Assessment of flow induced vibration in a sodium-sodium heat exchanger

The 500 MWe Prototype Fast Breeder Reactor (PFBR) is under construction at Kalpakkam. It is a liquid metal sodium cooled pool type fast reactor with all primary components located inside a sodium pool. The heat produced due to fission in the core is transported by primary sodium to the secondary sodium in a sodium to sodium Intermediate Heat Exchanger (IHX), which in turn is transferred to water in the steam generator. PFBR IHX is a shell and tube type heat exchanger with primary sodium on shell side and secondary sodium in the tube side. Since IHX is one of the critical components placed inside the radioactive primary sodium, trouble-free operation of the IHX is very much essential for power plant availability. To validate the design and the adequacy of the support system provided for the IHX, flow induced vibration (FIV) experiments were carried out in a water test loop on a 60° sector model. This paper discusses the flow induced vibration measurements carried out in 60° sector model of IHX, the modeling criteria, the results and conclusion.     

Pressure drop and cavitation investigations on static helical-grooved square, triangular and curved cavity liquid labyrinth seals

Sodium cooled Fast Breeder Reactors (FBR) form the second stage of India's Nuclear power programme. Through a narrow annular space in the grid plate assembly of a prototype FBR, a very low leakage flow of liquid metal sodium should pass, experiencing a stipulated high pressure drop, and without much cavitation. To achieve this, a suitable labyrinth seal is required to be developed for use in the annulus. Water is employed as the model testing liquid which is estimated to experience a pressure drop ratio of 10.5 at the rated leakage flow. Previously studied circular or sinusoidal-grooved square, triangular or curved cavity labyrinth seals were unable to meet this value. In the present work, Computational Fluid Dynamics (CFD) analyses are carried out on Helical-grooved Square cavity Labyrinth Seals (HSLS), using commercial code Fluent. It is found that the geometrical configuration of the grooves plays a major role on the pressure drop. Experimental results reveal close agreement with CFD predictions. An optimal configuration of this square cavity seal is identified by applying genetic algorithm (GA) using commercial packages. It meets just about 24% of the targeted value. Later, using parametric CFD analyses, a Helical-grooved Triangular cavity Labyrinth Seal (HTLS) and different Helical-grooved Curved cavity Labyrinth Seals (HCLS) are analysed. The most favourable profile is tested and found to reach the required pressure drop. CFD cavitation analyses predict the intensity of cavitation in these seals to be below prohibitive levels.     

Texture, strain, and phase-fraction measurements during mechanical cycling in superelastic NiTi

Superelastic NiTi was subjected to simultaneous neutron diffraction and uniaxial compressive cycling between 10 and 980 MPa. The objective was an in-situ investigation of the evolution of the stress-induced, reversible transformation between austenite and martensite, to determine the cause of the changes in the macroscopic stress-strain response with cycling. Rietveld refinement was used to analyze the neutron spectra and quantify the phase fraction, texture, and elastic strain. The average phase strain in the mechanically loaded austenite (at a given stress) remained unaltered during the 100 load-unload cycles. However, differences in both the volume fraction and texture of austenite and martensite were noted as cycling progressed, suggesting that these factors are responsible for the changes in the macroscopic stress-strain response of NiTi with mechanical cycling.     

A Novel Narrow Band Red-Emitting Phosphor for White Light Emitting Diodes

Research on down conversion phosphor materials is the key for the development of solid-state lighting (SSL). Especially finding alternative red phosphor for white light emitting diodes (LEDs) based on blue or near ultraviolet (NUV) LEDs is important research task. In this view, we have synthesized a series of Eu³⁺-substituted La₂W_{2− x} Mo _x O₉ ( x =0–2, in step of 0.3) red phosphor and characterized by X-ray diffraction (XRD) and photoluminescence. XRD results reveal a phase transition from triclinic to cubic structure for x >0.2. All the compositions show broad charge transfer (CT) band due to CT from oxygen to tungsten/molybdenum and red emission due to Eu³⁺ ions. Select compositions show high red emission intensity compared with the commercial red phosphor under NUV/blue ray excitation. Hence, this candidate can be a possible red phosphor for white LEDs.     

Amino‐functionalised mesoporous silica microspheres for immobilisation of Candida antarctica lipase B – application towards greener production of 2,5‐furandicarboxylic acid

In the present study, amino‐functionalised mesoporous silica microspheres were utilised as support for the covalent immobilisation of Candida antarctica lipase B (CaLB) for the subsequent production of 2,5‐furandicarboxylic acid (FDCA) from 2,5‐diformylfuran (DFF). Under the optimised operating conditions of pH 6.5, particle/enzyme ratio of 1.25:1.0 and glutaraldehyde concentration of 4 mM, a maximum CaLB immobilisation yield of 82.4% on silica microspheres was obtained in 12.25 h. The immobilised CaLB was used for the synthesis of alkyl esters, which were utilised along with hydrogen peroxide for FDCA synthesis. The biocatalytic conversion of 30 mM DFF dictated a 77–79% FDCA in 48 h at 30°C; where the turnover number and turnover frequency of immobilised CaLB were 6220.73 mol mol⁻¹ and 129.59 h⁻¹, respectively, for ethyl acetate, against 6297.65 mol mol⁻¹ and 131.2 h⁻¹, respectively, for ethyl butyrate. Upon examining the operational stability, the immobilised CaLB exhibited high stability till five cycles of FDCA production.Inspec keywords: mesoporous materials, organic compounds, biotechnology, silicon compounds, renewable materials, catalysis, catalysts, enzymes, thermal stability, biofuelOther keywords: FDCA production, amino‐functionalised mesoporous silica microspheres, greener production, 2,5‐furandicarboxylic acid, covalent immobilisation, 2,5‐diformylfuran, CaLB immobilisation, Candida antarctica lipase B immobilisation, ethyl butyrate, time 48.0 hour, temperature 30.0 degC, time 12.25 hour     

Fundamentals of multidimensional multirate digital signal processing

This paper reviews the fundamentals of multidimensional multirate signal processing. Central to these discussions is the idea of generalized sampling-lattice. Topics discussed include nonrectangular decimators, interpolators, generalized DFT, and filter banks. The multidimensional polyphase decomposition is developed, with applications in decimation filtering and perfect reconstruction filter banks. Work supported in parts by National Science Foundation grants MIP 8919196, MIP 8604456, DCI 8552579, and matching funds from Hughes Aircraft Co., and Tektronix, Inc.     

Total sugar content in sorghum stalks and grains of selected cultivars from the world germplasm collection

Seventy sorghum cultivars from the world germplasm collection maintained at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) were screened for total sugar content of the stalks. The total sugar content in stalks harvested after physiological maturity ranged from 17.8 to 40.3% on dry weight basis. The total sugar content in grains of 15 selected cultivars ranged from 1.02 to 2.23%. Nine cultivars having more than 34% total sugar content in stalks showed consistency for sugar content when grown for two seasons. Juiciness of stalks from five cultivars as estimated by the quantity of juice extracted varied from 266 to 464 ml per kilogram of fresh stalks. The total sugar content in the juice of five cultivars varied from 7.0 to 15.9%.     

Characterisation of Microstructures,Deformation, and Fatigue Damage in Different Steels Using Magnetic Barkhausen Emission Technique

The characterization of microstructures, mechanical properties, deformation, damage initiation, and growth by Non-Destructive Evaluation (NDE) techniques is assuming a vital role in various industries because of the growing awareness of the benefits that can be derived by using NDE techniques for assessing the performance of various components. NDE is widely applied for assessment of material degradation, where investment in new plants is not cost-effective and safe operational life of existing plants needs to be extended. In recent years, various advanced NDE techniques have been successfully employed for characterization of defects and microstructural features such as grain size, texture, nucleation and growth of second phases, assessment of tensile, creep and fatigue properties, deformation, and damage. With the advent of fracture mechanics concepts, microstructure, defects as well as stresses must be quantitatively characterized to have reliable and fail-safe materials and components. Any alteration in the microstructure, which reduces the life or performance, should be predicted sufficiently in advance in order to ensure safe, reliable, and economic operation of the components. This is possible when one realizes that the interaction of the nondestructive probing medium with the material depends on the substructural/microstructural features such as point defects, dislocations, voids, micro and macro cracks, secondary phases, texture, residual stress, etc. In this paper, use of Magnetic Barkhausen Emission technique for characterization of microstructures, deformation, and fatigue damage in different steels would be discussed. When a ferromagnetic material is subjected to a varying magnetic field, the magnetic flux densidy during magnetization varies in discrete steps as the magnetic domain walls have to overcome various types of obstacles during their movement. The discrete changes in magnetization induce electric voltage pulses in pickup coil placed near the surface of ferromagnetic materials. This noise like voltage pulses were, firstly observed by Barkhausen in 1919 and this phenomenon is named as magnetic Barkhausen Noise (MBN) or magnetic Barkhausen emission (MBE). Based on the two stage magnetization process modeled by the authors, the size of the grain/lath and carbides in ferritic steels could be correlated with MBE parameters. The influence of morphology of cementite (lamellar and spheroidized) on the MBE behaviour has been understood. Various stages of tensile deformation, viz. (i) perfectly elastic, (ii) micro-plastic yielding, (iii) macroyielding, and (iv) progressive plastic deformation in ferritic steels could be identified using the MBE parameters. The hardening depth and its quality with respect to the microstructure in induction hardened specimens could also be established using the MBE technique. MBE is found to be highly sensitive in detection of stress induced martensite in stainless steels with metastable austenite phase. Different stages of fatigue damage in 9Cr-1Mo steel, viz. (i) cyclic hardening, (ii) softening, (iii) saturation, and (iv) crack initiation could be identified using the MBE parameters.