Two-phase annular flow, which is the concurrent flow of a vapor core surrounded by a thin liquid film in a pipe, is commonly found in heat exchangers and other systems where boiling happens. The thin film of evaporating liquid at the wall ensures good heat transfer between the wall and the fluid. However, beyond a certain critical heat flux (CHF) at the wall, the liquid film may dry out. In the absence of the liquid film, the heat transfer coefficient drops and the temperature of the wall exposed to vapor flow increases dramatically, which may lead to failure of the equipment.

The paper is demonstrating the use of thermoreflectance as a method for measuring wall temperature fluctuations in two-phase annular flow. Thermoreflectance relies on the change with temperature of the index of refraction of the fluid in contact with the wall. Thermoreflectance has been used in the past to measure the temperature of a substrate in contact with evaporating droplets. It is well suited for measurements in transient two-phase annular flow since it is non-intrusive, with a good resolution both in time and space and it allows for other optical measurements (e.g. film thickness, high-speed video) to be performed simultaneously.


Thermoreflectance Wall Temperature Measurement in Annular Two-Phase Flow

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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