that this traditional calculation approach for calculating downcomer void fraction needs modification. The purpose of the current study is to assess the behaviors of drift-flux parameters in downcomer section and to propose an improved distribution parameter model that is suitable for downcomer boiling analysis. (author)
[en] In order to understand the hydraulic characteristics of rigid cascade, the static characteristic roots were obtained by solving the perturbation equations of rigid cascades which have sonic orifice on the heavy fraction pipes. The rigid cascades only have 2 static characteristic roots. Z1 is equal to 1, and Z2 is the main static characteristic root and can be used to predict the stability of the cascade. When centrifuge works at rated condition, the main static characteristic root is greater than 1. If any centrifuge is in a stage fail, the fluid parameters can be obtained by solving perturbation equations. The analytic solution can be used to predict the changing trend of fluid parameters if the cascade is disturbed. Although the main static characteristic root is greater than 1, as the disturbances propagate to the waste end, the rigid cascade can maintain the stability. (authors)
[en] The acceptance integral approach is applicable for calculating the root mean square of structure response under random loading. The theoretical basis and application conditions of the acceptance integral approach were studied, and the approach was combined with the finite element method to simplify the calculation process and also make it easy to implement. The flow-induced vibration responses of the core barrel were calculated using the combined method and the test values of the fluid fluctuating pressure of scaled model test of core barrel. The calculation results are consistent well with the test ones. (authors)
[en] Frictional drag reduction, a technique by which bubbles are injected into the turbulent boundary layer surrounding the hull of a marine vessel, is now at the stage of practical applications. In achieving drag reduction, void waves often stand out naturally, the reason for which still remains unclear. The present study aims at an experimental characterization of void waves along a flat-bottom ship. A 100-m-long water reservoir is used in which a 4-m-long fully transparent experimental model ship, equipped with wall shear stress sensors and cameras, is towed by a train at speeds of up to 3 m/s. From measurements of the transition of the bubble distribution from random to wavy accumulated swarms downstream, the accompanying intrinsic passing frequency of void waves is examined. A 30% drag reduction rate was recorded with the appearance of void waves in the boundary layer at an average void fraction of 4%. This is much greater than the trivial inertia effect from drag reduction. To clarify the characteristics of the measured void waves, we compare the void wave frequency range to those of several flow instabilities that may occur in bubbly two-phase boundary layer flows. Graphical abstract: .
[en] This study examines the thermal behavior of a hemispherical electronic component subjected to a natural nanofluidic convective flow. During its operation, this active dome generates a high power, leading to Rayleigh number values reaching 4.56×109 . It is contained in a hemispherical enclosure and the space between the dome and the cupola is filled with a monophasic water-based copper nanofluid whose volume fraction varies between 0 (pure water) and 10%. According to the intended application, the disc of the enclosure may be tilted at an angle ranging from 0° to 180° (horizontal disc with dome facing upwards and downwards, respectively). The numerical solution has been obtained by means of the volume control method. The surface average temperature of the dome has been determined for many configurations obtained by combining the Rayleigh number, the cavity’s tilt angle and the nanofluid volume fraction which vary in wide ranges. The temperature fields presented for several configurations confirm the effects of natural convection. The results clearly highlight the effects of these influence parameters on the thermal state of the assembly. The study shows that some combinations of the Rayleigh-tilt angle-volume fraction are incompatible with a normal operating system at steady state and that a thermoregulation is required. The correlation of the temperature-Rayleigh-Prandtl-angle type proposed in this work allows to easily carry out the thermal dimensioning of the considered electronic assembly.