共查询到20条相似文献,搜索用时 239 毫秒
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双金属轧片式翅片管管外对流换热准则关系式研究 总被引:1,自引:0,他引:1
双金属轧制翅片管以其优良的传热性能、机械性能和耐腐蚀性能在许多工业领域,特别是炼油、化工、发电行业得到了广泛应用。影响双金属轧片式翅片管的传热性能的一个重要因素是管外气体一侧的对流换热系数。本文对双金属轧片式翅片管管外对流换热系数准测进行了研究,得到了一个精度较高的适用于各种规格双金属轧片式翅片管的通用的管外对流换热系数准则关系式。 相似文献
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翅片管换热器是高效节能钢带式果蔬绿色干燥装备的供热装置,通过对翅片管换热器的翅化比、对流换热系数、传热系数及阻力的计算,得到了翅片管换热器的压降及翅片管的管数,计算结果表明翅片管换热器换热能力强,传热系数高。 相似文献
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《机械工程与自动化》2017,(5)
考虑了闸片形状对制动盘摩擦面上热流密度分布的影响,利用微元法计算热输入模型,将辐射换热系数折算成等效对流换热系数,建立了高速列车制动盘的有限元分析模型,并利用ANSYS对制动盘制动过程中温度场的分布进行了仿真分析。 相似文献
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液压系统油液温升取决于其生热和换热速率,对流换热系数是液压系统散逸热量精确计算的关键,也是液压系统热分析难点之一。首先介绍了对流换热系数测量和计算方法的发展,然后对目前工程上对流换热系数的测量和计算方法进行概述,分析了这些方法的优缺点、适用范围及发展前景,为液压系统对流换热系数的准确测量与计算提供借鉴。 相似文献
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低沸点工质在水平蒸发换热强化管内换热特性研究 总被引:3,自引:0,他引:3
本文通过分析作者和国内外文献有关低沸点工质在水平螺旋翅片管内蒸发换热特性实验数据,讨论了热流密度,质量干度和质量流速对局部换热系数的影响,并将实验数据与现有的螺旋翅片管换热关系式的计算值进行比较,结果表明,kandlikar的关系式具有是确的流动沸腾换热机制及一定的精度。为提高其通用性和精度,本文提出了进下不改进Kandlikar关系式的具体设计想,从而为优化设计螺旋翅片管,研制高效蒸发强化管提代 相似文献
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机床主轴温度场分析是一种减少主轴热误差、提高主轴精度及其稳定性的重要方法。作为热分析边界条件中关键参数的对流换热系数,其值大小反映了主轴零部件表面与空气对流换热的强度,对主轴有限元温度场分析结果的影响最为明显。以170CP06-DM机械主轴为研究对象,深入研究主轴对流换热系数的影响因素,提出一种基于人工蜂群优化算法的机床主轴换热系数优化算法。实验表明,提出的蜂群算法能够根据环境温度和转速而自动寻找优化的主轴换热系数。与传统的经验确定对流换热系数方法相比,主轴前轴承处的计算最大误差、平均误差、均方差分别提高了大约4.54℃、2.87℃、1.65℃,主轴后轴承处的计算最大误差、平均误差、均方差分别提高了大约7.12℃、3.49℃、2.41℃。 相似文献
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Armin Rahmati Darvazi Mehdi Iranmanesh 《The International Journal of Advanced Manufacturing Technology》2014,75(9-12):1299-1307
This paper presents a numerical model, based on the displacement of one point of the material flow relative to a fixed reference point, in order to formulate the heat generation during friction stir process and thereby calculate the temperature difference between advancing and retreating sides. This model considers frictional heating dependent on both the temperature and the velocity of the tool, as well as heat generation due to plastic deformation dependent on temperature, and assumes that friction heat at high temperature was replaced by heat generation due to plastic deformation. The heat generated by plastic strain energy dissipation in thermomechanically affected zone is calculated by a new technique, and the convection heat transfer coefficient and the sticking state parameter are considered as a function of temperature. Finally, the thermal equations are solved using a nonlinear finite element code ABAQUS. The numerical results correctly showed the asymmetric nature of temperature distributed at different sides of the weld line which have good agreement with experimental data that are presented in the literature. 相似文献
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Kyung-Beom Yoon Won-Hee Park Tae-Kuk Kim 《Journal of Mechanical Science and Technology》2013,27(6):1575-1580
Data for the convection heat transfer coefficient and the surface emissivity of a matter are not easily available from the literature and are usually assumed to be constant values in most studies of pyrolysis. In this study the convection heat transfer coefficient and the surface emissivity of a specimen placed within a cone calorimeter under different external heat fluxes are estimated by using the statistical repulsive particle swarm optimization (RPSO) method. The transient surface temperature distribution of the specimen are measured from the cone calorimeter experiments for different external heat fluxes and these data are then used to determine the convection heat transfer coefficient and the surface emissivity of the specimen inversely. To check the accuracy of this method, we compared the measured temperature and the recalculated temperature of the specimen by using the estimated convection heat transfer coefficient and surface emissivity and we confirmed that they were fairly well matched with each other. We conclude that the proposed RPSO method of estimating the convection heat transfer coefficient and surface emissivity can be an alternative way of obtaining these data for various fire analyses. 相似文献
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In this paper, the evaluation of a measurement method is discussed which can determine the heat transfer coefficient in convection reflow ovens. Nowadays the reflow ovens apply forced convection heating with nozzle-matrix blower system. In these ovens the heat transfer coefficients of the heater gas streams determine mainly the efficiency of heating. A method is presented which has two steps: in the first step, the heat transfer coefficient of the heater gas streams is studied above the assembly in function of height; in the second step, the heating efficiency of the nozzle-lines is compared as a distribution of the heat transfer coefficient in the oven. The heat transfer coefficients are calculated from the heat equation of the reflow oven. It is also presented with the distributions of the heat transfer coefficient that how the contamination of the nozzles affects the heating efficiency of the reflow oven. 相似文献
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Efficiency analysis of straight fin with variable heat transfer coefficient and thermal conductivity
Sadri Somayyeh Raveshi Mohammad Reza Amiri Shayan 《Journal of Mechanical Science and Technology》2012,26(4):1283-1290
In this study, one type of applicable analytical method, differential transformation method (DTM), is used to evaluate the
efficiency and behavior of a straight fin with variable thermal conductivity and heat transfer coefficient. Fins are widely
used to enhance heat transfer between primary surface and the environment in many industrial applications. The performance
of such a surface is significantly affected by variable thermal conductivity and heat transfer coefficient, particularly for
large temperature differences. General heat transfer equation related to the fin is derived and dimensionalized. The concept
of differential transformation is briefly introduced, and then this method is employed to derive solutions of nonlinear equations.
Results are evaluated for several cases such as: laminar film boiling or condensation, forced convection, laminar natural
convection, turbulent natural convection, nucleate boiling, and radiation. The obtained results from DTM are compared with
the numerical solution to verify the accuracy of the proposed method. The effects of design parameters on temperature and
efficiency are evaluated by some figures. The major aim of the present study, which is exclusive for this article, is to find
the effect of the modes of heat transfer on fin efficiency. It has been shown that for radiation heat transfer, thermal efficiency
reaches its maximum value. 相似文献
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为提高水冷盘式制动器散热性能,基于强化对流传热原理,通过添加扰流柱对制动器散热结构进行优化,设计了4种扰流柱散热结构,运用CFD方法模拟制动盘流固耦合传热过程,采用Fluent软件进行热流固耦合仿真计算,获得制动盘温度特性和换热特性以及流动阻力特性,并使用综合性能评价因子对不同扰流柱散热结构进行评价。结果表明:通过在安装盘水槽内添加扰流柱可以有效地提高水冷盘式制动器的散热效果;在相同的工作条件下,正三角形扰流柱散热结构的盘面温度最低,平均努塞尔数与流动阻力最高,其综合散热性能较圆形、椭圆形以及水滴形扰流柱散热结构分别提高了3.4%,2.4%和4.4%,较无扰流柱散热结构提高了6.7%,正三角形扰流柱散热结构具有更好的综合散热性能。研究结果为水冷盘式制动器散热结构的优化设计提供了参考。 相似文献
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Waqar A. Khan Rama Subba Reddy Gorla 《Journal of Mechanical Science and Technology》2010,24(9):1919-1925
The mixed convection of power-law fluids along a wedge in a porous medium is investigated numerically using an implicit finite
difference method. Robin boundary condition is applied at the wedge surface. To explore the effects of mixed convection, both
forced and free convection dominated regimes are considered separately. Non-similarity solutions are obtained for the variable
heat transfer coefficient. Local dimensionless skin friction and Nusselt number are presented in tabular and graphical forms
for the selected values of wedge and convective parameters. The wedge angle geometry parameter r m, power index of pseudoplastic fluids n and mixed convection parameter ξ range from 0 to 1 in both regimes, whereas different values of convective parameter h
c
are considered for investigating the behavior of skin friction and heat transfer rates. 相似文献
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Chang-Yong Choi 《Journal of Mechanical Science and Technology》2006,20(12):2230-2241
This paper presents a sole application of boundary element method to the conjugate heat transfer problem of thermally developing
laminar flow in a thick walled pipe when the fluid velocities are fully developed. Due to the coupled mechanism of heat conduction
in the solid region and heat convection in the fluid region, two separate solutions in the solid and fluid regions are sought
to match the solid-fluid interface continuity condition. In this method, the dual reciprocity boundary element method (DRBEM)
with the axial direction marching scheme is used to solve the heat convection problem and the conventional boundary element
method (BEM) of axisymmetric model is applied to solve the heat conduction problem. An iterative and numerically stable BEM
solution algorithm is presented, which uses the coupled interface conditions explicitly instead of uncoupled conditions. Both
the local convective heat transfer coefficient at solid-fluid interface and the local mean fluid temperature are initially
guessed and updated as the unknown interface thermal conditions in the iterative solution procedure. Two examples imposing
uniform temperature and heat flux boundary conditions are tested in thermally developing region and compared with analytic
solutions where available. The benchmark test results are shown to be in good agreement with the analytic solutions for both
examples with different boundary conditions. 相似文献
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Study on the convection heat transfer coefficient of coolant and the maximum temperature in the grinding process 总被引:1,自引:1,他引:0
B. Lin M. N. Morgan X. W. Chen Y. K. Wang 《The International Journal of Advanced Manufacturing Technology》2009,42(11-12):1175-1186
Grinding fluid is typically applied in order to achieve reduced surface grinding temperatures, improved workpiece surface integrity, and extended wheel life compared to that which can be achieved in the dry situation. This paper presents the results of an investigation concerned with methods to determine the value of the convection heat transfer coefficient. The work is based on the theory of fluid dynamics and heat transfer that are used to describe the heat transfers within the grinding zone under different grinding conditions. The simulation research is made by means of the FEM for the wet grinding temperature distribution, and the three-dimensional topology map of the temperature distribution is obtained. Temperature is measured with the clamped thermocouple in different grinding conditions. The experimental result is approximately suitable to the simulated result. The simplicity and accuracy of the method allow the application to a wide range of grinding regimes from shallow-cut to high-efficiency deep grinding. 相似文献