Optical characterisation and photothermal conversion efficiency of a water-based carbon nanofluid for direct solar absorption applications

Abstract

Carbon nanoparticles are very useful in solar thermal applications as they absorb much of the solar spectrum and can be inexpensive. Water-based carbon nanofluids with two different concentrations (3 and 33 mg•l-1) were prepared with sodium dodecyl sulphate as surfactant to achieve good high-temperature stability with a constant mean particle size of 200 nm at 25 °C and 85 °C. The morphology of the nanoparticles was observed by Transmission Electron Microscopy and the particle size distribution was studied using Dynamic Light Scattering at room and high temperature. Ballistic transmittance, absorption coefficient and scattering albedo of the three fluids were measured by a spectrophotometer with and without an integrating sphere using the Kubelka-Munk theory. The average value of the absorption coefficient showed important increases when comparing water against the nanofluid with the highest concentration (from 0.1 to 3.3 cm-1). Finally, the temperature change achieved when lighting the samples with an artificial sunlight simulator were measured and photothermal conversion efficiencies were evaluated, with increases of up to 200 % when comparing nanofluid and base fluid. The results of this study show this kind of nanofluids to be very interesting for increasing the overall efficiency of the direct absorber solar collectors.

Measurement of the Photothermal Conversion Efficiency of CNT Films Utilizing a Raman Spectrum

“…Carbon nanotubes (CNTs) are widely used in seawater desalination [ 1 , 2 , 3 , 4 , 5 , 6 ], environmental protection [ 7 ], thermal energy storage [ 8 , 9 , 10 , 11 ], photothermal dynamic therapy [ 12 , 13 , 14 ], and photodetectors [ 15 , 16 , 17 , 18 ] because of their efficient photothermal conversion ability. However, the synthesis process of CNTs is difficult to control strictly, which often induces complex morphologies and chirality distribution; simultaneously, some defects and impurities are also introduced.…”

Thermohydraulic performance improvement and entropy generation characteristics of a microchannel heat sink cooled with new hybrid nanofluids containing ternary/binary hybrid nanocomposites

“…Nanofluids can possess heat transfer capabilities higher than base fluids can. [9][10][11][12] Recently, advances in nanofluids have led to the invention of fluids exhibiting a large number of interesting features; these fluids are known as hybrid nanofluids. 13 Compared with mono nanofluids and conventional coolants, hybrid nanofluids can possess a superior thermal conductivity and a higher heat transfer capability.…”

Characterisation of optical properties of solar nanofluids by an inverse problem based on a numerical model

“…With regard to the experimental results for the formulation of the inverse problem, these were directly measured in a laboratory by making use of the experimental setup described in the work of Gimeno-Furió et al [8]. To sum up, this experimental setup (see Figure 1) consists of a quartz glass tube in which the nanofluids were placed and which was irradiated by an artificial sunlight simulator.…”