Saturated film boiling at various gravity levels under the influence of electrohydrodynamic forces

Abstract

The present work is focused on the analyses of the bubble growth and heat transfer characteristics in saturated film boiling at various levels of gravity. In addition to this, the occurrence of self-similarity in interface structures during the bubble growth is examined. The phenomenon of bubble growth is strongly influenced by the buoyant forces due to gravity and its dominant effect is found to be replaced by the electrohydrodynamic forces in reduced gravity conditions. The decrease in gravitational acceleration results in increasing the characteristic wavelength and time scale. The bubble volume and maximum height before pinch-off thus increase enormously as the gravity value is reduced. The bubble pinch-off velocity is found to be decreased significantly in the case of reduced gravity condition. Heat transfer rate deteriorates in reduced gravity conditions which can be recovered by the externally imposed electric field. The dominance of electric field on the heat transfer rate is found to be more in reduced gravity condition. However, as the value of imposed electric field is enhanced, the difference in the effect of increasing heat flux tends to reduce.

Boiling heat transfer modelling: A review and future prospectus

“…Another novel technical utilization of boiling is related to the water-cooled fusion reactors in which the cooling components are exposed to plasma and, therefore, to one-sided heating with extremely high heat flux rates (e. g. in ITER * , that is just an experimental device, heat loads as high as 5 MW/m 2 are expected according to [22]). Further, the understanding of new aspects of boiling phenomena in conditions of low gravity is indispensable for the design of cooling systems in powerful electronic packages for space applications [23]. Finally, we would like to emphasise that extensive boiling research will also have a positive impact on the scientific efforts directed to designing of techniques for boiling heat transfer enhancement and CHF delay as it will provide a basis for the assessment of the existing methods (e. g. use of micro/nano-structured surfaces, increase of surface wettability, addition of nanoparticles) and establish guidelines for the development of conceptually new ones.…”

“…In old civilisations the boiling was used for sophisticated technical applications, THERMAL SCIENCE: Year 2019, Vol. 23,No. 1, too.…”

Application of a Magnetic Field in Saturated Film Boiling of a Magnetic Nanofluid (MNF) under Reduced Gravity

“…Numerical simulations are easier to implement and make it easier to obtain more details than experimental methods, and thus help to better understand the heat transfer mechanism under reduced gravity. In the last few decades, great efforts have been made to improve the numerical simulation methods for two-phase flow and phase change, and many scholars [8][9][10] have used these methods to study boiling performance under reduced gravity.…”

Numerical investigation on bubble dynamics during pool nucleate boiling in presence of a non-uniform electric field by LBM

“…Until now, some scholars numerically investigated different EHD phenomena, such as the deformation of a droplet in a uniform electric field and a rising bubble under an external electric field [7][8][9]. These numerical investigations laid a foundation for studying the influence of EHD on bubble dynamics during nucleate boiling or film boiling, which has been studied by many scholars using various numerical methods [10][11][12][13]. Welch and Biswas [10] employed level-set method to simulate the film boiling under a uniform electric field, and they found that wall temperature decreased with an increase in electric field intensity at a given heat flux condition.…”

“…Welch and Biswas [10] employed level-set method to simulate the film boiling under a uniform electric field, and they found that wall temperature decreased with an increase in electric field intensity at a given heat flux condition. Tomar et al [11] and Pandey et al [12] simulated the effect of a uniform electric field on film boiling under different gravitational accelerations by CLSVOF method, and these authors found that increasing electric field intensity could increase both the averaged Nusselt number and the bubble release frequency. In addition, the influence of the electric field on film boiling heat transfer would be greater with a decrease in gravitational acceleration.…”