Characteristic features of nanofluids application in power engineering

The problem of increasing the intensity of heat transfer is an urgent and important task. Methods of increasing the heat transfer coefficient in cooling systems of power equipment are of particular interest. Over the past two decades, a promising area of research in this area is the study of heat transfer using nanofluids. To date, domestic and foreign authors have performed a large amount of research. The scientific search is conducted in several directions: the choice of a heat-conducting material and a base fluid; the study of the influence of nanoparticle concentration and size on the intensity of heat exchange. To increase the thermal conductivity of the heat transfer agents, it is proposed to use both pure metals (Au, Cu, Fe), their oxides (CuO, Al 2 O 3 , TiO 2 ), and carbon nanomaterials. The base fluid is mainly distilled water, mineral oil, or ethylene glycol. Almost all authors note an increase in the thermal conductivity of the nanofluid up to 40% on average compared to the base fluid. The concentration of nanoparticles in experiments does not exceed 4%. However, the studies performed often give results that significantly contradict the theory of convective heat transfer. Thus, many authors note that the heat transfer coefficient in the laminar mode of the nanofluid is greater than that of the base fluid, and the reverse is observed in the turbulent mode. A convincing explanation for this phenomenon has not yet been found. There is also no reliable data on the portable properties of materials used for the manufacture of nanofluid, in particular, there is little data on the properties of nanographene. In the article, the authors review the studies of heat transfer using nanofluid, consider the possibility of using nanotubes and multigraphen to increase the thermal conductivity of the heat transfer agent. The authors also analyze existing models of heat transfer in nanofluids.