Papers by Keyword: Cooling

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Authors: R.W.L. Fong, H. Saari, R. Miller, J. Teutsch, Sven C. Vogel
Abstract: Differential scanning calorimetry (DSC) has been used to study the phase changes in samples of as-received Zr-2.5Nb pressure tube material by continuous heating and cooling. Two different heating rates (5 and 20°C/min) were used to heat the sample up to 1050°C. After a short time hold at 1050°C, all the samples were continuously cooled to 300°C at a rate of 20°C/min. On continuous heating, the DSC signals obtained showed two endothermic transitions. The low-temperature transition, occurring between about 500 and 650°C, is attributed to a thermal decomposition of metastable niobium-stabilized β-phase. The highertemperature transition, occurring between 600 and 950°C, is due to phase transformations of hcp α-Zr to bcc β-Zr, as previously confirmed in a companion study on the same pressure-tube material that was examined in-situ by neutron diffraction. The neutron diffraction results provided a positive identification of the two phases and also a quantification of the β-phase present in the sample at different heating temperatures, and thus provided a guide to extract the volume fraction of β-phase from the DSC signals obtained in this study. The DSC signals revealed only one exothermic transition which is correlated to the reverse transformation of β-Zr to α-Zr, as previously identified in the companion neutron diffraction study of the same pressure tube material.
Authors: De Feng Zhang, Yin Liang, Zhong Lin Du, Xiao Huang Mao
Abstract: The time-dependent inhomogeneous temperature distribution in steel plates during the cooling increases thermal strains which, in turn, generate plastification and thus residual stresses. Moreover, phase transformation from the parent austenite phases into a product phase typically entails not only metallurgical strains but also accounts for transformation induced plasticity (TRIP), which again generates transformation related residual stresses. A unified material model that consisting of all relevant contributions to the total strain rate, i.e., elastic, plastic, thermal, metallurgical and TRIP strain contributions could be built in this paper. Transformation also released a significant amount of latent heat which naturally affected the temperature field that governed the evolution of the product phase. For the latter kinetic relationship about difference between diffusive and displacive transformation mechanisms depending on the local cooling rate is presented. Using an Avrami-like approach, the transformation kinetics is set up especially for complex cooling histories. The material model simulated the evolution of the residual stresses as well as the warping of the steel plates after completely cooling to room temperature.
Authors: Agus Sunjarianto Pamitran, Helmi Dadang Ardiansyah, Mach Novviali
Abstract: Sea-water ice slurry generator is aimed to produce ice-slurry using sea-water while fishing on boat. Some models of ice slurry generator have been researched and developed. Indonesia as an archipelago and maritime nation has big potential in fishery. Appropriate model for Indonesian traditional fishing boat is necessary. The most important part of ice slurry generator is evaporator, including auger and scrapper. Some studies on ice slurry are presented in this review paper in order to get larger view on design of ice slurry generator.
Authors: Zi Qin Ma, Yan An Chen, Peng Fei Zhao, Tong Wang, Chen Peng, Li Sun, Qiang Cheng, Jiang Wei
Abstract: High-speed cutting technology has become an important development direction of modern NC machining technology, but the existing equipments are often not suitable for high speed machining. An effective method is proposed in view of the cutting heat in cutting process, by introducing chiller to the existing cooling system, the coolant temperature decrease, tool and workpiece temperature can also reduce, so general machining center can achieve cutting speed as quickly as possible.
Authors: Radim Uhlář, Libor M. Hlaváč, Lucie Gembalova, Petr Jonšta, Ondřej Zuchnický
Abstract: The paper is aimed at abrasive water jetting of non-corroding steels treated by cryogenic temperatures in liquid nitrogen. The investigation of cut walls shows that cryogenic temperatures influence material structure and respective properties. This research is focused on improvement of material reliability in various states of production systems and operation conditions.
Authors: Bernd Arno Behrens, Tobias Prüß
Abstract: The temperature of forging dies has a high influence on the wear development of the tool surface. To reduce the thermal impact on tool life cooling lubricants are used in many manufacturing processes. They perform two functions: tool cooling and reduction of friction. Cooling lubricants must always meet these two requirements. Within this article the separation and the particular optimization of both functions is presented.As an alternative to a graphite-water-mixture, boron nitride is the medium of choice for lubrication purposes, since it features excellent lubricant properties. For a high wettability it is applied by electrostatic coating.As an alternative approach to removing heat from a forging die, the usage of heat pipes is for the first time investigated in this paper. These passive elements are able to transport heat without using external energy. They will be varied in form and volume. This cooling method will be qualified for the use in forging dies.
Authors: Saeed Bikass, Bjørn Andersson, Xiang Ma
Abstract: Cooling subsequent to extrusion is a crucial process in aluminum extrusion value chain. Non-uniform cooling-induced shape distortion, such as deflection, twisting and etc., is a challenge for extrusion profile manufacturers. Temperature management is therefore a key to the aluminum extrusion process. Appropriate modeling, using both physical and numerical methods, can help us achieve a better temperature control in extrusion plants. In this work, finite element (FE) method was used to simulate shape distortion due to cooling and the most important challenge was to make FE models compatible to real conditions in plants. The effects of three important items I) mechanical boundary condition II) cooling source type and III) effective cooling length were examined. It was shown that for compatible prediction of distortions it was necessary to define these items similar to real life. It was also revealed that with a suitable definition of boundary conditions it is possible to use a short lab scale sample to understand mechanisms in real life profiles.
Authors: Dan Mândru, Ion Lungu, Simona Noveanu, Mihai Olimpiu Tătar
Abstract: The first part of the paper treats the general problems concerning the shape memory alloy actuators and their operation principle. Then, our work referring to the developing a modular family of linear and rotational actuators, realized in many typo dimensions, in a compact design, with facile connection with the actuated mechanisms and supplying module is presented. The active elements of these actuators are shape memory alloy wires, ribbons and helical springs. The influence of the geometry of the active elements on the time response is studied. The most important solutions to reduce the resistive heating time of active elements and to improve the time response on cooling are identified.
Authors: G. Gabrielse, W. Jhe, D. Phillips, R. Kaiser, H. Kalinowsky, J. Gröbner
Authors: Xin Qi Yu, Zhi Xu, Qing Gang Liu, Dong Dong Yuan, Jia Hui Yu
Abstract: A small indoor cooling system through cold water circulation is introduced in this paper. The system mainly includes cooling pool, cold water circulation equipment, indoor heat exchanger, temperature measurement equipment and induction controlling equipment. The indoor cooling is achieved by heat transfer between the natural underground water of lower temperature and indoor air of higher temperature, and it is different from the traditional compression refrigeration system in which a great amount of electric energy is consumed while the refrigerant is compressed. Compared with the ordinary air conditioning system, this system has obvious advantages on economy, application potential and energy conservation in rural developing areas.
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