Can Water Remain a Liquid above 100C at Normal Atmospheric Presssure?
The quick answer is "no". Right? After all, we know that water reaches about 100C (212) from our experience with boiling water in a teapot. But the more insightful answer is "yes": water can remain a liquid up to 300C (or thereabouts). This capacity of a liquid to be heated well above its normal boiling point – to "superheat" it – forms the basis of microscale bubble pump technologies for moving fluids on the microscale, the most prominent example being the thermal ink jet printer.
This project will concern using a sophisticated but easy-to-use experimental design that we developed for heating liquids to temperatures well above their normal boiling points. The heaters are immersed in a liquid (e.g., water or an organic liquid) and heated very rapidly (upwards of a billion degrees per second) until a bubble forms. We capture the instant of bubble formation by making the microscale thin film heater part of a "wheatstone bridge" (a schematic is shown below) with suitable electrical filtering to produce a clear response signal.
Solid state metal films used in pulse heating applications are typically fabricated onto solid substrates. The configuration to be used in this study is a novel structure fabricated across an air gap (that provides an insulating effect to heat flow), shown in the schematic above. Significantly less energy is required to nucleate bubbles compared to configurations with a solid in place of the air (the typical configuration).
For this project, some familiarity with operating digital oscilloscopes, pulse generators and Labview would be helpful, though not necessary.
Recent related publication:
Cavicchi, R.E. and Avedisian, C.T. "Bubble Nucleation, Growth and Surface Temperature Oscillations on a Rapidly Heated Microscale Surface immersed in a Bulk Subcooled but Locally Superheated Liquid under Partial Vacuum," Int. J. Heat Mass Transf., 54, 5612-5622 (2011).
For more information please contact Prof. C.T. Avedisian
cta2@cornell.edu mailto:cta2@cornell.edu
607-255-5105