Master of Science, The Ohio State University, 1989, Food, Agricultural, and Biological Engineering

Heat transfer coefficients (h) between fluids and particles were determined for three situations: the first two involving natural convection of a mushroom-shaped particle immersed in Newtonian and non-Newtonian liquids, and the third involving continuous flow of a sphere within liquid in a tube. For natural convection studies, h was much higher for heating than for cooling, and decreased with time as equilibration occurred. For the continuous flow studies, h was found to increase with flow rate.

Committee: Sudhir Sastry (Advisor) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2013, EECS - Electrical Engineering

This work demonstrates an innovative microfabricated air cooling technology that employs an electrohydrodynamic (EHD) corona discharge or ionic wind pump that has the potential to meet industry requirements as a next generation solution for thermal management applications. A single ionic wind pump element consists of two parallel collecting electrodes between which a single emitting tip is positioned. A grid structure on the collector electrodes enhances the overall heat transfer coefficient and facilitates an IC compatible and batch process. The main purpose of the work presented here is thus to investigate whether an optimized ionic wind pump employed in an array configuration might exhibit performance comparable to a conventional CPU fan. The manufacturing procedure developed for the device uses a glass wafer, a single mask-based photolithography process, a low cost copper-based electroplating method, and explores the effect of employing a palladium coating on the device. Various design configurations and optimization processes were explored and modeled computationally to investigate their influence on the cooling phenomenon. The optimized single element device provides a convection heat transfer coefficient of up to 3200 W/m2-K and a COP of up to 46.7 (a maximum COP of 51.5 exhibited by the 6-element array) exhibiting an overall area of 5.35 mm x 3.61 mm, an emitter-to-collector gap of 500 ¿¿m, and an emitter radius curvature of 12.5 ¿¿m. When compared with other ionic wind pumps, the device developed for this work is superior in terms of heat transfer coefficient and COP. However, the overall performance of the array does not compare favorably to a conventional CPU fan except in terms of COP. Additionally, the lifetime experiments conducted demonstrate that additional work may be required to extend the operation of the device, and some form of non-porous coating may be required to protect the underlying copper material. Nonetheless, the device described herein (open full item for complete abstract)

Committee: Alexis Abramson PhD (Advisor); Norman Tien PhD (Committee Member); Christian Zorman PhD (Committee Member); Jaikrishnan Kadambi PhD (Committee Member) Subjects: Design; Electrical Engineering; Electromagnetics; Energy; Engineering; Experiments; Fluid Dynamics; Materials Science; Mechanical Engineering; Physics; Plasma Physics; Solid State Physics; Systems Design; Theoretical Physics