The effect of perforation sizes on laminar heat transfer characteristics of an array of perforated fins
- Authors: Shaeri, Mohammad Reza , Jen, Tien-Chien
- Date: 2012
- Subjects: Perforated fins , Heat transfer , Laminar convection
- Type: Article
- Identifier: uj:5285 , http://hdl.handle.net/10210/14954
- Description: Shaeri and Yaghoubi [25] reported the highest heat transfer rate in a laminar flow for a perforated fin with the most perforations (porosity), regardless of investigation on the effects of perforation sizes. In this study, the effects of size and number of perforations on laminar heat transfer characteristics of an array of perforated fins at the highest porosity of the study of Shaeri and Yaghoubi [25] have been numerically investigated. The Navier–Stokes and energy equations are solved by the finite volume procedure using the SIMPLE algorithm. Results show that at a specific porosity, the thermal entrance length of each perforation of a fin with a lower number of perforations is larger than that of each perforation of a fin with a higher number of perforations. Therefore, in a laminar flow and at a constant porosity, a fin with fewer perforations is more efficient to enhance the heat transfer rate compared with a fin with more perforations. Although perforated fins have higher friction drag and lower pressure drag with respect to solid fins, perforated fins do not affect total drag.
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Thermal analysis of the grinding process
- Authors: Gu, R. J. , Shillor, M. , Barber, G. C. , Jen, T.
- Date: 2004
- Subjects: Grinding , Heat transfer
- Type: Article
- Identifier: uj:5262 , http://hdl.handle.net/10210/14931
- Description: A two-dimensional mathematical model for the thermal aspects of a grinding process is presented. The model includes heat conduction in the grinding wheel, workpiece, and coolant. The heat generation through friction, heat loss to the environment as well as debris, and the interaction among the three components are described in detail. A finite-element algorithm is implemented to solve the nonlinear problem. Numerical results, such as temperatures in the grinding wheel and workpiece, are presented.
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Thermal aspect of grinding : heat transfer to workpiece, wheel, and fluid
- Authors: Lavine, A.S , Jen, T.-C.
- Date: 1991
- Subjects: Grinding , Heat transfer , Workpiece burn
- Type: Article
- Identifier: uj:5255 , http://hdl.handle.net/10210/14924
- Description: Please refer to full text to view abstract
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Thermo-chemical characteristics of R134a flow boiling in helically coiled tubes at low mass flux and low pressure
- Authors: Chen, Chang-Nian , Han, Ji-Tian , Jen, Tien-Chien , Shao, Li
- Date: 2011
- Subjects: Helically coiled tubes , Heat transfer , Low mass flux , Low pressure
- Type: Article
- Identifier: uj:5282 , http://hdl.handle.net/10210/14951
- Description: The characteristics of R134a heat transfer coefficients and wall temperature distribution were investigated under low mass flux and low pressure conditions in a helically coiled tube with heated length of 7070mm, outer diameter of 10mm, inner diameter of 7.6mm, coil diameter of 300mm and helical pitch of 40mm. System pressures, mass fluxes and inlet qualities range from 0.20 to 0.75 MPa, 50 to 260 kg/m2 s and −0.18 to 0.40, respectively. It was found that the wall temperatures in descending segments of coiled tube were higher than those of climbing ones, while the heat transfer coefficients varied inversely. Around the section circumference, the outside temperature was lower than the inside one; this is more apparent at very low mass flux and pressure conditions. The heat transfer coefficient increases with increasing mass flux, vapor quality and heat flux. However, the pressure has an indeterminate effect. New heat transfer coefficient correlations for current conditions were developed comparing with existing correlations.
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Transient heat transfer analysis on a heat pipe with experimental validation
- Authors: Gutierrez, Gustavo , Catano, Juan , Jen, Tien-Chien , Liao, Quan
- Date: 2006
- Subjects: Numerical analysis , Heat transfer , Heat pipes
- Type: Article
- Identifier: uj:5270 , http://hdl.handle.net/10210/14939
- Description: In this study, a transient analysis of the performance of a heat pipe with a wick structure is performed. A complete formulation of the equation governing the operation of a heat pipe during transient conditions are presented and discussed. For the vapor flow, the conventional Navier-Stokes equations are used. For the liquid flow in the wick structure, which is modeled as a porous media, volume averaged Navier-Stokes equations are adopted. The energy equation is solved for the solid wall and wick structure of the heat pipe. The energy and momentum equations are coupled through the heat flux at the liquid-vapor interface that defines the suction and blowing velocities for the liquid and vapor flow. The evolution of the vaporliquid interface temperature is coupled through the heat flux at this interface that defines the mass flux to the vapor and the new saturation conditions to maintain a fully saturated vapor at all time. A control volume approach is used in the development of the numerical scheme. A parametric study is conducted to study the effect of different parameters that affect the thermal performance of the heat pipe. And experimental setup is developed and numerical res ults are validated with experimental data. The results of this study will be useful for the heat pipe design and implementation in processes that are essentially transient.
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Turbulent heat transfer analysis of a three-dimensional array of perforated fins due to changes in perforation sizes
- Authors: Jen, T.C , Shaeri, Mohammad Reza , Jen, Tien-Chien
- Date: 2012
- Subjects: Heat transfer , Perforated fins
- Type: Article
- Identifier: uj:5261 , ISSN 1040-7782 , http://hdl.handle.net/10210/14930
- Description: Turbulent heat transfer characteristics of three-dimensional and rectangular perforated fins, including perforation like channels along the length of the fins, are investigated. Both dimensions and numbers of perforations are changed at the highest porosity in the study of Shaeri and Yaghoubi [7] to determine the effects of perforation sizes on the heat transfer characteristics of the perforated fins. Results show that at a specific porosity, a fin with a higher number of perforations enhances the heat transfer rate more efficiently. Also, total drag is not only remarkably lower in perforated fins compared with a solid fin, but also becomes smaller by decreasing the number of perforations.
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