Applied Mechanics and Materials Vols. 465-466

Abstract: The vertical single-phase flow was studied on the shell side of a horizontal tube bundle. In the present study, CFX version 14.0 from ANSYS was used to predict the flow regimes in the two tube bundles; i.e. the 19 mm and 38 mm arranged in an in-line configuration with a pitch to diameter ratio of 1.32. The simulations were undertaken to inform on how the fluid flowed within the tube passages in different tube bundle diameter that gives different gaps between the tubes, where the fluid must pass. The results show that the maximum gaps between the tubes have no clear effect to the flow where the flow separation and re-attachment and the average velocity is the same when increasing the tube bundle. This is consistent with other published data.

Abstract: This paper present a two-phase pressure drop model for a in-line tube bundle for airwater mixtures flowing through an idealised shell and tube, in-line heat exchanger. The model used momentum flux and entrained liquid fraction to predict the acceleration pressure drop. The model predicts the pressure drop well using both accelaration and gravitational pressure drop deduced from data available in open literature. The model is shown to be mass flux dependence.

Abstract: This study evaluates five turbulence models to determine the best models to be implemented as it representing the turbulent flow inside the lab scale classifier. The models studied are: The standard ƙ-ɛ model, Renormalization-group (RNG) ƙ-ɛ model, Realizable ƙ-ɛ model, Standard k-ω model, and Reynolds stress model (RSM). Through analysis of air flow, the air velocity data can be obtained from computational fluid dynamics (CFD), the result shows that, standard ƙ-ɛ model and Realizable ƙ-ɛ model are found to be more appropriate to use than the other turbulence models. The model validation is conducted by comparing the simulated velocities with experimental data in a lab scale classifier from literature. ANSYS software is selected to be used to run the simulation and analysis.

Abstract: Experimental works were conducted to investigate the effect of Al2O3 sizes and volumeconcentration on the rate of nanofluids heat transfer in a compact heat exchanger. Two sizes ofAl2O3 nanoparticle, 40 nm and 100 nm, were mixed with demineralized water at 2% and 10%volume concentrations. Sodium Lauryl Sulphate (SLS) powder was added to enhance the mixingprocess and stabilize the dispersion of the nanofluids. A custom-made closed loop test rig weredesigned, fabricated and tested for these experiments. The test rig was set-up to represent the actualapplication of the nanofluids in cooling of a compact heat exchanger. Experimental runs wereconducted which include the runs for water, 40 nm Al2O3-water and 100 nm Al2O3-water. Theresults indicate that Al2O3-water gave better heat transfer performance than water alone. Nanofluidswith 40 nm- Al2O3 gives better heat transfer performance as compared to 100 nm- Al2O3 nanofluids.The results of the current work generally indicate that nanofluids have the potential to enhance theheat transfer of a compact heat exchanger if properly designed. This superior performance of thenanofluids would only be produced if smaller diameter of nanoparticles were used (less than 100nm). No enhancement in heat transfer can be observed by using nanofluids with particle size of 100nm or at higher volume loading (more than 5%).

Abstract: The presented paper deals with the influence of manufacturing process on the stress state of mechanical parts. The problem is presented in the assembly of the belt drum. The connections of individual parts are realized by press fitting and welding technology. The practical use of the belt drum shows the initiation of cracks in the weld body. The presence of press fitting connection in the structure is marked as the origin of high stresses in the weld body. The paper proposes the new assembly method in order to reduce the stress level in the weld structure and points the assembly method as one of important factors influencing the stress state of mechanical parts.

Abstract: This paper investigates and presents the simulation of drying for hygroscopic and nonhygroscopic materials. This present work used a coupled mathematical model of mass, heat and gas transfer that implemented to finite element method in two dimensional and numerically compute using Skyline solver to capture highly nonlinear transient process. Bound water contribution was taken into account in the drying of hygroscopic materials by incorporating constitutive equation of bound water. The results showed drying process can be divided into three periods named constant rate period (CRP), first falling rate period (FRP1) and second falling rate period (FRP2). Capillary action is dominated during CRP before vapour diffusion takes place in FRP1. Bound water movement is generated by vapour pressure gradient exists that represent hygroscopic material.

Abstract: The high speed machining (HSM) of gray cast iron for manufacture mold and dies involve many different cutting tool from deep hole drills to smallest ball nose end mills [. Due to the demand of fast and high productivity, high speed machining (HSM) has been increasingly used to produce mold and dies that are mostly used in automotive industry especially for stamping dies components. The process of HSM sometimes combined together with manual polishing to enhance the die surface into fine mirror finish. Although the manual polishing strongly depends by experience and skill of workers, this technique is the preferable option for polishing of moulds and dies. However, such extensive manual polishing will provide some drawback because of many human factors such as pressure and technique of polishing individual person uses. Therefore, the application high speed machining in manufacturing is still demanding as it can improve surface finishing by reducing manual polishing, reportedly account for up to 30% of the total time [2].

Abstract: In this paper, mechanical properties of Al functionally graded materials (FGMs) crash box fabricated by heat treatment is predicted based on temperature distribution and experimental data. The Al FGM crash box is fabricated by applying different temperature at the both ends of a square hollow Al column for 4 hours. Due to the gradient in heat treatment temperature along the height of the Al column, the microstructure is locally varied so that a certain variation of local material properties is achieved. The determination of material properties at any point along the height of Al FGM crash box experimentally is uneasy. The Lagrange interpolation method is proposed to predict the variation of local material properties at any point along the height of Al FGM crash box for further work such as simulation of impact on the crash box. The determination of mechanical properties is successfully predicted using the available experimental data and the temperature distribution obtained in simulation.

Abstract: Noise-Induced Hearing Loss (NIHL) has become a major health threat to the Malaysian industrial workers in the recent era due to exposure to high frequency noise produced by the heavy machines. Recently, many studies have been conducted to diagnose the NIHL in industrial workers but unfortunately they neglected some factors that can play a major role in speeding-up NIHL. In this paper, a new Hybrid Bat-BP algorithm which is based on the trio combination of BAT based metaheuristic optimization, back-propagation neural network, and fuzzy logic is proposed to diagnose NIHL in Malaysian industrial workers. The proposed Hybrid Bat-BP will use heat, body mass index (BMI), diabetes, and smoking along with the century old audiometric variables (i.e. age, frequency, and duration of exposure) to better predict NIHL in Malaysian workers. The results obtained through Hybrid Bat-BP will be able to help us identify and reduce the NIHL rate in the workers with high accuracy.

Abstract: Solidification of metals continues to be a phenomenon of great interest to physicists, metallurgists, casting engineers and software developers. It is a non-linear transient phenomenon, posing a challenge in terms of modelling and analysis. This paper attempts to study heat flow within the casting, as well as from the casting to the mould, and finally obtains the temperature history of all points inside the casting. The most important instant of time is when the hottest region inside the casting is solidifying. ANSYS software has been used to obtain the last solidifying region in the casting process by performing transient thermal analysis. Location of the hot spot predicted by software simulation showed good agreement with the experimental trial. It was also observed that the simulation of casting helps in obtaining optimum design of riser.