From new materials to innovative structures
1. Nanofluids are the trademark of fluids laden with metallic, oxide or carbon-based particles of nanoscale that may have spherical or elongated shape. The suspended nanoparticles exhibit properties unlike those of either the nanoparticles or the base fluid. For instance, viscosity, heat conductivity and other transport properties can be significantly and usefully modified.
2. Many types of industry need fluids with much higher viscosity, thermal conductivity and other rheological properties than can be found today on the market.
Among applications are collectors in concentrated solar power systems, cooling of electronics, internal combustion engines, and lubrication in general, both on ground and in space. For example, heat transfer enhancement in sunlight exploiting devices is a critical point for the improvement of the overall system efficiency and compactness. Moreover, many nanofluids dramatically increase sunlight absorption, property crucial for solar heating systems. In particular, nanofluids laden with the multiwall-carbon-nanotubes (consisting of several annular layers of rolled up graphene sheets held together by interlayer van der Waal’s forces) are expected to exhibit superior heat transfer properties compared with conventional heat transfer fluids (and other type of nanofluids) and to have much better absorption properties. However, their stability (with respect to the sedimentation and to degradation) is still very questionable and strongly depends on the flow characteristics.
3. Suggested project will include our research and development of solar-thermal systems in large-scale industrial sectors, aiming to increase their efficiency, to lower their cost and to further reduce environmental impacts. We will be based on recent idea to use nanofluids instead of conventional heat-transfer fluids, like water or oils (synthetic-mineral)
Notice that effective choice of optimal (or close to that) of type of nanofluids and flow regimes cannot be based only on laboratory tests: their required number is far above any reasonable level. This is because of huge variety of nanofluids (with different particle size and shape, particle material, type of the base fluid, preparation techniques, etc.), various flow regimes (from laminar with small and moderate Reynolds numbers to fully developed turbulent with very different Reynolds, Peclet, Debora and other numbers, characterizing numerous aspects of relevant physical mechanisms of the heat transport), different character of the light absorption and different corrosive resistance.
Clearly, optimal choice of nanofluid in each particular region of application
has to be global and thus impossible without appropriate modeling, based on adequate description of complicated physical processes, governing nanofluid behaviour in realistic flows. Unfortunately, to-date, there is no physically-based understanding of how and why nanofluid work. Corresponding studies are still in its infancy stage: they either are dealing with oversimplified, non-realistic situations (e.g. fluid is at rest) or full of empirical and often contradictory explanations. Experimental results are also often contradictory, probably because of difficulties in controlling relevant parameters and, as a rule, dealing with resting fluids or with low Reynolds laminar flows.