Papers by Keyword: Phase Change

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Authors: Musfiroh Jani, Mark E. Hodson, Ann M. Chippindale
Abstract: This study presents the experiments on the in-situ powder XRD on pure hydrous ferrous sulfate (FeSO4.nH2O) mineral. The progress of this mineral was monitored at different relative humidities and temperatures. The phase transformation from melanterite (FeSO4.7H2O) to rozenite (FeSO4.4H2O) and the phase transformation of rozenite (FeSO4.4H2O) to szomolnokite (FeSO4.H2O) were obtained.
257
Authors: Gelu Coman, Cristian Iosifescu, Valeriu Damian
Abstract: The paper presents the experimental and theoretical study for temperature distribution around the cooling pipes of an ice rink pad. The heat transfer in the skating rink track is nonstationary and phase changing. In case of skating rinks equipped with pipe registers, the temperature field during the ice formation process can’t be modeled by analytical methods. The experimental research was targeted on finding the temperatures in several points of the pad and also details on ice shape and quality around the pipes. The temperatures measured on the skating ring surface using thermocouples is impossible due to the larger diameter of the thermocouple bulb compared with the air-water surfaces thickness. For this reason we used to measure the temperature by thermography method, thus reducing the errors The experimental results were compared against the numerical modeling using finite elements.
353
Authors: I.M. Fielden, J.M. Rodenburg
Abstract: We present a novel electron detector and technique permitting orientation contrast images to be generated using back-scattered electron signals. The detector is a modification of the converter plate. It is unaffected by Infra-Red and light photons and invulnerable to the effects of heat. Consequently, the detector is removed as the temperature limiting factor in elevated temperature SEM grain observations. The detector has been successfully applied to an environmental SEM (ESEM) operating in high vacuum mode and has produced good quality video image sequences of hot metal specimens with frame rates between 1 per second and 1 per 30 seconds (largely material dependent). Temperatures attained were up to 850°C, limited by the capability of the hot stage. Although developed for the ESEM the technique is applicable to any SEM provided that adequate measures are taken to manage contamination and heat effects on other microscope components. We have produced images and short, accelerated video sequences of recrystallisation and grain growth phenomena in steel, aluminium, copper and gold by the new technique. The technique has also successfully imaged phase transformations and high temperature behaviour of microelectronic materials.
1385
Authors: Jun Inoue, Tadachika Nakayama, Tsuneo Suzuki, Hisayuki Suematsu, Wei Hua Jiang, Koichi Niihara
Abstract: Chromium oxynitride (Cr(N,O)) thin film have been successfully prepared by using pulsed laser deposition. The composition of the thin film was determined to be Cr0.50N0.23O0.28 by Ruthreford backscattering spectroscopy (RBS). The structural analysis was carried out by using X-ray diffraction (XRD), and out-of-plane and in-plane measurements were used to clarify the axial ratio (c/a) of the Cr(N,O) phase. The lattice constants of a and c axes in the Cr(N,O) phase were found to be 0.414 and 0.419 nm, respectively. From these results, the cubic to tetragonal phase change by substitution of the oxygen atoms for nitrogen atoms was confirmed for the crystal Cr(N,O) compounds.
1006
Authors: Ryoichi Chiba
Abstract: The two-dimensional differential transform method is applied to solve the one-dimensional phase change problem for a solid sphere with time-dependent boundary temperature. The problem assumes that the phase change occurs over a range of temperatures and the initial temperature of the sphere is an arbitrary constant. An approximate analytical (series) solution is derived for the temperature profile in the melting or solidifying sphere. The solution is based on the apparent specific heat method. Numerical results illustrate the effects of the Stefan number, which is the ratio of sensible heat to latent heat, on the transient temperature profile in the sphere.
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Authors: Su Shia Lin
Abstract: The Bi-Ge-Sb-Te phase-change recording films were prepared by DC magnetron sputtering of Bi5Ge9Sb68Te18 and Bi5Ge3Sb74Te18 targets, individually. The surface roughness of Bi5Ge9Sb68Te18 film was relatively low. At the recording speed of 27.92 m/s, the jitter value of Bi5Ge9Sb68Te18 disk was 21.33%, but Bi5Ge3Sb74Te18 disk could not be recorded. After the aging test, the reflectivity change (Rbef.−Raft.) of Bi5Ge9Sb68Te18 film was obviously less. It could be found that the Bi5Ge9Sb68Te18 film was suitable for high-speed recording and showed the better archival life stability. As the results, the recording performance and archival life stability of phase-change optical disks were dominated by the composition of recording film.
293
Authors: Rakesh Hari, Tom Jolly, C. Muraleedharan
Abstract: The two-phase flow through porous media is an important topic which spans a broad spectrum of engineering disciplines especially in porous heat pipes. Heat pipe is a thermodynamic device that transports heat energy from one location to another with a negligible temperature drop. The aim of the present work is to investigate the phase change mechanisms, namely boiling and condensation, in the flat heat pipe system with different orientation. Governing equations used for the formulation are continuity, mixture momentum, liquid conservation and energy equations. These equations are converted into three ordinary differential equations using similarity transformation and two-phase similarity solutions are obtained for both boiling and condensing flows. In each case, a two phase zone where the liquid and vapour can coexist appears adjacent to the wall. As the heat transfer at the wall gradually enhances, the liquid saturation at the wall approaches to the limiting value, zero, for boiling and unity for condensation. The present work is an attempt to predict numerically the liquid wall saturation, non-dimensional temperature, non-dimensional temperature gradient and effect of Sherwood number during the phase change of water-steam system in the heat pipe for horizontal and vertical cases. Nomenclature
1461
Authors: S. Arulanantha Samy, T. Shanmuganathan, J. Godwin John
Abstract: The recent vehicle management systems have been developing to improve the quality of the combustion process and transmission systems. In thermodynamic approach, the water molecule can exists in different phases like ice, water, wet steam, dry steam, and superheated steam. The phase change occurs in the steam formation process can be compared to the various stages of any vehicle dynamic system such starting, idling, normal speed, high speed and very high speed. There may be an identical value in the increment of energy level in both steam formation process and any vehicle dynamic system. Thermodynamic approach always deals with system, surroundings, boundary and energy transformation across boundaries. Entropy is a very good property which is used to find the energy degradation in a particular system, and this property existence in the vehicle dynamics of automobiles will be used to improve the efficiency of the control module of a vehicle management system. This paper initiates a new angle research in the field of vehicle dynamics to study and investigate the kinetic energy transformation and distance moved by the vehicle thermodynamically. From this paper, Entropy is found as a very good property for increasing the mileage of the vehicle. In the vehicle health monitoring, there should be an entropy measurement to reduce the unavailability of energy as it is the measure of the distance travelled by the vehicle per unit energy supplied to the same vehicle at various operating speeds. In manual transmission method, it has been found that driver is not able to press the accelerator pedal continuously due to body strain. Driver has to run the vehicle at constant speed by pressing the accelerator pedal continuously. In automatic transmission, the data required for the ECU module is given by the thermodynamic relations such as enthalpy, entropy and internal energy. This paper aims thermodynamically to describe the speed, acceleration, fuel consumption, kinetic energy and various resistances offered to the vehicles. Generally, Thermodynamic system deals with heat and mass transfer, likewise vehicle dynamics deals with work and vehicle’s motion.
118
Authors: Rahul Basu
Abstract: This paper examines a model for coupled heat and mass transfer for freezing in a porous matrix with Dirichlet and convective boundary conditions. Variables include porosity, heat transfer coefficients, thermal and mass diffusivity, density, latent heat and boundary temperatures. It is shown that heat and mass transfer balance at the interface can affect stability. The effect of boundary conditions on the velocity of freezing is computed for some cases, and applications to physical problems highlighted
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Authors: M. Nurullah Turgut, M. Hakan Demir, Faruk Yigit
Abstract: The mold-shell interface plays a very important role during the earliest stages of metal casting processes. Heat is extracted from the molten metal through this interface resulting in the growth of the shell. Small spatial variations in heat extraction can lead to shell morphological instability where certain regions of the solidification front grow preferentially over others. This may cause cracks in the shell which can greatly reduce the integrity of the final cast product. Mold coating at the mold-shell interface is one of the most important factors controlling the heat transfer and, hence, it has very important role on the solidification rate and development of microstructure. In this paper, a linear perturbation method is used to solve a two-dimensional heat conduction problem in which a liquid, becomes solidified by heat transfer to a planar mold of finite thickness. The influence of physical parameters such as the coating material thickness, conductivity and thermal contact resistance on the growth of solidified shell thickness is investigated. The present work can form the thermal part of a subsequent investigation of related thermo elastic stress problems.
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