| 1. |
- Wang, Jin, et al.
(författare)
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Effect of various surfactants on stability and thermophysical properties of nanofluids
- 2020
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Ingår i: Journal of Thermal Analysis and Calorimetry. - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926.
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Fe3O4 nanoparticles and carbon nanotubes (CNTs) on the viscosity of a nanofluid is experimentally investigated from 278 to 313 K by changing the nanoparticle volume fraction. These nanoparticles were put into distilled water with various surfactants, i.e., Colace (docusate sodium), trisodium citrate dihydrate (TSC), polyvinyl pyrrolidone, cetyl trimethylammonium bromide, tetramethylammonium hydroxide (TMAH), acacia senegal (GA), sodium dodecyl benzene sulfonate, sodium dodecyl sulfate (SDS), and sodium laurylsulfonate (SLS). Based on the present measurements, new empirical formulas are proposed for Fe3O4–water, CNT–water and Fe3O4–CNT–water nanofluids to provide accurate predictions for the nanofluid viscosity. Based on the viscosity testing, stabilities and thermal conductivities of Fe3O4–TMAH, Fe3O4–Colace, Fe3O4–TSC, CNT–SDS, CNT–GA, Fe3O4–CNT–SLS, and Fe3O4–CNT–TSC nanofluids with a volume concentration of 0.5% are investigated in the present research. Results indicate that better stability, smaller viscosity, and higher thermal conductivity are obtained, when the surfactants TMAH, SDS, and SLS are added into the Fe3O4–water, CNT–water, and the Fe3O4–CNT–water nanofluid, respectively. The CNT–water and Fe3O4–CNT–water nanofluids exhibit a shear-thinning behavior, whereas a linear rheological behavior can be observed by water-based Colace–Fe3O4, TMAH–Fe3O4, and TSC–Fe3O4 nanofluids.
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| 2. |
- Zhen, Hongyu, et al.
(författare)
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Inverted indium-tin-oxide-free cone-shaped polymer solar cells for light trapping
- 2012
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 100:21, s. 213901-
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Tidskriftsartikel (refereegranskat)abstract
- Based on the flexibility of polymer film, cone-shaped polymer solar cells (PSCs) are fabricated and studied. Effective light trapping is achieved due to multi-absorption in all 360 degrees directions. Monte Carlo ray tracing is used to simulate the absorption of cone-shaped PSCs with two variables: wavelength and half cone angle. With an inverted indium-tin-oxide-free device structure, a 43% enhanced light utilization without loss of material utilization is realized in the cone-shaped PSCs with a half cone angle of 45 degrees, compared with the planar PSCs.
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| 3. |
- Heitz, Thomas, et al.
(författare)
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Investigation on eXtreme Gradient Boosting for cutting force prediction in milling
- 2023
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Ingår i: Journal of Intelligent Manufacturing. - : Springer. - 0956-5515 .- 1572-8145.
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Tidskriftsartikel (refereegranskat)abstract
- Accurate prediction of cutting forces is critical in milling operations, with implications for cost reduction and improved manufacturing efficiency. While traditional mechanistic models provide high accuracy, their reliance on extensive milling data for force coefficient fitting poses challenges. The eXtreme Gradient Boosting algorithm offers a potential solution with reduced data requirements, yet the optimal utilization of eXtreme Gradient Boosting remains unexplored. This study investigates its effectiveness in predicting cutting forces during down-milling of Al2024. A novel framework is proposed optimizing its precision, efficiency, and user-friendliness. The model training incorporates the mechanistic force model in both time and frequency domains as new features. Through rigorous experimentation, various aspects of the eXtreme Gradient Boosting configuration are explored, including identifying the optimal number of periods for the training dataset, determining the best normalization and scaling technique, and assessing the hyperparameters’ impact on model performance in terms of accuracy and computational time. The results show the remarkable effectiveness of the eXtreme Gradient Boosting model with an average normalized root mean square error of 14.7%, surpassing the 21.9% obtained by the mechanistic force model. Additionally, the machine learning model could capture the runout effect. These findings enable optimized milling operations regarding cost, accuracy and computation time.
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| 4. |
- Li, Guolong, et al.
(författare)
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Improvement of cooling performance of hybrid nanofluids in a heated pipe applying annular magnets
- 2022
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Ingår i: Journal of Thermal Analysis and Calorimetry. - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926. ; 147:7, s. 4731-4749
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, convective heat transfer of Fe3O4–carbon nanotubes (CNTs) hybrid nanofluid was studied in a horizontal small circular tube under influence of annular magnets. The pipe has an inner diameter of 3 mm and a length of 1.2 m. Heat transfer characteristics of the Fe3O4–water nanofluid were examined for many parameters, such as nanoparticle volume fraction in the range of 0.4–1.2% and Reynolds number in the range of 476–996. In order to increase the thermal conductivity of the Fe3O4–water nanofluid, carbon nanotubes with 0.12–0.48% volume fraction were added into the nanofluid. It was observed that for the Fe3O4–CNTs–water nanofluid with 1.44% volume fraction and under a magnetic field, the maximal local Nusselt number at the Reynolds number 996 increased by 61.54% compared with without a magnetic field. Results also show that compared with the deionized water, the maximal enhancements of the average Nusselt number are 67.9 and 20.89% for the Fe3O4–CNTs–water nanofluid with and without magnetic field, respectively.
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| 5. |
- Wang, Jin, et al.
(författare)
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Experimental investigation on convective heat transfer of ferrofluids inside a pipe under various magnet orientations
- 2019
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 132, s. 407-419
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Wang, Jin, et al.
(författare)
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Investigation of mixed convection in an enclosure filled with nanofluids of Al2O3 –water and graphene-ethylene glycol
- 2019
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Ingår i: Journal of Nanofluids. - : American Scientific Publishers. - 2169-432X. ; 8:2, s. 337-348
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Tidskriftsartikel (refereegranskat)abstract
- In this research work, heat transfer enhancement of mixed convection in an enclosure is investigated with a moving top wall. Numerical simulations based on an Al2 O3 –water nanofluid are conducted by using variable thermophysical properties. Flow fields and temperature distributions are analyzed by considering effects of two partially heated walls. Moreover, water–ethylene glycol mixed with graphene nanoplatelets (GnP-WEG) is also considered to analyze effects of the heating procedure, Reynolds number, Rayleigh number and volume fraction of the nanoparticles, as well as on the heat transfer enhancement. It is found that there is a velocity difference between the pure water and the Al2 O3 –water nanofluid due to the increase of the fluid viscosity by an injection of Al2 O3 nanoparticles into the water. Moreover, flow patterns are significantly affected by the Reynolds number and the Rayleigh number. The heat transfer in the enclosure is enhanced by the increase of the top wall moving velocity. Although heat transfer enhancement for most cases are obtained by increasing the volume fraction of graphene nanoplatelets, a mixture of 0.25% graphene nanoplatelets and the water–ethylene glycol (the base fluid) provides the largest enhancement of heat transfer at low Reynolds number (Re = 1).
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