Inversion of flow and heat transfer of the paramagnetic fluid in a differentially heated cube

• Published in: International journal of heat and mass transfer Vol. 151; p. 119407
• Main Authors: Kenjereš, S., Fornalik-Wajs, E., Wrobel, W., Szmyd, J.S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2020; Elsevier BV
• Subjects: Computer simulation; Conduction heating; Heat transfer; Heat transfer control; Integrals; Magnetic fields; Magnetization force; Nonuniform magnetic fields; Numerical analysis; Paramagnetic fluid; Thermal stratification; Thermomagnetic convection; Magnetization force; Paramagnetic fluid; Thermomagnetic convection; Heat transfer control
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2020.119407

•We performed combined experimental and numerical studies of flow and heat transfer reorganization of a paramagnetic fluid by imposed magnetization force.•We consider two different heating scenarios regarding an initial thermal stratification: unstable (heated from the bottom) and stable (heated from the top) - both subjected to the same magnetic field.•A good agreement between measurements and numerical simulations in predicting the integral heat transfer is obtained over a range of imposed magnetic field.•It is demonstrated that a significant heat transfer enhancements were obtained in comparison with the neutral (no magnetic field) cases. The present study addresses the detailed numerical analysis of the flow and heat transfer of a paramagnetic fluid inside a differentially heated cubical box and subjected to a strong non-uniform magnetic field. Two different heating scenarios are considered regarding an initial thermal stratification: unstable (heated from the bottom) and stable (heated from the top), both subjected to the same magnetic field. For a fixed value of the thermal Rayleigh number (Ra=1.4×105) integral heat transfer is measured over a range of imposed magnetic fields, 0 ≤ |b0|max ≤ 10 T. To obtain detailed insights into local wall-heat transfer and its dependency on the flow patterns generated, numerical simulations of the experimental setup are performed. A relatively good agreement between experiments and numerical simulations is obtained in predicting the integral heat transfer (with an averaged ΔNu¯<7% over the entire range of working parameters for both heating configurations). It is demonstrated that a strong convective motion can be generated under the influence of the magnetization force even for the heated-from-above situation that initially was in the pure conduction state. This magnetically assisted (heated from the bottom) and magnetically inverted (heated from the top) Rayleigh-Bénard convection produced up to 5 and 15 times more efficient heat transfer compared to the initial neutral situation, respectively.