Temperature and velocity field measurements of pool boiling using two-colour laser-induced fluorescence, infrared thermometry and particle image velocimetry
We study nucleate pool boiling in water at saturation temperature and ambient pressure under low heat fluxes. A combination of high-speed and spatially-resolved diagnostic tools are developed and applied to provide detailed insight into the flow and heat transfer mechanisms during bubble life cycle. Two fluorescent dyes with non-overlapping spectra are seeded into the water and are excited by a Nd:YLF laser sheet at 527 nm. A two-colour laser-induced fluorescence method is employed to individually track the fluorescence of each dye by connecting two cameras, equipped with separate optical filters, to a beamsplitter and a lens. Tracer particles are also introduced in the water to perform simultaneous particle image velocimetry measurements. Finally, synchronised high-speed infrared thermometry is conducted to acquire the surface temperature field over the heater. The links between the interfacial/bubble dynamics, flow and heat transfer are investigated. Superheated liquid from the thermal boundary layer adjacent to the heater is displaced upwards, due to the growth and departure of the bubbles. Two counteracting vortices form on each side of the bubbles during their departure and rise, which contribute to the scavenging and mixing of the bulk water, resulting in a trail of superheated liquid below them
