Papers by Keyword: Heat Transfer Coefficient (HTC)

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Authors: Chao Wang, Zhong Hai Yin, Xue Jun Chen
Abstract: In the field of architecture, “energy-saving building” has been mentioned as a strategy which is as important as the ones of our population, resources, environment and sustainable development. The design of the building wall materials in the building envelope is the key step of the wall insulation, which can be taken as the key technology in building energy efficiency. Tests, starting from the thermal characteristics of the building envelope and the raw materials, taking heat transfer coefficient as an important parameter, show that the polystyrene particulate composite silicate thermal insulation material can be designed to meet energy-saving requirements.
Authors: Josée Colbert, Dominique Bouchard
Abstract: A heat transfer model was built to predict the temperature evolution of semi-solid aluminum billets produced with the SEED process. An inverse technique was used to characterize the heat transfer coefficient at the interface between the crucible and the semi-solid billet. The effect of several process parameters on the heat transfer coefficient was investigated with a design of experiments and the coefficient was inserted in a computer model. Numerical simulations were carried out and validated with experimental results.
Authors: Jeong Tae Kim, Chae Ho Lim, Jeong Kil Choi, Young Kook Lee
Abstract: New method for evaluation of heat transfer coefficient is proposed. In general, many researchers have been studied about inverse problem in order to calculate the heat transfer coefficient on three-dimensional heat conduction problem. But they can get the time-dependent heat transfer coefficient only through inverse problem. In order to acquire temperature-dependent heat transfer coefficient, it requires much time for numerous repetitive calculation and inconvenient manual modification. In order to solve these problems, we are using the SQP(Sequential Quadratic Programming) as an optimization algorithm. When the temperature history is given by experiment, the optimization algorithm can evaluate the temperature-dependent heat transfer coefficient with automatic repetitive calculation until difference between calculated temperature history and experimental ones is minimized. Finally, temperature-dependent heat transfer coefficient evaluated by developed program can used on the real heat treatment process of casting product.
Authors: Zhong Lin Hou, Ting Li, Jun Qiao, Sheng Li Li
Abstract: The heat transfer coefficient between the alloys and cooling water is affected by a lot of factors and hard to measure, a new method was investigated with a self-designed system ultilizing SP-15 high-frequency inductive heating unit. Based on measured temperature curves and Fourier heat transfer model, quantitative correlation between heat transfer coefficient and temperature was obtained by inverse algorithm method of iterative simulation and automatic optimization. The results showed that in submerged water-cooling process, the heat transfer coefficient reached to a peak value at the beginning and then decreased with increasing temperature. A decrease of cooling water temperature increased the peak value of the heat transfer coefficient, but did not change temperature range of the peak value from 200°C to 225°C . The heat transfer coefficient was mainly dependent of interfacial temperature between the Al-Cu alloys and the cooling water.The temperatures range from 200°C to 225°C gave the highest heat flux transfer.
Authors: Ho Dong Yang, Yool Kwon Oh
Abstract: The present study was experimentally investigated the effect of ultrasonic vibrations on boiling heat transfer augmentation during the heating process. The experiments were carried out under the constant wall temperature condition and were divided into two cases applying with and without ultrasonic vibrations, respectively. Also, the temperature distributions in a vessel filled with water were measured using thermocouples during the heating process, heat transfer coefficient and augmentation ratio of heat transfer on states of convection, subcooled boiling and saturated boiling were calculated from obtained temperature profiles. In addition, the profiles of pressure variations measured using a hydrophone were compared with the augmentation ratio of heat transfer in acoustic fields. The results of experimental study were revealed that general profiles of heat transfer coefficient and augmentation ratio of heat transfer is more increased the convection state than the others states. Moreover, the profiles of acoustic pressure is relatively higher near ultrasonic transducer than other points where is no installed it and affects the augmentation ratio of heat transfer. In the end, as well as known “acoustic streaming” induced by ultrasonic vibrations is one of the prime effects acoustically augmented boiling heat transfer or phase change heat transfer.
Authors: Feng Bo Qu, Wei Li Li, Ting Ting Chen, Zhi Peng Li
Abstract: Taking a 315kW, 6kV permanent magnet synchronous motor (PMSM) with solid rotor as an example, the physical and mathematical models of PMSM three dimensional temperature fields analysis are established according to the heat transfer principles. The basic hypothesis and boundary value problems of the solving region in the motor are also presented. The 3-D temperature field in stator of PMSM was calculated, and the influences of heat transfer coefficients with consideration of the axial wind or not on stator temperature were analyzed. By comparing the test results with the calculated results, the influences of axial wind on motor temperature were investigated. These conclusions provide a reference for thermal design of the motor with co-axial fan and enclosure cooling fan.
Authors: Tao He, Xi Qun Lu, Yi Bin Guo
Abstract: An efficient method utilizing the concept of inverse heat conduction is presented for the thermal analysis of pistons based on application to the piston head of a marine diesel engine. An inverse heat conduction problem is established in the form of an optimization problem. In the optimization problem, the convection heat transfer coefficient(HTC)on the top side of the piston is defined as the design variable, while the error between the measured and analysed temperatures is defined as objective function. For the optimization, an axi-symmetrical finite element conduction model is presented. The optimum distribution of the HTC at the top side of piston is successfully determined through a numerical implementation. The temperature obtained via an analysis using the optimum HTC is compared with the measured temperature, and reasonable agreement is obtained. The present method can be effectively utilized to analyze the temperature distribution of engine pistons.
Authors: Zheng Li, Hong Wu Zhu, Pin Xian Qiu, Abdennour Seibi
Abstract: HDPE pipes have been widely used in industry, which were mostly buried underground. Because of special material properties, which were affected by temperature, it is necessary to get the temperature profile of buried HDPE pipe. Most past solutions for temperature distribution in buried pipe were numerical ones. The aim of this paper was to present a simple analytical model under steady-state heat transfer condition with a new special heat transfer coefficient introduced. FEM method was used to check this model. The influences of fluid temperature, soil surface temperature and soil depth on pipeline temperature were also analyzed. The results showed a good agreement between the analytical model and FEM method. And fluid temperature in pipe was proved to be the key factor that affected the pipe temperature .
Authors: S.M. Sohel Murshed, C.A. Nieto de Castro, M.J.V. Lourenço, M.L.M. Lopes, F.J.V. Santos
Abstract: Nanofluids have attracted great interest from researchers worldwide because of their reported superior thermal performance and many potential applications. However, there are many controversies and inconsistencies in reported experimental results of thermal conductivity, convective heat transfer coefficient and critical heat flux of nanofluids. In this paper, two major features of nanofluids, which are boiling and convective heat transfer characteristics are presented besides critically reviewing recent research and development on these areas of nanofluids.
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