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Full-Text Articles in Engineering Science and Materials

Modeling Of The Transient Behavior Of Heat Pipes With Room-Temperature Working Fluids, Pascal Brocheny Dec 2006

Modeling Of The Transient Behavior Of Heat Pipes With Room-Temperature Working Fluids, Pascal Brocheny

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The heat pipe is a capillary-driven and two-phase flow device, capable of transporting and converting large amounts of energy with minimal losses. As a means of thermal management, uses of heat pipe technology not only include thermal control of satellites and spacecrafts in aerospace applications, but also the cooling of electronic components for ground applications. Recently, there has been a flourishing interest in exploring the use of heat pipe technology in the automotive field. However, in many thermal control applications, heat pipes using room-temperature working fluids, such as water or ammonia, with operating temperatures between 200 K (-73ºC) and 550 …


A Robust Conjugate Heat Transfer Methodology With Novel Turbulence Modeling Applied To Internally-Cooled Gas Turbine Airfoils, William York Dec 2006

A Robust Conjugate Heat Transfer Methodology With Novel Turbulence Modeling Applied To Internally-Cooled Gas Turbine Airfoils, William York

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Computational fluid dynamics and heat transfer (CFD) has become a viable, physics-based analysis tool for complex flow and/or heat transfer problems in recent years due, in large part, to rapid advances in computing power. CFD based on the Reynolds-averaged Navier-Stokes (RANS) equations is starting to enter the mainstream design environment in certain industries where rapid and reliable predictive capability is necessary. One such application is the gas turbine industry, where thermal management of airfoils at extremely high temperatures is one of the most critical components in engine design for reliability. The problem is complicated by the need for advanced airfoil …


Investigation Of The Effects Of Subgrid-Scale Turbulence On Resolvable-Scale Statistics, Qinglin Chen Dec 2006

Investigation Of The Effects Of Subgrid-Scale Turbulence On Resolvable-Scale Statistics, Qinglin Chen

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The effects of the subgrid-scale (SGS) turbulence on the resolvable-scale statistics and the effects of SGS models on large-eddy simulation (LES) are studied. It is shown that the SGS turbulence evolves the resolvable-scale joint probability density function (JPDF) through the conditional means of the SGS stress, the SGS scalar flux, and their production rate, which must be reproduced by the SGS model for LES to predict correctly the one-point resolvable-scale statistics, a primary goal of LES. This necessary condition is used as the basis for studying SGS physics and for testing SGS models. Theoretical predictions, measurements data obtained in a …


Modeling And Simulation Of Friction-Limited Continuously Variable Transmissions, Nilabh Srivastava Dec 2006

Modeling And Simulation Of Friction-Limited Continuously Variable Transmissions, Nilabh Srivastava

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Over the last few decades, a lot of research effort has increasingly been directed towards developing vehicle transmissions that accomplish the government imperatives of increased vehicle efficiency and lower exhaust (greenhouse gaseous) emissions. These exhaust emissions can be regulated or lowered by increasing the fuel economy of a vehicle, and CVTs (continuously variable transmissions), indubitably, play a crucial role in this plan to improve the fuel economy. A continuously variable transmission is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. A CVT offers numerous advantages over the conventional multi-step gear transmissions such as …