Understanding interfacial behaviour during boiling of nitrogen from liquid-liquid contact plane

• Published in: International journal of heat and mass transfer 2021-02, Vol.165, p.120661, Article 120661
• Main Authors: Kumar, Rupak, Rohilla, Lokesh, Das, Arup Kumar
• Format: Article
• Language: English
• Subjects: Behavior; Bubbling; Cryogenic boiling; Diameters; Film boiling; Interface stability; Liquid nitrogen; liquid-liquid interface; Low temperature; Nitrogen; Optical measurement; Stability criteria; Taylor instability; Vapor clouds; Vaporization
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2020.120661

•Interfacial behaviour during film boiling at liquid-liquid interface has been observed.•Measured heat flux has been found to be following theoretical film boiling correlations.•Regime identification of bubbling behaviour at LN2 under Rayleigh-Taylor instabilities has been conceptualized.•Residence time and opacity of dense vapor plume have been quantified.•Subsurface boiling has been portrayed at liquid-liquid interface by varying base fluid density. In this paper, a combined photographic and thermal study of interfacial behaviour during boiling of liquid Nitrogen (LN2) over the water surface is reported. As a phenomenon, film boiling behavior is observed and the same is compared with the available correlations in literature. Apart from boiling, during experiments of LN2 drop over water of low temperature, icing has been observed which changes the overall interfacial activities. Rayleigh-Taylor instability (RTI) based criterion has been used to differentiate between regimes which are no bubbling, moderate and vigorous bubbling, based on the release of nitrogen vapor (N2) from the entrapped liquid layers. No bubbling behavior is observed when the equivalent diameter of the LN2 drop is lesser than the critical wavelength and the generated vapor flux during boiling is sufficient to levitate the drop. The N2 vapor cloud generated over the drop is also characterized by optical measurement to relate opacity and temperature. At the end, the phenomenon of sub-surface boiling is also reported through experiments of LN2 boiling over base fluids other than water.