Enhanced microscale heat transfer in macro geometries : effect of flow field

• Main Author: Siew, Dennis Weng Kin
• Other Authors: Ooi Kim Tiow
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/60367
• Institution: Nanyang Technological University

With technology getting more advance, there has been a strong demand for new cooling methods to remove the heat dissipated particularly from the electrical components. It is expected that in the future, these electrical components will be able to generate over 1000 of heat flux, and conventional cooling techniques cannot be used for cooling. The most actively researched cooling techniques is the microchannel heat transfer. It was first applied by Tuckerman and Pease in 1981 who cooled a large-scale electronic circuits using forced convection of water flowing through microchannels. Since then, there have been numerous researches conducted on heat transfer in microchannels. However, complicated and costly manufacturing procedures are usually required when fabricating microchannels. Therefore, this research aims to the study enhanced microscale heat transfer on macro geometries by applying conventional manufacturing methods to create the microchannels. In this project, an insert with a slightly smaller diameter, which is 19.4 mm, was introduced into the flow channel, which is 19.4 mm, to form an annular micro flow channel. Inserts of different surface profiles were exchanged in the test rig to investigate various forms of heat transfer augmentation in the microchannel. Experimental investigation and numerical analysis were carried out for Reynolds numbers in between 1000 to 5500 with constant heat rates of 200 and 500 W. The results concluded that the design with circular grooves attained the highest heat transfer coefficient of about 71.7 kW/m2·K in the flow channel, which is about 43.5% higher than the smooth flow channel. Besides, numerical studies on other designs also revealed that the designs with forward and backward sloping grooves are able to achieve comparably good heat transfer augmentation in the range of 10.6 to 33.1% higher. In conclusion, these results showed achieving enhanced microscale heat transfer in macro geometries is highly possible using conventional manufacturing methods.