Applied Mechanics and Materials Vols. 592-594

Abstract: The effect of amino multi-walled carbon nanotubes (MWCNTs) on the flexural properties of epoxy/ nanocomposites was studied. Sonication technique was employed for dispersion of amino MWCNTs in epoxy. The properties of both neat epoxy and nanocomposites extensively studied by using three point bend test and scanning electron microscopy. From the experimental results, it was found that reinforcement with carbon nanotubes improved the flexural properties, namely (a) flexural modulus, (b) flexural strength, (c) nonlinear deformation and (d) total flexural toughness.

Abstract: Al-graphite and Al-Nanographite particulate metal matrix composites were prepared by two step stir casting method. The reinforced particulates in the metal matrix composites varied from 5% to 10% by volume fraction. Tribological performances of these composites were evaluated based on graphite particle size and normal load using a pin-on-disc tribometer. Al-Nanographite composites show higher load withstanding capacity and low coefficient of friction compared to aluminium graphite composites by the way of forming a thick graphite layer at the contact surface.

Abstract: Analysis of heat transfer behaviour of hybrid nanofluid (HyNF) flow through the tubular heat exchanger was experimentally investigated. In this analysis the effects of thermal characteristics of forced convection, Nusselt number, Peclet number, and overall heat transfer coefficient were investigated.The nanofluid was prepared by dispersing the copper-titania hybrid nanocomposite (HyNC) in the water. The experiments were performed for various nanoparticle volume concentrations addition in the base fluid from the range of 0.1% to 1.0%. The experimental results show that the overall heat transfer coefficient was found to increases maximum by 30.4%, up to 0.7% volume concentration of HyNC.

Abstract: The change in static and dynamic characteristics of polypropylene (PP) of grade H110MA by adding 2% multi walled carbon nanotubes (MWCNT) was investigated experimentally in this paper. The nanocomposite material is prepared by mixing neat PP and MWCNT in an extruder in a specified proportion. The extruded material is then used in an injection molding machine to make tensile test and impact test specimen. Tensile test specimen is tested on universal testing machine (UTM) to check the Young’s modulus of nanocomposite material. The impact test specimen is used to find the dynamic characteristics of this material by using the technique of experimental modal analysis using Single point Laser Doppler Vibrometer (SLDV), modal hammer and FFT analyzer. The scanning electron microscopic (SEM) images were taken to check the orientation and dispersion of carbon nanotubes in polypropylene.

Abstract: Nanofluid is nanomaterial suspended in base fluid. Nanoparticle enhances various properties of base fluid mainly heat transfer characteristics. Also sometime nanoblends means hybrid nanofluid is used. This article mainly states how nanofluids are formed from nanoparticle and there types. This paper reviews and summaries the recent work in experimental and theoretical heat transfer characteristic of nanofluid as well as nanoblends and it is helpful in identifying the nanofluid that can be used in heat pipe for further research.

Abstract: Micro sized particles such as SiC, Al₂O₃ and diamond particles reinforced with metal matrix composites are most commonly used in high performance applications like military, automotive and aerospace industries. Nowadays nano sized particles are replacing the micro sized particles because of their improved physical and mechanical properties. This paper reviews the stir processing method, mechanical properties, effect of particle size on properties of composites and structure of the metal matrix composites reinforced with nanoparticles. Among the variety of liquid metallurgy techniques processes available for preparing metal matrix composites, stir casting technique is generally accepted route and currently practised commercially because of its simplicity flexibility and Uniform distribution.

Abstract: Numerical investigations of Rayleigh-Bernard convection in enclosures of different modified bottom and top surfaces filled with Au-Water Nanofluid with different volume fractions are presented. This paper describes a numerical predication of heat transfer and fluid flow characteristics inside enclosures bounded by modified bottom and top surfaces and two periodic straight vertical walls. Simulations are carried out for a Rayleigh number of 6×10⁴ and two aspect ratios (0.25 & 0.5) with working fluid as Au-Water Nanofluid and The same analyses are performed with the Nanofluid having Au nanoparticles of same size and different volume fraction of φ = 5%, 10%, 15% and 20 % in order to see the effect of Nanofluid volume fraction on heat transfer. The Boussinesq approximation is used in order to take density change effect in the governing equations. The study investigates the effect of the nanoparticles volume fraction, and the aspect ratio on the heat transfer. The results are presented in terms of isotherms, streamlines local and average surface Nusselt numbers. Results show that the flow and isotherms are affected by the geometry shape and by the presence of nanoparticles with different volume fractions. It is also shown that for a fixed value of aspect ratio, the convective heat transfer is decreased for the increase in volume fraction of Nanofluid.

Abstract: Improving heat transfer characteristics in refrigeration and air conditioning systems has been intensively studied by many investigators. In the present work the effect of using CuO-R134a in the vapour compression system on the evaporating heat transfer coefficient is investigated by CFD heat transfer analysis using the FLUENT software. An experimental test rig is designed for this purpose. The test section is a horizontal tube in the tube heat exchanger made from copper. The refrigerant is evaporated inside an inner copper tube and the heat load is provided from hot water that passing in an annulus surrounding the inner tube. Heat transfer coefficients were evaluated using FLUENT for heat flux ranged from 10 to 40 kW/m², using nanoCuO concentrations ranged from 0.05 to 1% and particle size from 15 to 70 nm. The measurements indicated that for a certain nanoconcentration as heat flux or mass flux increases the evaporating heat transfer coefficient increases and also that the evaporating heat transfer coefficient increases with increasing nanoCuO concentrations up to certain value then decreases. The obtained evaporating heat transfer coefficient result have been optimized at its maximum value for the best CuOnano particles concentration in R134a refrigerant.

Abstract: This investigation is to understand the drilling characteristics of multi walled carbon nanotubes (MWCNTs) filled epoxy / glass fabric hybrid polymeric nanocomposite material, which will be influenced by the cutting parameters (Cutting speed and Feed rate) and various drill geometries. This test specimen was subjected to drilling tests with two drills of different tool geometries (HSS twist drill and HSS split point drill). Diameter of both drills was 7.14 mm. By measuring delamination at the entrance and exit sides of the drilled holes, as desired outputs, the drilling process is optimised using grey relational analysis. Based on grey relational grades, best and worst performances were noticed with HSS twist drill and HSS split point drill respectively. We also observed that the average of grey relational grades with HSS twist drill is slightly better than that of HSS split point drill.

Abstract: In the present work, Al-5083-5wt% nanoyttria powders were milled for 10, 20, 30 and 35 hrs in a high energy ball milling under optimised process parameters. The milled powders were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Milled powders exhibit nanocrystalline single phase after 10hrs of milling. Consolidation of 35 hrs milled powder was done by equal channel angular pressing (ECAP) through 90^o die channel angle using route A upto three passes with and without back pressure and sintered under controlled environment. Density of ECAPed samples was measured using Archimedes principle. The density is 96% for the sample consolidated with backpressure after two passes after sintering.