We experimentally investigate the vaporization of water droplets immersed in a hot oil film, with moderate temperaturedifferentials of 30–50 °C. In this regime, only a fraction of the water droplet vaporizes, but results in a symmetric vertical jet of oil. We provide detailed high-speed imaging of the physical process and quantitatively describe the vapor bubble growth, jet formation, jet speed and satellite droplets resulting from the jet break-up. The principal findings are that the jet speeds (vjet∼O(1) m/s) are inversely correlated to the oil film thickness (δ∼O(1) mm), whilst the surface tension-driven break-up results in primary satellite droplets whose normalized diameters also scale inversely with film thickness. Lastly, we provide observations of a water ‘peeling’ mechanism which occurs inside the vapor bubble, leading to a re-entrant jet that ultimately causes a secondary vaporization event.
|Journal||Experimental Thermal and Fluid Science|
|State||Published - Dec 2019|
- Liquid jets
- Water peeling
- surface tension