Abstract

Heat dissipation is vital in industries requiring predictable operating temperatures while also producing large heat fluxes. These industries include electronics and power generation. For electronics, as more devices fit on a smaller area, the heat flux increases dramatically. Pool boiling offers a solution to electronic cooling due to extremely high heat transfer with a low temperature change. Previous research has focused on coatings and precision manufacturing to create microchannels and features for boiling augmentation. However, this is limited to designs for subtractive processes. The use of additive manufacturing (AM) offers a novel way of thinking of design for boiling enhancement. 3-D boiling structures are fabricated out of aluminum using the Vader System's magnetojet printer. Three generations of geometric structures are created: a volcano-with-holes, a miniaturized volcano-with-holes, and a modular volcano-with-holes. These designs are not easily manufactured using standard techniques. As such, three-dimensional bubble dynamics are currently being explored using high speed imaging and particle image velocimetry. By printing a volcano shape with base holes, the liquid and vapor phases are physically separated in a process termed macroscale liquid-vapor pathways.

The singular volcano-with-holes chips achieved a maximum heat flux of 217.3 W/cm2 with a maximum heat transfer coefficient (HTC) of 97.2 kW/m2K (81% improvement over plain). By producing four volcanoes on a single chip, the liquid flow length inside the volcano, which acts as the entrance length, is reduced by 50% and the HTC greatly increased. The highest performing miniaturized volcano-with-holes chip reached a maximum heat flux of 223.1W/cm2 with a maximum HTC of 139.1 kW/m2K (150% improvement over plain). Additionally, the highest performing miniaturized chip was printed on top of a microchannel array. This resulted in combined enhancement from both microchannel and bubble dynamics resulting in a maximum heat flux of 228.4 W/cm2 with a HTC of 339.6 kW/m2K (533% improvement over plain). Finally, a modular structure was created to determine the individual influence of conduction and bubble dynamic augmentation on boiling enhancement. The modular designs show an 83% improvement in CHF (202.4 W/cm2) over plain copper chips and a 83% improvement in HTC(139.0 kW/m2K). This indicates boiling enhancement arises from three-dimensional control over bubble dynamics, resulting in macroscale separate liquid-vapor pathways.

Publication Date

5-2018

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Satish G. Kandlikar

Advisor/Committee Member

Michael Schrlau

Advisor/Committee Member

Denis Cormier

Campus

RIT – Main Campus

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