Date: Wednesday, April 19, 2023
Time: 9:30-10:30AM
Location: Health Science Technology Building (HST), Forum Room 101
This event features Joel Plawsky, who will talk about "Heat Pipes in Space: What Could Go Wrong?", as part of the Lehigh University Chemical and Biomolecular Engineering's Spring 2023 Colloquium Seminar Series.
Abstract
Heat pipes combine thermal conduction, liquid-vapor phase change, and in many designs, capillary flow, to transport energy efficiently between a heat source and a heat sink. They can be used for cooling microprocessors, keeping permafrost frozen, and for thermal management in spacecraft and satellites. Because a heat pipe’s fluid circulation is driven by interfacial forces, the devices operate without any moving parts, which makes them simple, light, and reliable: perfect for space exploration.
Transparent, wickless heat pipes of square cross-section were operated in the microgravity environment aboard the International Space Station. The idea was to map the liquid-vapor interface and liquid film thickness profiles within the device and thereby understand the fluid and heat transfer characteristics of its operation in microgravity. Partly due to the low thermal conductivity of the glass walls, as heat inputs were increased, Marangoni flows developed that offset the capillary return flows in the corners of the device. These offsetting flows flooded the heater end with liquid and caused liquid to also accumulate on the flat faces of the heat pipe in the form of a liquid drop. As the heat input was increased further, the drop ejected a stream of liquid out toward the heater end. This stream was a classic rip current, driven by two counterrotating vortices present in the drop. The formation of the current is a natural mechanism allowing the system to reject the increasing heat load when the normal modes of evaporation are cut off by the presence of strong Marangoni flows near the heated end of the device. In the shortest version of the heat pipe, we observed a form of slow-motion boiling, driven by vapor bubble nucleation at the heater end and strong Marangoni flows. The boiling phenomenon is only possible if the liquid film at the heater end exceeds a critical thickness.
About the Speaker
Joel L. Plawsky is currently the department head of the Howard P. Isermann Department of Chemical and Biological Engineering at Rensselaer Polytechnic Institute. He received his B.S. in Chemical Engineering from the University of Michigan and his M.S. in Chemical Engineering Practice and Sc.D. in Chemical Engineering from the Massachusetts Institute of Technology. After graduation, Joel worked on optical fiber devices for Corning Inc. in their research division before returning to academia at Rensselaer Polytechnic Institute.
Joel’s research interests are in applied transport phenomena. Most of his work has focused on thin films, with applications in the semiconductor, photonics, and thermal management industries. Joel was a NASA Faculty Fellow in 1999 and 2000 and a visiting professor of chemical engineering at Delft University of Technology in 2002. While on sabbatical in 2003 at Marshall Space Flight Center, Joel worked on Shuttle tile repair formulations following the Columbia accident and thermal management systems for aerocapture. He is a fellow of the American Institute of Chemical Engineers and the American Society of Mechanical Engineers. Joel is also the author of a textbook, Transport Phenomena Fundamentals, 4th edition, published by CRC Press. He holds 10 patents in the areas of spouted bed technology for mixing, coating, and water purification; photonic systems; thermal interface materials, and MEMS flow boiling systems for integrated circuit temperature control.
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