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Nanofluid optical property characterization: towards efficient direct absorption solar collectors.

Taylor RA, Phelan PE, Otanicar TP, Adrian R, Prasher R - Nanoscale Res Lett (2011)

Bottom Line: To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known.A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient.Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

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Affiliation: Arizona State University, Tempe, AZ, USA. Rataylo2@asu.edu.

ABSTRACT
Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

No MeSH data available.


Diagram of the three-slab system representation for a spectrometry measurement of a nanofluid-filled quartz cuvette.
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Figure 4: Diagram of the three-slab system representation for a spectrometry measurement of a nanofluid-filled quartz cuvette.

Mentions: Regardless of the spectrophotometer used, some further calculations are necessary to obtain extinction coefficients for nanofluids. Since a cuvette contains the liquid sample in the system, the resulting measurement is actually that of a 'three-slab system'. This adds complexity since there can be multiple reflections at each interface which needs to be taken into account in the measurements. Figure 4 shows the details of this multi-component system.


Nanofluid optical property characterization: towards efficient direct absorption solar collectors.

Taylor RA, Phelan PE, Otanicar TP, Adrian R, Prasher R - Nanoscale Res Lett (2011)

Diagram of the three-slab system representation for a spectrometry measurement of a nanofluid-filled quartz cuvette.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211283&req=5

Figure 4: Diagram of the three-slab system representation for a spectrometry measurement of a nanofluid-filled quartz cuvette.
Mentions: Regardless of the spectrophotometer used, some further calculations are necessary to obtain extinction coefficients for nanofluids. Since a cuvette contains the liquid sample in the system, the resulting measurement is actually that of a 'three-slab system'. This adds complexity since there can be multiple reflections at each interface which needs to be taken into account in the measurements. Figure 4 shows the details of this multi-component system.

Bottom Line: To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known.A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient.Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

View Article: PubMed Central - HTML - PubMed

Affiliation: Arizona State University, Tempe, AZ, USA. Rataylo2@asu.edu.

ABSTRACT
Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

No MeSH data available.