**Micro-Channels and Compact Heat Exchangers**

186 Heat Exchangers – Basics Design Applications

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**8** 

*Iran* 

**Microchannel Simulation** 

*Sharif University of Technology* 

Mohammad Hassan Saidi, Omid Asgari and Hadis Hemati

In the current state of fast developing electronic equipment, having high speeds and at the same time high heat generation rates, researchers are trying to find an effective microcooling method. The main problem in the cooling of microdevices is their high heat generation rate in a limited space. In this way, much research has been conducted on the analysis of different novel microcooling methods such as microheat pipes, microjet impingements, microcapillary pumped loops, microelectrohydrodynamic coolers, and microchannel heat sinks. Among the different microcooling devices the microchannel heat sink has been of special consideration due to its capabilities such as high capacity of heat removal. In principle, microchannels can be machined at the back of a substrate of electronic chips and, therefore, can reduce the internal (contact) thermal resistance of the heat sink practically to zero. The cooling rates in such microchannel heat exchangers should increase significantly due to a decrease in the convective resistance to heat transport caused by a drastic reduction

The overall excellent potential capacity of such a heat sink for heat dissipation is based on the large heat transfer surface-to-volume ratio of the microchannel heat exchangers. The use of microchannel heat sink was first introduced by Tuckerman and Pease in 1981 [1]. Their research was based on an experiment where they showed that high heat rates of 790 *W/cm2*

Currently, research in the field of microchannels is going on in three aspects of experimental methods [2,3,4], numerical methods [5,6,7,8], and analytical methods [9,10,11,12]. It is well known that the cross-sectional shape of a channel can have significant affect on the fluid flow and heat transfer characteristics in microchannels. Peng and Peterson [13] performed experimental investigations of the pressure drop and convective heat transfer for water flowing in rectangular microchannels, and found that the cross-sectional aspect ratio had significant influence on the flow friction and convective heat transfer in both laminar and turbulent flows. Kawano et al. [14] provided experimental data on the friction and heat transfer in rectangular, silicon based microchannel heat sinks, and more recently Wu and Cheng [15,16] conducted a series of experiments to measure the friction factor and convective heat transfer in smooth silicon microchannels of trapezoidal cross-section. The experimental methods has its own values and the new developments in the micromachining techniques help the researchers to perform precise experiments, but because of its high cost

**1. Introduction** 

in the thickness of thermal boundary layers.

could be removed by microchannel heat sinks.

it fails to be commonly applied.
