Ferro-advection aided evaporation kinetics of ferrofluid droplets in magnetic field ambience

被引:20
|
作者
Chattopadhyay, Ankur [1 ]
Dwivedi, Raghvendra Kumar [1 ]
Harikrishnan, A. R. [2 ]
Dhar, Purbarun [3 ]
机构
[1] Indian Inst Technol Ropar, Dept Mech Engn, Rupnagar 140001, Punjab, India
[2] Birla Inst Technol & Sci Pilani, Dept Mech Engn, Pilani 333031, Rajasthan, India
[3] Indian Inst Technol Kharagpur, Dept Mech Engn, Kharagpur 721302, W Bengal, India
关键词
SURFACE-TENSION; PENDANT; COMBUSTION; SHAPES; FLUID; NANOPARTICLES; VAPORIZATION; WETTABILITY; INSTABILITY; ADSORPTION;
D O I
10.1063/5.0018815
中图分类号
O3 [力学];
学科分类号
08 ; 0801 ;
摘要
The present article discusses the physics and mechanics of evaporation of pendant, aqueous ferrofluid droplets, and modulation of the same by an external magnetic field. We show experimentally and by mathematical analysis that the presence of a horizontal magnetic field augments the evaporation rates of pendant ferrofluid droplets. First, we tackle the question of improved evaporation of the colloidal droplets compared to water and propose physical mechanisms to explain the same. Experiments show that the changes in evaporation rates aided by the magnetic field cannot be explained on the basis of changes in surface tension or based on classical diffusion driven evaporation models. Probing via particle image velocimetry shows that the internal advection kinetics of such droplets plays a direct role toward the augmented evaporation rates by modulating the associated Stefan flow. Infrared thermography reveals changes in thermal gradients within the droplet and evaluating the dynamic surface tension reveals the presence of solutal gradients within the droplet, both brought about by the external field. Based on the premise, a scaling analysis of the internal magneto-thermal and magneto-solutal ferroadvection behavior is presented. The model incorporates the role of the governing Hartmann number, the magneto-thermal Prandtl number, and the magneto-solutal Schmidt number. The analysis and stability maps reveal that the magneto-solutal ferroadvection is the more dominant mechanism, and the model is able to predict the internal advection velocities with accuracy. Furthermore, another scaling model to predict the modified Stefan flow is proposed and is found to accurately predict the improved evaporation rates.
引用
收藏
页数:12
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