Papers by Keyword: Heat Transfer

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Authors: Stefan Mihić, Sorin Cioc, Ioan Marinescu, Michael C. Weismiller
Abstract: Fluids have an important role in grinding. Correct fluid application results in enhanced process stability, better work piece quality, and tool life. This paper shows that Computational Fluid Dynamics (CFD) models can be used to simulate the fluid flow and heat transfer in a grinding process, replacing numerous experiments that are expensive, time-consuming, and have limited capabilities. The most important properties of created 3-D model are described, along with results obtained. The results show very detailed distributions of temperatures, pressures, and flow rates in and around the grinding region. The data obtained is essential in studying the influence of the grinding fluid on the grinding process, as well as in determining the best fluid composition and supply parameters for a given application. The results agree well with experimental global flow rates and temperature values and show the feasibility of 3-D CFD-based simulations in grinding applications. The parametric studies of influence of several fluid physical properties on useful flow rates and temperatures were presented as well.
Authors: Jiin Yuh Jang, Jia Yan Wu, Shang Hua Tsai
Abstract: This study presents heat transfer rate and temperature distributions for the prediction of each component in an air-cooled motorcycle engines. The 3-D finite element method was used to solve the temperature field and heat transfer rate for each component (intake valves, exhaust valves, piston, piston rings, cylinder head and cylinder) of motorcycle engine when the piston is in TDC and BDC. The results shows that the fractions of heat transfer rate for each component are as follows: intake valves 11%, exhaust valves 8%, cylinder head 21%, the piston 35% and the cylinder 25%. And the temperature measurement value is in good agreement with experimental data within 20%.
Authors: Feng Zhi Li, Yi Li, Mou Guang Lin
Abstract: A 3-D heat and moisture transfer model for the human-clothing-environment system (HCES) is developed. The Smith-Fu’s finite element model is improved by considering more real 3-D geometry properties of the human body. Meanwhile, the heat and moisture transfer mechanisms, including water vapor diffusion, the moisture evaporation/condensation, moisture sorbtion/ desorption by fibers, and latent heat absorption/release due to phase change, are considered in a new 3-D clothing model. The clothed human body model predictions are compared with published experimental data at a variety of ambient conditions. The model predictions agree well with the experimental data, indicating that the present model has good prediction ability. Also, the model predictions are given by using the 3-D Figures.
Authors: Amnart Boonloi, Withada Jedsadaratanachai, Pongjet Promvonge
Abstract: This work deals with periodic flow, friction loss and heat transfer characteristics in a constant temperature-surfaced circular tube fitted with rib vortex generators (RVG). The computations are based on the finite volume method with the SIMPLE algorithm implemented. The fluid flow and heat transfer behaviors are presented for Reynolds numbers ranging from 100 to 1000. To generate two main vortex flows through the tested section, the 45o RVGs are mounted repeatedly in in-line arrangements on the top and bottom walls and in the central area of the tested section. Effects of different RVG heights, BR in a range from 0.1D to 0.3D with a single pitch of 1.5D on heat transfer and friction losses in the test section are examined. It is apparent that the vortex flows created by the RVG exist and help to induce periodically impinging flows on a sidewall leading to drastic increase in the heat transfer rate over the test section. The computational results reveal that the optimum thermal performance is about 2.38 for using the RVG height of 0.2D for the RVG placed on the tube walls at the highest Re value.
Authors: Estaner Claro Romão
Abstract: This paper aims in particular to do a case study of the numerical efficiency of the application of LSFEM (Least Squares Finite Element Method) in the solution of heat conduction problems in multi-connected domains. To demonstrate this study two cases (the first with exact solution for comparison of results) are presented in the same multi-connected geometry, of easy construction, to facilitate the comparison of the results of this paper with future studies of other researchers.
Authors: Seok Jae Lee, Young Kook Lee
Abstract: A coupled model for predicting phase transformation, temperature, and distortion of AISI 5120 steel occurring during heat treatment process has been developed. The phase transformation kinetic models were made using Johnson-Mehl-Avrami equation and the additivity rule based on theoretical thermodynamic model and experimental dilatometric data. Especially, the transformation strains measured during cooling were converted to the volume fraction of each phase for the kinetic models using a relation between transformation strain and atomic volume change. The heat transfer coefficients in quench media were calculated by inverse method of the heat transfer equation to the measured surface temperature history. To predict the temperature and distortion accurately, the thermal and mechanical data were used as a function of temperature and each phase based on the experimental data. The coupled model for phase transformation, temperature, and distortion has been implemented in the commercial finite element software ABAQUS as user subroutines. The calculated results by the coupled model were compared with the experimental ones.
Authors: Qi Zhang, La Dao Yang
Abstract: A model of heat transfer and solidification of continuous cast has been established, including boundary conditions in the mold and spray zones. A finite difference method was used for the numerical simulation. The model calculates the shell thickness and temperature distributions of the slab real time. The importance effect of non-linear material properties of specific heat and thermal conductivity as well as phase changes during solidification is treated. The adequacy of model has been proved by industrial and experimental data. The model can be applied to solve some practical problems in continuous cast.
Authors: Yun Fu Chen
Abstract: For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.
Authors: Jing Hong Yao
Abstract: Vacuum is an important economic indicator of influencing turbine load and thermal efficiency. And heat transfer efficiency affects the level of vacuum directly. From the point of heat transfer analysis, combining with the production practice in a power plant, this paper proposes a method of improving heat transfer effectiveness and the condenser exchanging condition. Through the method of reducing the heat load of condenser, improving the tightness of the vacuum system, cleaning the heat surface and reducing the cooling water temperature, we improve the vacuum and reach the aim of energy saving.
Authors: Qi Zhang, La Dao Yang, Heng Wen
Abstract: A two-dimensional (2-D) heat transfer and solidification model has been established and applied to calculate the temperature distribution and solid shell thickness profile of a continuous casting slab in a steel plant. A finite difference method was used for the numerical simulation. For thermal analysis, the 2-D slice unsteady-state heat conduction equation with enthalpy convention was used. Meanwhile, non-linear material properties of specific heat and thermal conductivity as well as phase changes during solidification were considered in the model. The temperature distribution and solid shell thickness calculated by mathematical model agree with those predicted by industrial and experimental measurements. The model could also be used to predict the optimum process parameters on casting speed, heat removal rates and the water distribution of secondary cooling zone.
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