Abstract
This work presents an optical fiber dynamic light scattering sensor capable of simultaneously assessing concentration and flow speed of nanofluids. Silica nanoparticles (189 nm) in water were tested, yielding a sensitivity of 0.78288 × 10³ s−1 for static conditions. Then, the sensor was submitted to situations that simulate spatial concentration changes, offering better results than those obtained by traditional mathematical models. Finally, in flow tests, the light backscattered by the nanoparticles were collected by a fiber probe placed parallel to the streamline, whereas intensity values were processed by artificial neural networks. The sensor provides average errors of 0.09 wt% and 0.26 cm/s for concentration and speed measurements, respectively, and can be further applied to assess different types of nanofluids and inline processes.
Highlights
Nanofluids are stable suspensions of nanoparticles in a base-fluid, and their physical and chemical properties can be tailored according to the characteristics of both dispersed and continuous phases [1]
The optical fiber sensors (OFS) was used to evaluate the clarified zone during the experiment, but no dynamic light scattering (DLS) phenomenon was observed, suggesting that the zone is approximately free of particles
A minimum point of the function or an oscillation of the baseline may be observed, and they are caused by experimental deviations or by the discretization errors involved in the mathematical processing of the signal by the algorithm in Equations (1)–(6) [12,19]
Summary
Nanofluids are stable suspensions of nanoparticles in a base-fluid, and their physical and chemical properties can be tailored according to the characteristics of both dispersed and continuous phases [1]. Silica particles present advantages in terms of sphericity and surface properties; silica-based nanofluids have been developed for use in thermal conductivity enhancement [2], in-vivo fluorescence imaging [3], and tunable optical filters [4] In this sense, the assessment of micro and nanoparticles subjected to flow and other dynamic conditions (e.g., concentration gradients and disturbances) is essential for silica nanofluids applications, and for several other biochemical, biomedical, and food engineering uses, such as the monitoring of red cells in blood streams [5], the flow of polymeric particles (e.g., polystyrene) obtained by chemical emulsion processes [6], and the nanoencapsulation of nutrients based on food emulsions [7]. The ultrasonic sensors are generally based on the use of piezoelectric materials, and rely on transducers, which transform an electric signal into an acoustic wave and vice versa
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