From a microscopic point of view, the process of heat transport is governed by phonon-electron interaction in metallic films and by phonon scattering in dielectric films, insulators, and semiconductors. Other include the, andThe Open Library website has not been optimized for Internet Explorer 6, so some features and graphic elements may not appear correctly. Many sites, including and Facebook, have phased out support for IE6 due to security and support issues. Please consider upgrading to,,,, or to use this and other web sites to your fullest advantage. No es necesario ningún dispositivo Kindle. Descárgate una de las apps de Kindle gratuitas para comenzar a leer libros Kindle en tu smartphone, tablet u ordenador.
Haz que tu cesta sea útil: llénala de libros, DVD, productos electrónicos y mucho más. Hay un problema para ver una vista previa de tu carro de la compra en este momento. In this equation h is the heat transfer coefficient of the microscale heat exchanger, Nu is the Nusselt number which is about 8. 65, k is the thermal conductivity of the working fluid and d is the diameter of the microchannel which the fluid flows through. From this equation one can tell see how the size of the channel directly affects the heat transfer coefficient of the heat exchanger, as the diameter is decreased the heat transfer coefficient increases. The different types of microscale heat exchangers are the same as the different classifications of conventional heat exchangers.
They have either one or two passages for the fluid to flow through. When there is only one fluid and one passage in the heat exchanger the fluid is used to transfer the heat to another location. Application of this kind of heat exchangers is usually found in electronics to transfer heat into the fluid and out of the electronic device. When there are two fluids and two passages they are usually classified by the direction in which the fluids flow by each other. Microscale heat exchangers can either be cross flow or counter flow heat exchangers. Counter flow micro scale heat exchangers work the same way as macro-scale counter flow heat exchangers. In a counter flow heat exchanger the two fluids flow in opposite directions of each other.
The fluids enter the heat exchanger at opposite ends. The cooler fluids exits the counter flow microscale heat exchanger at the end where the hot fluid enters therefore the cooler fluid will approach the inlet temperature of the hot fluid. Counter flow microscale heat exchangers are more efficient than cross flow microscale heat exchangers. Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM 87686A universal constitutive equation between the heat flux vector and the temperature gradient is proposed to cover the fundamental behaviors of diffusion (macroscopic in both space and time), wave (macroscopic in space but microscopic in time), phonon–electron interactions (microscopic in both space and time), and pure phonon scattering. The model is generalized from the dual-phase-lag concept accounting for the lagging behavior in the high-rate response. While the phase lag of the heat flux captures the small-scale response in time, the phase lag of the temperature gradient captures the small-scale response in space. The universal form of the energy equation facilitates identifications of the physical parameters governing the transition from one mechanism (such as diffusion or wave) to another (the phonon–electron interaction).
Sign in or create your free personal ASME account. This will give you the ability to save search results, receive TOC alerts, RSS feeds, and more. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required. Physical processes taking place in micro/nanoscale strongly depend on the material types and can be very complicated. Known approaches include kinetic theory and quantum mechanics, non-equilibrium and irreversible thermodynamics, molecular dynamics, and/or fractal theory and fraction model. Due to innately different physical bases employed, different approaches may involve different physical properties in describing micro/nanoscale heat transport. In addition, the parameters involved in different approaches, may not be mutually inclusive.
Macro- to Microscale Heat Transfer: The Lagging Behavior, Second Edition continues the well-received concept of thermal lagging through the revolutionary approach that focuses on the finite times required to complete the various physical processes in micro/nanoscale. Different physical processes in heat/mass transport imply different delay times, which are common regardless of the material type.