Nanofluid refers to the dispersion of metal or non-metallic nano-powders into traditional heat transfer media such as water, alcohol, oil and so on to prepare a new type of heat transfer medium with uniformity, stability and high thermal conductivity. This is innovative research on the application of nanotechnology in the traditional field of thermal energy engineering. Hybrid fluid refers to the nanofluid containing two or more kinds of metallic or non-metallic nano-powders, which has great potential applications in the fields of energy, chemical industry, automobile, architecture, microelectronics, information and so on. It has become a research hotspot in the fields of materials, physics, chemistry, heat transfer and so on.
- The field of optics: Smart materials can produce useful effects in response to external stimuli (such as strain, stress, temperature, pH, and electric and magnetic fields). Rheological (ER) fluids are smart materials, and their rheology changes when exposed to an external electric field. Nanoparticle-based hybrid fluids display many advantages applicable to ER fluids, such as low density, better stability against sedimentation, and low wear of the fluid vessel. For example, BaTiO3 nanoparticles synthesized by the hydrolysis of Ba-Ti bisalkoxide are often used In a heterogeneous ER fluid. The transparent fluid synthesized with perovskite-type BaTiO3 particles through a chemical process shows field-responsive rheological behavior and optical transmittance.
Figure 1. BaTiO3 particles/siloxane fluid appearance and TEM and DLS analysis chart.
- Machinery field: Piston-based micro engines mostly suffer from friction loss and leakage due to the cylinder-piston gap, which is not conducive to the operation of the engine. Therefore, the membrane is the first choice for miniaturization. However, their natural frequencies are a key aspect of optimization because they require low values that match the characteristic time of the micromechanical cycle. The Hybrid Fluid Membrane (HFM) can be used as an alternative piston, providing a technical solution for low-frequency micro-engines. Some researchers have prepared a hybrid fluid membrane, which is a composite structure based on Silicon spiral springs embedded in a polymer (RTV silicone), and its dynamic characteristics prove the consistency between experimental and theoretical results.
Figure 2. Microfabrication steps from free suspended RTV silicone membrane to HFM structures.
- Heat transfer field: Nanofluids have a wide range of applications in the field of enhanced heat transfer due to their special physical and chemical properties. Because of the large specific surface area of the nanoparticles in the nanofluid, adding to the liquid increases the surface area of the solid and liquid phases and enhances the heat capacity of the fluid, which makes it have a great advantage in heat transfer.
- Refrigeration field: Nanofluids have also been widely used in the field of refrigeration. Some researchers synthesized and prepared water-based carbon nanotube hybrid nanoflows, and used X-Y function recorders to study the refrigeration characteristics of the nanofluids. The results show that the thermal conductivity of the fluid with nanofluid dispersant is much higher than that of the fluid without nanofluid dispersant, which demonstrates the superiority of nanofluids in refrigeration.
In addition, nanofluids are also used in metallurgy, biomedicine, preparation of high-efficiency heat exchangers, as lubricants and so on.
- Ken-ichi Mimura. (2010) "Synthesis of Transparent and Field‐Responsive BaTiO3 Particle/Organosiloxane Hybrid Fluid" Angew.chem. 49(29):4902-4906.
- R Chutani.(2015) "Microfabrication of hybrid fluid membrane for microengines." J. Phys.: Conf. Ser. 660:012048.