The current trend in microelectronics is to manufacture devices with increased computational powers and reduced size. These devices with increased power densities are consequently subject to extreme thermal loads. Thermal management of these power loads is extremely challenging. The presence of the hotspots can make this challenge even more difficult. Jet impingement cooling is one of the top candidates for removing such extreme heat fluxes in microelectronics. Jet impingement cooling can achieve heat transfer coefficients (HTCs) due to its normal incident flow-field and ability to thin the local thermal boundary layer in the stagnation region. This dissertation presents the hotspot cooling performance for a confined jet impingement cooling configuration. This dissertation is divided into two parts. The first part presents the experimental data attained for single-phase water jet impingement cooling. Also investigated is the spatial dependence of the HTC relative to the offset between the jet/wall stagnation point and the center of the local hotspot. A theoretical model to predict the HTC as a function of jet-to-hotspot offset ratio and heating frequency is also derived. The second part presents hotspot cooling performance for the two-phase confined jet cooling performance. Electrically non-conductive fluids such as Novec 7100, Novec 7200, FC 72, and Ethanol were used as coolants for this part of the study. This study investigates the nucleate boiling regime as a function of the Reynolds number/Jet Velocity for these fluids. Additionally, this dissertation also presents the nucleate boiling regime as a function of the distance between the hotspot center and the jet stagnation point. Finally, a stagnation zone CHF prediction model is derived. Findings from this research will help thermal control engineers write active cooling algorithms to maintain the desired temperature at minimal pumping cost. This research will also help thermal designers to select appropriate coolants and design the device.


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Graduation Date





Putnam, Shawn


Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science


Mechanical and Aerospace Engineering

Degree Program

Mechanical Engineering


CFE0009292; DP0026896





Release Date

June 2023

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Open Access)