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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.

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.


Extinction coefficients for Therminol VP-1-based "solar nanofluids". Bottom curve shows experimental results for the pure base fluid, Therminol VP-1.
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Figure 7: Extinction coefficients for Therminol VP-1-based "solar nanofluids". Bottom curve shows experimental results for the pure base fluid, Therminol VP-1.

Mentions: Figure 7 shows similar plots for various nanofluids which have Therminol VP-1 (Solutia Inc, St. Louis, MO, USA) as a base fluid. Therminol VP-1 is a type of heat transfer fluid which is commonly used in many solar collectors. It is a colorless liquid which is only slightly more viscous than water and has a much higher boiling point, approximately 257°C. This ability to work at higher temperature makes it applicable for medium-temperature solar collectors. It is composed of approximately 26.5% biphenyl and 73.5% diphenyl oxide. Unfortunately, there is very little information on the optical properties of these materials. Thus, the experimentally determined properties for the base fluid are used in the modeled extinction coefficients in Figure 7. Very similar trends are present to those seen in Figure 6, except that the absorption of the base fluid is less dominant at longer wavelengths.


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

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

Extinction coefficients for Therminol VP-1-based "solar nanofluids". Bottom curve shows experimental results for the pure base fluid, Therminol VP-1.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Extinction coefficients for Therminol VP-1-based "solar nanofluids". Bottom curve shows experimental results for the pure base fluid, Therminol VP-1.
Mentions: Figure 7 shows similar plots for various nanofluids which have Therminol VP-1 (Solutia Inc, St. Louis, MO, USA) as a base fluid. Therminol VP-1 is a type of heat transfer fluid which is commonly used in many solar collectors. It is a colorless liquid which is only slightly more viscous than water and has a much higher boiling point, approximately 257°C. This ability to work at higher temperature makes it applicable for medium-temperature solar collectors. It is composed of approximately 26.5% biphenyl and 73.5% diphenyl oxide. Unfortunately, there is very little information on the optical properties of these materials. Thus, the experimentally determined properties for the base fluid are used in the modeled extinction coefficients in Figure 7. Very similar trends are present to those seen in Figure 6, except that the absorption of the base fluid is less dominant at longer wavelengths.

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.