Effective in-field thermal conductivity of ferrofluids

Abstract

A structural model to predict in-field thermal conductivity of ferrofluids is proposed in this study and is validated by the experimental data from the literature. The model is able to capture the aggregation development of the magnetic particles with increasing magnetic field strength. Introducing a compression function that can be found empirically, the model can accurately predict the thermal conductivity, especially the plateauing at low and high magnetic fields.

Impact of the Magnetic Field on the Performance of Heat Pipes Driven by a Photovoltaic–Thermal Panel with Nanofluids

“…The solar photovoltaic panel is constructed of various modules and each module consists of arrays and cells. The dynamic current output can be obtained as follows [19][20][21][22][23]: In this study, various water-based nanofluid flow rates were considered and analyzed in different conditions of magnetic field forces to assess their impact on the performance of the PV-thermal heat pipe hybrid system. "This hybrid system was intended for power generation by the PV solar panels and using the thermal excess heat transferred and heat pipes to produce hot water for domestic and/or industrial use.…”

“…The solar photovoltaic panel is constructed of various modules and each module consists of arrays and cells. The dynamic current output can be obtained as follows [19][20][21][22][23]: The PV cell temperature, Tc, is influenced by various factors such as solar radiation, ambient conditions, and wind speed. It is well known that the cell temperature impacts the PV current and performance, and its time variation can be determined from references [19][20][21][22][23].…”

“…Nanofluids have excellent thermal conductivity [1][2][3][4][5][6][7][8][9][10][11] and have been applied as the working fluids in traditional heat pipe applications to enhance thermal performance. "In the presence of an external magnetic field, the thermal conductivity of magnetite nanofluids increases with the increase in the volumetric concentration of magnetic particles, which is associated with the increase in the magnetic field strength" [12][13][14][15][16][17][18][19][20][21][22][23][24].…”

“…It was reported by Katiyara et al [20] that "a magnetic field induced augmented thermal conductivity of a magnetonanocolloid involving magnetic oxide nanoparticles, Fe 2 O 3 , Fe 3 O 4 , nickel oxide (NiO), and cobalt oxide (Co 3 O 4 ) dispersed in different base fluids such as heat transfer oil, kerosene, and ethylene glycol. Experiments revealed that the augmented thermal transport under the external applied magnetic field, with kerosenebased MNCs, showed relatively low magnetic field (~600 G) intensities as compared to the heat transfer oil and EG-based MNCs.…”

“…Additionally, it was observed that Co 3 O 4 nanoparticles showed an insignificant effect on the thermal conductivity enhancement of MNCs due to their minimal magnetic moment". Katayama et al [20] "proposed an analytical approach to understanding the mechanism and physics behind the thermal conductivity enhancement under the external applied magnetic field, in tune with the near field magnetostatic interactions as well as Neel relaxivity of the magnetic nanoparticles. Furthermore, their analytical model predicted the phenomenon of enhanced thermal conductivity as a function of physical parameters such as chain length, size, and types of nanoparticles, fluid characteristics, magnetic field intensity, saturation magnetic moment, and nanoparticle concentration and had a good agreement with the experimental results was observed".…”