The following study investigates the behavior of bubbles created by air injection under a tapered microgap. It is a continuation of previous work from the Thermal Analysis and Microfluidics Lab at RIT which showed that placing a tapered gap manifold over a heated surface in a pool boiling setup could direct the flow of vapor created by two-phase heat transfer and create a pumping effect to increase its heat transfer performance. This study isolates this phenomenon and examines exactly how bubble motion affects liquid throughput. The results of this study provide insight into the specific parameters which induce this effect such as taper angle, flow rate of air, and manifold gap height. An experimental setup has been fabricated which mimics the flow of vapor created by pool boiling on a heated surface. It consists of a volume of water, an orifice through which air is supplied, a polysulfone taper, a peristaltic pump, and a high speed camera to record motion. Videos are saved and analyzed in a tracking software to provide position, velocity, and acceleration data. This data is used to compare taper configurations and evaluate performance. Four different flow patterns were observed during the passage of air through the microgap: “bubble squeezing”, ”bubble sticking”, ”no squeezing”, and “bubble slingshot. The installation of side curtains on the taper restricted flow to the inlet and outlet and prevented fluid from escaping from the sides. Taper angle and inlet area were seen to be the most influential parameters in the flow pattern outcome for the bubble. The most desirable flow patterns are “bubble squeezing” and “bubble slingshot” as they provide higher interface velocities indicative of increased liquid throughput. This is expected to improve the heat transfer during boiling in this geometry.

Library of Congress Subject Headings

Heat--Transmission--Research; Bubbles--Dynamics; Ebullition

Publication Date


Document Type


Student Type


Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)


Satish G. Kandlikar

Advisor/Committee Member

Rob Stevens

Advisor/Committee Member

Hany Ghoneim


RIT – Main Campus

Plan Codes