Journal of Modern Thermodynamics in Mechanical System (e-ISSN: 2582-5771)

Grain Refinement of Al-Si Alloys: Scientific and Industrial Aspects

Sachin Kumar Rathi — 2019-02-15

Casting of aluminum alloys is a common industrial practice and widely used in automotive industry in the entire world. This practice is used to promote the formation of a fine, uniform and equiaxed grain structure. To understand the mechanism of grain refinement is very important since a refined microstructure lead to improve uniform mechanical properties and reduced hot tearing tendency of the alloy by improving feeding ability of liquid metal. Sufficient amount of liquid fraction at last stage of solidification ensure the less shrinkage porosity, and finer distribution of second phases. Nowadays in casting industry, finer grain structure is achieved by addition of grain refiner in the melt. The most commonly used inoculants are Al-Ti, Al–Ti–B, and Al-Ti-C master alloys. Usually Al–5Ti–1B is added to molten aluminum at a typical level of .01 to .05 by weight of titanium. After addition of grain refiner, the number of active nucleation sites during solidification start to dispersed in the melt and nucleate solid particles. There are two mechanism of grain refinement; (i) Nucleant effect: it promotes suitable sites for heterogeneous nucleation of grains, and (ii) Solute effect: it restricts the growth of grains through segregation of solute elements. It has been seen that TiAl3 and TiB2 particles are the maximum common heterogeneous nucleation particles for aluminium crystals. The required driving force for grain refinement during solidification is provided by cooling rates in the form of constitutional undercooling. Many researcher has given a great contribute to understand the mechanism of grain refinement in melt. However, the exact mechanisms by which grain refinement occurs using the grain refiner have not been fully understood yet. Experimental and theoretical studies on the mechanisms have mainly focused on (a) the role of the titanium solute causing a growth restriction effect, (b) the thermodynamics of Al–Ti-based alloy systems, and (c) the heterogeneous nuclei of TiAl3 and TiB2 particles. In the present paper, a review is given of the studies of grain refinement taking into consideration of both the industrial practice and scientific aspects of grain refinement. The paper will be useful in understanding the performance of grain refiners for the scientific and industrial community.

Analytical Modeling of Energy and Efficiency of Cryogenic Energy Storage Plant Using Various Working Fluids to Identify Best One for Load Shifting of Nuclear Power Plant and Renewable Energy Sources

A. Kanni Raj — 2019-04-14

Cryogenic energy storage (CES) systems are good electricity storage method. In CES systems, excess current is used to liquefy gas. Liquid (cryogen) can be stored in large cryogenic tanks for a long time. Whenever there is demand for electric current, cryogen is warmed by waste heat to obtain gas. Gas so generated is then used to run gas turbine and generate electric current. Most researches are on air-based CES, as air is easily available. CES with other working fluids exhibit higher efficiency. In current modeling work, performance analysis of CES systems was done for different types of cryogens. Finally, it is concluded that CES with methane (natural gas) as the working fluid could exhibit highest efficiency.

Latest Trends in Novel Applications of Various Heat Exchangers for Enhancement of Heat Transfer

Bhavik J. Pandya — 2019-03-13

A heat exchanger is equipment used for transfer of heat from one medium to other medium. Heat exchangers are fundamental parts in many process industries (such as power plants or the chemical and the food industries), and as heat recovery units in the operation of many systems (such as domestic hot water production, space heating or car engines).In a compact structure of cryogenic and other industrial applications for enhancement of heat transfer, coil heat exchangers are generally used. Currently, increase in efficiency of heat exchanger and heat transfer rate of heat exchanger, lots of researchers are working on it.

Study of Crack Propagation of Brake Disc Using Furnace

B.N.Ghodake — 2019-01-12

Because of severe operational conditions, many working components are subjected to complex combination of cyclic temperature & mechanical loading. Premature failure is the major problem encountered in the operation of brake discs. To determine the nature of cracks the failure investigation described in this study was carried out by using different experimental methods as Fatigue tester method, NDT, Bentch study braking equipment, Furnace experimental testing, Chemical Testing etc. In the furnace experimental testing stainless steel specimen with a pre-existing surface notch is exposed to a convective medium of cyclic temperature. In Batch study, braking equipment wheel-mounted forged steel brake discs are exposed to heavy thermal and mechanical loadings and subjected to high thermal shock loading during routine braking and emergency braking. The present study was carried to develop simple method for studying the crack propagation with the aim of developing brake discs with increased lifespan, so as to improve the safety and reliability of these components.

Numerical Study of Heat Transfer through Fin by using ANSYS-Fluent Model

Basima S. Khalaf — 2019-03-28

A mathematical model of the process occurring on fin at same height and different height with different heat flux (10000, 20000, 30000 w/m2) have been investigated. The model is developed using principles of heat transfer, fluid dynamics, and these values used for comparing with two height of fin which used in electronically device like computer. The distributions of velocity and temperature was found along flow path of fin cell using the software computer (ANSYS FLUENT 16.1), this software was developed to apply the theoretical model to simple three -dimensional geometry. Finally the optimal heat flux and temperature along fin has been obtained for five tests of fins, and a good agreement is found between theoretical results with previous works.