Synthesis of Low Viscous Dielectric Nanofluids and Characterization of Convection Heat Transfer

Kim, Joong Bae; Jeong, Mun Goung; Lee, Bong Jae

doi:10.2514/1.t5353

Cited by 4 publications

(7 citation statements)

References 62 publications

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“…Therminol VP‐1, which is a synthetic heat transfer fluid, is chosen as the base fluid considering its thermal stability up to 400°C and its attractive thermophysical properties; that is, moderate thermal conductivity ( k = 0.136 W/m⋅K at 20°C) and low viscosity ( μ = 4.29 mPa⋅s at 20°C) with specific heat of 1546 J/kg⋅K and density of 1056 kg/m 3 at 20°C for effective heat transfer 23 . Graphite nanopowders (GNs), which are the same as those in the earlier work, 24 are suspended to tune the absorption coefficient of Therminol VP‐1. According to Kim et al, 24 GNs (99.99% purity) in spherical shape have 150 nm of average diameter, which is smaller than the wavelength of the solar spectrum (refer to the SEM image in the aforementioned reference).…”

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

“…Graphite nanopowders (GNs), which are the same as those in the earlier work, 24 are suspended to tune the absorption coefficient of Therminol VP‐1. According to Kim et al, 24 GNs (99.99% purity) in spherical shape have 150 nm of average diameter, which is smaller than the wavelength of the solar spectrum (refer to the SEM image in the aforementioned reference). It is also expected for GNs to have the advantage of low mechanical loss (ie, pump work) in DASCs compared to carbon nanotubes (CNTs) because CNTs having a length in the order of microns greatly increase the viscosity of the nanofluids 24 .…”

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

“…According to Kim et al, 24 GNs (99.99% purity) in spherical shape have 150 nm of average diameter, which is smaller than the wavelength of the solar spectrum (refer to the SEM image in the aforementioned reference). It is also expected for GNs to have the advantage of low mechanical loss (ie, pump work) in DASCs compared to carbon nanotubes (CNTs) because CNTs having a length in the order of microns greatly increase the viscosity of the nanofluids 24 . To improve the dispersion stability of GNs in Therminol VP‐1, surfactant (Triton X‐100, Sigma‐Aldrich) is employed.…”

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

“…To characterize the dispersion stability of TG nanofluids, the transmittance of TG nanofluids is measured using a UV‐VIS spectrophotometer (UV‐3600 Plus, Shimadzu) in a 10‐mm‐thick SiO 2 cuvette 18,24 . The uncertainty of transmittance measurements was estimated to be 0.01 25 .…”

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

“…The transmittance of TG nanofluids had been monitored for 4 weeks to check the evolution of dispersion stability 24 . Because nanoparticles are substantive absorber in nanofluids, transmittance of nanofluids increases as nanoparticles settle down.…”

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

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Synthesis of therminol‐graphite nanofluids and photo‐thermal conversion properties

et al. 2021

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Summary Therminol‐based nanofluids with graphite nanopowders (GNs) were proposed as an efficient working fluid in direct‐absorption solar collectors (DASCs), especially for elevated‐temperature applications. In this work, Therminol VP‐1/GN nanofluids (TG nanofluids) were prepared in two steps with surfactant (Triton X‐100). In the synthesis procedure, the vortex generator for coating GN with sticky surfactant (μ = 240 mPa⋅s) and the ultra‐sonicator for diluting GN/Triton X‐100 mixture with Therminol VP‐1 are used. We have demonstrated excellent dispersion stability up to 4 weeks and even after heating over 100°C without any surface modification of nanoparticles. The feasibility of using the synthesized TG nanofluid as a working fluid in DASCs was experimentally demonstrated by measuring its absorption coefficient as well as by characterizing photo‐thermal conversion performance. The absorption coefficient of the TG nanofluid at 0.004 wt.% of GNs was measured to be 1.12 cm−1, which is more than eight times enhanced from that of bare Therminol VP‐1 (ie, 0.13 cm−1) in the wavelengths from 350 to 1600 nm. Finally, the temperature increment of 43°C was achieved after t = 3600 s under the 5‐sun condition in the static photo‐thermal conversion experiment. Moreover, the low viscosity of TG nanofluids (only 2.2% higher than that of the bare Therminol VP‐1) supports the superiority of TG nanofluids to be applied as working fluid in DASCs.

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Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

Section: Synthesis Of Tg Nanofluids and Characterization Of Optical Propertiesmentioning

confidence: 99%

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Synthesis of therminol‐graphite nanofluids and photo‐thermal conversion properties

et al. 2021

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Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids

2019

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A parabolic trough solar collector is a dominant technology for high-temperature industrial applications, but efficient use of a conventional surface-based parabolic trough solar collector (SBPTSC) is limited by its high radiation loss due to the high surface temperature. Recently, direct-absorption parabolic trough solar collector (DAPTSC) using nanofluids has been proposed, and its thermal efficiency has been reported to be 5-10% higher than the conventional SBPTSC for inlet temperature up to 250 • C. However, the inner tubes of the receivers of the existing DAPTSCs are all transparent, so the sun rays entering the inner tube can only travel once through the nanofluids. As a result, the optical path length for the sun rays is limited by the inner tube size, which in turn requires high value of the absorption coefficient of nanofluids. Due to the approximately linear relation between the absorption coefficient and the particle concentration, higher absorption coefficient is likely to cause particle agglomeration, leading to detrimental effects on maintaining stable collector performance. In the current study, the transparent DAPTSC is improved by applying a reflective coating on the upper half of the inner tube outer surface, such that the optical path length is doubled compared to the transparent DAPTSC; thus, the absorption coefficient of the nanofluids can be reduced accordingly. The coated DAPTSC is found to have obvious advantage compared to the transparent DAPTSC at absorption coefficient below 0.5 cm −1 for a receiver with inner tube diameter of 7 cm. In addition, performance of the transparent DAPTSC, the coated DAPTSC and the SBPTSC with black chrome coating have been compared to explore their advantageous operation conditions, such as inner tube diameter, flow rate, and inlet temperature, with or without a glass envelope for vacuum evacuation. The findings in this study will facilitate the use of nanofluids in a parabolic trough solar collector with more stability and provide a guide for choosing suitable type of parabolic trough solar collectors for specific working conditions.

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Synthesis of Therminol-based plasmonic nanofluids with core/shell nanoparticles and characterization of their absorption/scattering coefficients

Lee

Kim

Qin

et al. 2020

Solar Energy Materials and Solar Cells

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Synthesis of Low Viscous Dielectric Nanofluids and Characterization of Convection Heat Transfer

Cited by 4 publications

References 62 publications

Synthesis of therminol‐graphite nanofluids and photo‐thermal conversion properties

Synthesis of therminol‐graphite nanofluids and photo‐thermal conversion properties

Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids

Synthesis of Therminol-based plasmonic nanofluids with core/shell nanoparticles and characterization of their absorption/scattering coefficients

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