Abstract
To overcome the problem of abnormally large bubbles and the large reduction of heat flux under low gravity, the computational model of magnetic nanofluid (MNF) boiling flow was used to systematically study the thermodynamic characteristics of an MNF-saturated film boiling with and without the magnetic field. This study found that in the absence of a magnetic field, the decrease of the gravity level makes the bubble size increase and the bubble departure time increase, and the lower the gravity level, the worse the boiling heat transfer. However, after applying the magnetic field, bubble size decreases significantly and the bubble departure time is shortened. As the magnetic field intensity increases, the difference in bubble size and heat transfer characteristics between different gravity levels becomes smaller and smaller, which shows that for the boiling flow of MNF under low gravity levels, applying a magnetic field can effectively avoid the appearance of abnormally large bubbles, enhance heat transfer, and improve the safety of related heat transfer equipment.
Highlights
Boiling and condensation are considered to be the most effective means of heat transfer in many types of technical equipment
Aiming at a problem that is rarely reported in the study of the phase-interface evolution of magnetic nanofluid (MNF) boiling heat transfer, the basic computational model of two-phase boiling flow should be solved, and the coupled magnetic field computational model and magnetic field force model should be developed on the basis of this basic computational model
It is speculated that the application of the magnetic field may solve the problems of large bubbles escaping and the heat flux decreasing in the boiling process under reduced gravity or even microgravity
Summary
Boiling and condensation are considered to be the most effective means of heat transfer in many types of technical equipment. Experimental and numerical methods have been used to study boiling heat transfer under reduced gravity levels. In our previous study [16,17], a numerical simulation for MNF film boiling was developed to investigate the heat transfer performance and dynamic characteristics by applying a uniform and non-uniform magnetic field. The heat transfer characteristics and thermodynamic characteristics of the phase interface of an MNF-saturated film boiling under different levels of reduced gravity will be further studied in detail by exploring the multiple physical-field couplings between different gravity fields and the velocity field, pressure field, temperature field, phase field, and magnetic field, further revealing the enhancement mechanism of the MNF’s boiling heat transfer by applying the magnetic field under the influence of different gravitational fields
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