Heating, microscale

Duncan AB, Peterson GP (1994) Review of microscale heat transfer. Appl Mech Rev 47 397 28... 

Recent inventions in micro and nano-scale systems and the development of micro and nano-scale devices continues to pose new challenges, and the understanding of the fluid flow and heat transfer at such scales is becoming more and more important. In Chapter 6, microscale heat transfer is presented as a Topic of Special Interest. 

Heat transfer considerations play a crucial role in the design and operation of many modern devices. New approaches and methods of analyses have been developed to understand and modulated (enhance or suppress) such energy interactions. Modulation typically occurs through actively controlling the surface phenomena, or focusing of the volumetric energy. In this section we discuss one such example microscale heat transfer. 

The conventional macroscopic Fourier conduction model violates this non-local feature of microscale heat transfer, and alternative approaches are necessary for analysis. The most suitable model to date is the concept of phonon. The thermal energy in a uniform solid material can be jntetpreied as the vibrations of a regular lattice of closely bound atoms inside. These atoms exhibit collective modes of sound waves (phonons) wliich transports energy at tlie speed of sound in a material. Following quantum mechanical principles, phonons exhibit paiticle-like properties of bosons with zero spin (wave-particle duality). Phonons play an important role in many of the physical properties of solids, such as the thermal and the electrical conductivities. In insulating solids, phonons are also (he primary mechanism by which heal conduction takes place. 

S. Kakag et al. (eds.), Microscale Heat Transfer, 1-24. 2005 Springer. Printed in the Netherlands. 

A NATO Advanced Study Institute was held, between July 18 - 30, 2004, in Qe me-Izmir, Tiirkiye to discuss the fundamentals and applications of microscale heat transfer in biological and microelectromechanical systems. During the institute, the most recent state-of-the-art developments have been presented in considerable depth by eminent researchers in the field. This current volume, edited by Kaka et al. [19] brings together the important contributions from the institute as a permanent reference for the use of researchers in the field. 

Kakag, S., Vasiliev, L.L., Bayazitoglu, Y. and Yener, Y., (eds.). Microscale Heat Transfer - Fundamentals and Applications, 2005, Kluwer, The Netherlands. Kavehpour, H.P., Faghri, M. and Asako, Y., Effects of Compressibility and Rarefaction on Gaseous Flows in Microchannels, Numerical Heat Transfer, 1997, Part A, 32, 677-696. 

Microscale heat transfer has attracted researchers in the last decade, particularly due to developments and current needs in the small-scale electronics, aerospace, and bioengineering industries. Although some of the fundamental differences between micro and macro heat transfer phenomenon have been identified, there still is a need for further experimental, analjdical and numerical studies to clarify the points that are not yet understood, such as the effect of axial conduction, friction factors, compressibility effects, critical Reynolds number, and accommodation coefScients less then unity. 

Bayazitoglu, Y., Tunc, G., Wilson, K., and Tjahjono, I., (2005) Convective Heat Transfer for Single-Phase Gases in MicroChannel Slip Flow Analytical Solutions, presented at NATO Advanced Study Institute, Microscale Heat Transfer - Fundamentals and Applications in Biological and Microelectromechanical Systems, July 18-30, Altin Yunus - Qe me, Izmir, Turkey. 

The second microscale heat transfer issue considered in this paper deals with short time scales and their influence on the dimensions required for good heat transfer. Many cryocoolers use oscillating flows and pressures with frequencies as high as about 70 Hz. Heat flow at such high frequencies can penetrate a medium only short distances, known as the thermal penetration depth temperature amplitude of a thermal wave decays as it travels within a medium. The distance at which the amplitude is 1/e of that at the surface is the thermal penetration depth, which is given by... 

We present here a few examples of eryocooler applications to show where microscale heat transfer issues at low temperatures may be of some concern. The overall size of the eryocooler usually has little bearing on whether microscale heat transfer issues are involved. It is the hydraulic diameter that is important in determining microscale effects. Small hydraulic diameters are required for very effeetive heat exehangers, particularly for those used in high frequency regenerative cryocoolers. For... 

Bayazitoglu, Y., and Kakac, S., (2005) Flow Regimes in MicroChannel Single-Phase Gaseous Fluid Flow, Microscale Heat Transfer-Fundamentals and Applications, S. Kakae (ed.), Kluwer Academie Publishers, Dordrecht (This publication). 

Bayazitoglu, Y., and Tunc, G., (2002) Extended Slip Boundary Conditions for Microscale Heat Transfer,/4iT4 Journal of Thermophysics andHeat Transfer. Vol. 16. no 3. pp. 472-475. 

MICROSCALE HEAT TRANSFER UTILIZING MICROSCALE AND NANOSCALE PHENOMENA... 

Yener, Y., Kaka9, S., and Avelino, M. R. (2005) Single-Phase Convective Heat Trmsfer in Microchannels — The State-of-the-Art Review, NATO Advanced Study Institute on Microscale Heat Transfer, Cesme, Tiukey, July 18-30. 

In order to effectively analyze the microscale heat fransfer mechmisms and to accurately model the ulfra-short pulse heating of materials, it is necess y to understand energy absorption, fransport, and storage phenomena in detail. The primary laser-sohd interaction process is the excitation of elections from their equihbriiun states to some excited states by absorption of photons. Dephasing processes take place in a very short time of about s. The occupation of these... 

The self-consistent theoretical models based on the Boltzmann transport theory are used to characterize the microscale heat transfer mechanism by explaining mutual interactions among lattice temperature, and number density and temperature of carriers [12]. Especially, a new parameter related with non-equilibrium durability is introduced and its characteristics for various laser pulses and fluences are discussed. This study also investigates the temporal characteristics of carrier temperature distribution, such as the one- and two-peak structures, according to laser pulses and fluences, and establishes a regime criterion between one-peak and two-peak sttuctures for picosecond laser pulses. 

The influence of laser fluence and pulse duration time on microscale heat tiansfer mechanisms are investigated by using one-dimensional said transient equations of eerier and lattice temperatures. The scale difference between energy relaxation and laser pulse duration times results in file fiiermal non-equilibriimi state fiiat can be controlled by laser fluence as well as pulse dmation time. In the case fiiat a few picosecond pulse laser is irradiated over file semiconductor surface with relatively hi fluence, a two-peak structme in file carrier temperature variation can be observed. As pulse dmation increases, file m imiun eerier temperature and file number density decrease, whereas file lattice temperature is nearly of constant values. Meanwhile, the two-peak structme due to Auger heating disappears and converts into the one-peak stinctme as file laser fluence decreases. 

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