Experimental and thermal analysis of energy efficient novel design wet cooling towers

Waste heat is generally dissipated from process water to atmospheric air in cooling towers. In the present study, a novel design is used to extract more amount of heat without any additional energy input by incorporating secondary ambient air in an induced draft wet cooling tower. In addition, more fresh air is induced in the tower from the rain zone, which increases the effectiveness at any value of the water to air flow rate (L/G ratio). Moreover, tower characteristics, range, and evaporation loss were also increased due to the novel design. It is noteworthy that secondary fresh air increases effectiveness, heat rejection, and tower characteristics by 10.12%, 19.65%, and 26.11%, respectively, and decreases approach by 16.32% at 0.55 L/G ratio, 44°C inlet water temperature, 29.7°C dry bulb temperature, and 18.4°C inlet air wet bulb temperature.     

FULLY DEVELOPED LAMINAR HEAT TRANSFER IN CIRCULAR-SEGMENT DUCTS WITH UNIFORM WALL TEMPERATURE

Heat transfer to constant-property, fully developed, laminar flows in circular-segment ducts with uniform wall temperature (T) has been analyzed. Besides representing a compact surface, the segment duct geometry models the flow cross section of a circular tube with a straight-tape insert. Two variations in the T thermal boundary condition are considered: constant axial and circumferential wall temperature, and constant temperature on the curved surface but an adiabatic flat wall. These two conditions model the extremes of the fin effects of a straight-tape insert, i.e., 100% and zero fin efficiencies, respectively. Numerical solutions, obtained by using finite difference techniques, are presented for both the velocity and temperature fields. The isothermal friction factors are in excellent agreement with analytical solutions reported in the literature. The Nusselt number results for the two thermal boundary conditions are presented for different segment shapes, 0° ≤, 6 ≤, 90°, and they represent the lower limits of the heat transfer enhancement due to twisted-tape inserts.     

Double dispersed bioconvective Casson nanofluid fluid flow over a nonlinear convective stretching sheet in suspension of gyrotactic microorganism

Microorganisms play a vital role in understanding the ecological system. The motions of micororganisms are self‐propelled while the impact of thermophoresis and Brownian motion property of nanoparticle shows more challenges in biotechnological and medical applications. The present problem is based on the understanding of double‐dispensed bioconvection for a Casson nanofluid flow over a stretching sheet. Suction phenomenon is introduced at the surface of the stretching sheet along with the convective boundary condition. The convection and movement of the microorganisms are assisted by an applied magnetic field, nonlinear thermal radiation, and first‐order chemical reaction. The governing equations are highly coupled and thus we used the spectral quasilinearization method to solve the governing equations. The study of the residual errors on the systemic parameters had given a confidence with the present results. The final outcomes are displayed through graphs and tables. The thermal dispersion coefficient shows a positive response in the temperature while a similar response is observed for the concentration with solutal dispersion coefficient. The response is reversible for the heat transfer rate at the surface with thermal dispersion coefficient. The density of the motile microorganism at the surface decreases with increase in the Casson number, thermal dispersion coefficient, and solute dispersion coefficient, while an opposite phenomenon was observed with increase in the density ratio of the motile microorganism.     

Facile synthesis of rice shaped CuO nanostructures for battery application

The oxides of transition metals are an important class of semiconductors, which have applications in electronics, magnetic storage media, solar applications and catalysis. Among them, CuO has attracted much attention due to its widespread applications. In this paper, a facile synthesis of rice shaped CuO nanostructures have been prepared by reflux method for battery application using Copper nitrate and ammonia as precursors. Samples were prepared at three different reaction timings namely 6, 12 and 24 h. The as-prepared samples were calcinated at 400 °C to ensure the formation of copper oxide. The final products were subjected to X-ray diffraction, scanning electron microscopy, FT-IR and UV–Vis spectroscopy in order to study the effect of reaction time on the properties of the prepared copper oxide nanostructures. It is found that at controlled reaction time rice shaped CuO nanostructures are obtained. Cyclic voltammogram was recorded to understand the electrocatalytic behaviors of the rice shaped CuO sample prepared under optimized condition.     

Phenomena of reverse momentum pulse and fluid leak after poison injection in the shut down system of PHWR

The primary function of the shut down system in a nuclear reactor is to terminate any reactivity transient occurring in the core during its entire design life. Normally there is more than one system, which are independent and diverse in its mode of operation. They consist of quick acting mechanisms like dropping of safety rods by gravity, poison injection, etc. Typically in liquid poison injection system wherein high flow velocities are involved, there is significant fluid structure interaction associated with cyclic shock transients in the system. One such phenomenon has been captured and analyzed to understand the dynamics involved in the loop. The trends of loop pressure and vibration indicated presence of more than two pressure transients after complete injection of poison. The first transient arrived after 1.44 s and the second after 0.75 s. The reverse pressure pulses that manifested in the loop as a result of fast injection of fluid has been mathematically characterized by solving basic fluid balance equations. Possibility of ball lifting due to momentum pulse is also discussed.     

Sizing Cracks in Power Plant Components Using Array Based Ultrasonic Techniques

New techniques developed using the array transducer, to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components are discussed. Three studies are reported here including (a) Optimal beam steering angle for focused and unfocused inspection using phased array method for bottom-surface crack sizing. (b) A front wall correction algorithm for sizing of near-through-wall crack-like defects. (c) A small aperture technique for sizing of near-through-wall crack-like defects. A Finite Difference Time Domain (FDTD) based simulation was used to study and verify the experimental observations. The application of time domain scheme relative arrival time technique (RATT), to measure the size of the near-through wall crack-like defects for the leak before break (LBB) criterion, was also investigated and found to be insufficient. A conventional SAFT algorithm was used for improving the sizing using the small aperture technique.     

A Novel In Situ Method for Producing a Dispersion of a Ceramic Phase into Copper That Remains Stable at 0.9T M

We apply an in situ approach, whereby a polymer is incorporated into copper and evolves within the metal into the ceramic phase, to create a dispersion of hard particles in a metal. All constituents for the ceramic phase are contained within the organic polymer. The temperature for this polymer to ceramic conversion lies in the 1073 K to 1273 K (800 °C to 1000 °C) range. The process produces a nanoscale dispersion of the ceramic, which leads to high microhardness that remains unaltered at temperatures up to 1223 K (950 °C) (0.9T _M). Apparently, the introduction of the ceramic phase leads to the retention of copper crystallite size of a few hundred nm, despite exposure to heat treatments at these very high temperatures. We call these materials polymer-derived metal-matrix composites.     

Effect of Microstructural Parameters on the Relative Densities of Metal Foams

A detailed quantitative microstructural analyses of primarily open cell FeCrAlY and 314 stainless steel metal foams with different relative densities and pores per inch (p.p.i.) were undertaken in the present investigation to determine the effect of microstructural parameters on the relative densities of metal foams. Several elements of the microstructure, such as major and minor cell sizes, cell areas and perimeters, ligament dimensions, cell shapes, and area fractions of closed and open cells, were measured. The cross-sections of the foam ligaments showed numerous pores, and their circularity factors and average sizes were determined. The area fractions of the open cells and ligaments decreased, whereas that of the closed cells increased linearly with increasing relative density. The relative densities and p.p.i. were not significantly dependent on cell size, cell perimeter, and ligament dimensions within the limits of experimental scatter. A phenomenological model is proposed to rationalize the present microstructural observations.     

Characterisation of solution annealed VT-14 titanium alloy using eddy current based electrical resistivity measurements

This paper discusses characterisation of microstructures in Ti-4.5Al-3Mo-1V (VT-14) alloy specimens solutionized in the temperature range of 923K–1373K, using room temperature electrical resistivity measurements. Using phase angle of impedance change in eddy current coil as a parameter, calibration curve between resistivity and phase angle has been established using three reference specimens of known resistivity. The changes in the electrical resistivity of the specimens have been correlated with optical microscopy investigations. The electrical resistivity of unstable β phase has been compared with α and α′ phases and possible reasons for higher resistivity of β phase and lower resistivity of α′ have been given based on the rule of mixtures and scattering and mobility of electrons. The electrical resistivity of α′ martensite phase of the chosen VT-14 alloy has been determined as 1.04 αΩ-m. The studies reveal that it may be possible to identify the β transus temperature of α+β titanium alloys from the electrical resistivity data.