טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSmith Dafna
SubjectHeat Transfer in Microchannels and Pool-Boiling in the
Presence of Degraded Surfactants
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Emeritus Gad Hetsroni (Deceased)
Full Thesis textFull thesis text - English Version


Abstract

Thermoelectric cooling, direct immersion pool boiling, liquid jet spray cooling, heat pipes, and forced convective boiling in microchannels are methods that are under experimental studies and some are already offered for commercial use in order to remove heat generated by electronic devices.Research show that surfactants reduce drag in turbulent single-phase flows and enhance boiling mechanism in pool boiling. It is also well known that surfactants have a certain life span and after some time or extreme conditions they are degraded.The current research focuses on single-phase and two-phase forced flow convection of water and APG degraded surfactant solutions in microchannels. In order to study the phenomena, a micro-channel module has been assembled and connected to a fluid loop and a visualization system. The silicon module was designed to simulate an electronic chip. The source of heat was a mμ100 aluminum resistor deposited on the bottom of a mμ500 chip of silicon. On the top of the chip 21 parallel evenly spaced triangular micro-channels of mμ261 wide and mμ184 deep were etched, and covered by Pyrex glass to allow flow visualization. The flow visualization was done through a microscope and a high-speed camera. A thermal map of the resistor was acquired using a CCD Infrared Camera. Inlet and outlet temperature and pressure were measured and recorded using a data acquisition system and software. To support the study, a pool boiling system was assembled. It was shown that degraded solutions do not enhance heat transfer in micro-channels and the pool boiling curve varied from previous studies.