Advances in microfabrication technology have allowed the use of microchannels in ultra compact, very efficient heat exchangers, which capitalize on the channels large surface area to volume ratio to transport high heat fluxes with small thermal resistances. One example is the cooling of microchips. However, the research into microscale flow and heat transfer phenomena conducted by various researchers provided substantial experimental data and considerable evidence that the behaviour of fluid flow and heat transfer in microchannels without phase change may be different than that which normally occurs in larger more conventional sized channels.This paper serves to perform a numerical analysis on the flow and heat transfer in manifold microchannels. A numerical model for 16 sets of parametric conditions is presented here using a CFD package, ANSYS/FLOTRAN. Pressure, temperature and velocity contour plots were obtained and analyzed. The results obtained were then compared with a derived analytical model. The predictions showed a large dependence on the flow rate. Differences in values and trends were expected as the analytical model assumed a straight channel unlike a manifold channel. Further comparisons were also made regarding the relationship between Reynolds number and the friction factor. Data were also compared with Copeland's simulation (1995) using FLUENT software and the agreement is good.

Advances in microfabrication technology have allowed the use of m.crochannels in ultra compact, very efficient heat exchangers, which capitalize on the channels large surface area to volume ratio to transport high heat fluxes with small thermal resistances. One example is the cooling of microchips. However, the research into microscale flow and heat transfer phenomena conducted by various researchers provided substantial experimental data and considerable evidence that the behaviour of fluid flow and heat transfer in microchannels without phase change may be different than that which normally occurs in larger more conventional sized channels.This paper serves to perform a numerical analysis on the flow and lieat transfer in manifold microchannels. A numerical model for 16 sets of parametric conditions was created using a CFD package, ANSYS. Pressure, temperature and velocity contour plots were obtained and analyzed. The results obtained were then compared with a derived analytical model. The predictions showed a large dependence on the flow rate. Differences in values and trends were expected as the analytical model assumed a straight channel unlike a manifold channel. Further comparisons were also made regarding th12 relationship between Reynolds number and the friction factor. Data were also compared with the research of another author using FLUENT software. INTROIDUCTIONThe design of high-speed, high-power integrated circuits anti systems is often constrained by thermal considerations. There is a contradictory requirement for high rates of heat dissipation with low allowable temperature rise. Heating rates on the order of 10 W/cm2 are commonly produced and the allowable temperature rise is usually limited to approximately 80°C above a 2OoC ambient. In this decade however, the allowable temperature rise is expected to decrease somewhat, and the heat dissipation rate is expected to be in the range of 200 to 1000W/cm2. Hence, innovative cooling techniques will be required to llffdl these requirements and one such method is the use of forced convection heat spreaders called microchannel heat sinks. A microchannel heat sink is a structure with numerous channels and fins mmged parallel to one another and very close to the heated surface. The dissipated heat passes through the heat sink by conduction and to the coolant by forced convection.The coolant is usually a liquid rather than a gas and the flow is usually single phase rather than two-phase. With the 0-7803-51 41 -W98 $1 0.00 0 1 998 IEEE advancement of micromachining techniques, constructing such small but highly efficient micro heat exchangers is feasible.The concept of a microchannel heat sink was first introduced in 1981 by Tuckerman and Pease at Stanford University [l]. Microchannel array has been found effective for cooling electronic devices. The current work intends to carry out a numerical simulation of the flow and heat transfer in a microchannel array with unidirectional flow condition in order to obtain the flow field and the temperature distributio...

This paper presents a computer model with the use of a finite-volume scheme on the liquid flow and heat transfer in microchannels, with streaming potential as the driving force. The concept of electric double layer (EDL) was introduced to explain the microscale deviation. Interfacial electrokinetic phenomena such as the EDL play important roles in various transport processes in microchannels. Conventional theories of fluid mechanics and heat transfer cannot explain these phenomena observed in microchannels. The presence of the EDL reduces the liquid velocity within the microchannel, which affects the heat transfer mechanism in the pressure-driven microchannels. In this paper, a source term in the form of the electrical body force was included in the governing momentum equations for microscale computation with the effects of the heat transfer through the channel wall. The numerical parametric studies performed allowed the conclusion that the flow and heat transfer characteristics in microchannels depend on the bulk ionic concentration, the Zeta potential and the aspect ratio of the channel, which is the reflection of the EDL effects. The existing of the EDL is more significant as aspect ratios decrease. Also, the friction coefficient increases as the ionic concentration of the aqueous KCL solution decreases and the Zeta potential of the system increases. However, one should be aware that the ionic concentration of 10 −8 M is unlikely in reality.

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