טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMischan Yaron
SubjectNumerical and Experimental Investigation of Micro-Channels
Heat Sink for Cooling Electronic Devices
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Emeritus Gad Hetsroni (Deceased)


Abstract

Electronic components and silicon chips are conventionally cooled today by natural or forced convection of air flowing over the device, normally, enhanced by fins attached to it. In order to deal with the accelerated increase of generated heat, the design and performance of the cooling mechanism will need to improve dramatically relative to the current heat dissipation systems. The use of micro-channel heat sinks (with hydraulic channel diameters in the range of 10-500m) is a promising alternative which can provide very high heat removal rates and may also be integrated directly into the heat-dissipating substrates.

The present numerical and experimental investigations were focused on understanding the fundamentals of micro-channel flow and heat transfer mechanism and to explore the validity of classical correlations based on large size channels for predicting the hydrodynamic and thermal behavior in laminar single-phase flow.

Numerical analysis was performed to optimize the main geometric parameters of the test section including the inlet and outlet manifolds. A major goal was to obtain a uniform flow distribution among the parallel channels to enhance heat transfer and eliminate hot spots. As a result of the simulations, a test module micro-machined aluminum based heat sink was developed and manufactured for the experimental investigation. Calculations and experiments were performed with clear water flowing in parallel rectangular micro-channels of hydraulic diameter 440m, with heat fluxes up to 150 W/cm2 and Reynolds number in the range of 35-600. A comparison between predictions of the conventional theory and experimental data on the friction factor revealed satisfactory agreement taking into account the entrance effects, developing flow and the channel surface (relative high roughness) conditions. New infrared Technique for measuring the Temperature distribution of the working fluid along the heated surface was devised. It was shown that the temperature of the heated wall did not change linearly along the channel. This deviation from the behavior expected for conventional channels is due to axial thermal conduction through the channel walls.