| 1. |
- Du, Jianqiang, et al.
(author)
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Experimental study of pool boiling performance of Fe3O4 ferromagnetic nanofluid on a copper surface
- 2024
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In: Applied Thermal Engineering. - 1359-4311. ; 248
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Journal article (peer-reviewed)abstract
- Nanofluids significantly enhance the critical heat flux of boiling heat transfer. This paper experimentally investigates the pool boiling performance and the influence mechanism of Fe3O4 nanofluids. Compared with deionized water, the 0.001 vol% nanofluid increases a maximum enhancement in critical heat flux by 47.90%. During nanofluid boiling, Fe3O4 nanoparticles are deposited on the surfaces. The nanoparticle deposition surfaces are physically characterized to explain the influence mechanism of Fe3O4 nanoparticles on boiling heat transfer. Nanoparticle deposition modifies the surface micro-morphology, which increases roughness and improves wettability. The changes are essential factors for the enhancement of the critical heat flux. This paper further analyses the boiling results of deionized water on the nanoparticle deposition surfaces. Compared with a polished surface, the critical heat flux and heat transfer coefficient of the nanoparticle deposition surface show maximum increases of 52.39% and 56.19%. Due to the similar enhancement of critical heat flux using the Fe3O4 nanofluid and the nanoparticle deposition surface, it is found that the increased critical heat flux of the nanofluids is attributed to the improvement of surface wettability and roughness by nanoparticle deposition. This study analyzes the mechanism of Fe3O4 nanofluid for enhancing pool boiling heat transfer from the perspective of modifying boiling surface characteristics by nanoparticle deposition, especially in wettability and roughness, which advances the understanding of enhanced boiling heat transfer by nanofluids.
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| 2. |
- Wang, Jin, et al.
(author)
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Experimental investigation on convective heat transfer of ferrofluids inside a pipe under various magnet orientations
- 2019
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In: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 132, s. 407-419
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Journal article (peer-reviewed)abstract
- Some experimental tests were conducted to reveal the enhancement of the ferrofluid heat transfer under a permanent magnetic field. This research aims to investigate the effect of various external magnetic fields on convective heat transfer characteristics of the ferrofluid (magnetic nanofluid). Comparison of theoretical predictions and experimental data were conducted to validate the rationality of the test results, and a good agreement with less than 10% deviations was found. The deviations from experimental data decrease with an increase of the Reynolds number (Re) from 391 to 805. Results from the case with 5 cannulas indicate that a continuous increase in the magnetic flux density (by increasing the quantity of the magnets) can improve the heat transfer enhancement significantly. The ferrofluids with a magnetic cannula shows heat transfer enhancements of 26.5% and 54.5% at Re = 391 and 805, respectively.
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| 3. |
- Wang, Jin, et al.
(author)
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Numerical investigation of particle deposition in film-cooled blade leading edge
- 2020
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In: Numerical Heat Transfer; Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 77:6, s. 579-598
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Journal article (peer-reviewed)abstract
- This study numerically investigates film-cooling performance and particle trajectories in AGTB (two rows of cylindrical holes equipped on suction side (SS) and pressure side (PS) of the leading edge, respectively) turbine cascade. Particle deposition on a turbine blade is analyzed by calculations of capture efficiency and impact efficiency. The turbulent flow is modeled by the Realizable k-ε turbulence model, and the discrete phase model (DPM) with user-defined functions (UDFs) is used to simulate the particle motions. An invasion efficiency is proposed to analyze the possibility of particle invasion into the film hole. Comparisons of various particles with diameters of 1 µm, 5 µm, 10 µm, 20 µm, and 50 µm, respectively, are conducted for four blowing ratios (0.53, 0.93, 1.31, 1.63) and three inlet flow angles (123°, 133°, and 143°). It is observed that with a small inlet flow angle and a large blowing ratio, the capture efficiency on the PS decreases. It is found that smaller particle size results in lower invasion efficiency, and larger particles are more likely to invade into the film-cooling hole especially at a low blowing ratio.
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