Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7054076 | International Journal of Heat and Mass Transfer | 2018 | 10 Pages |
Abstract
We carried out a visualization study of Departure from Nucleate Boiling (DNB) of a vertical upward flow boiling condition. In order to evaluate the effects of the convective flow condition on the DNB mechanism, we synchronized three high-speed cameras (bottom view, side view and total internal reflection view) and captured the detailed dry patch dynamics and relevant bubble behavior. A convective flow of 250â¯kg/m2â¯s and subcooled 5â¯Â°C (water) was controlled on a heating surface (10â¯mmâ¯Ãâ¯120â¯mm), which is much larger than the Rayleigh-Taylor instability wavelength (approximately 25â¯mm). As a brief result, a high heat flux near DNB (1000â¯kW/m2) produced periodic massive elongated bubbles through numerous bubble coalescence, and a thin liquid film was developed on the heater surface. Local evaporation of the thin liquid film generated a dry patch, which was observed using a total internal reflection technique. Accounting for the dry patch size and lifetime, the local overheated condition of the dry patch was discussed as an important physics of the irreversible dry patch (DNB). This study may provide a deep insight for understanding the DNB mechanism on the relatively low mass flow boiling condition.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Fluid Flow and Transfer Processes
Authors
Seol Ha Kim, In Cheol Chu, Moon Hee Choi, Dong Jin Euh,