Heat transfer of nanofluids in turbulent pipe flow :: Technology, Nanofluids

awake delight of nanoparticle suspensions in turbulent pipe flow is studied theoretically.The briny idea upon which this work is imbrutedd is that nanofluids behave more homogeneous singlephasefluids than like conventional solid facile mixtures. This assumption implies thatall the convective wake transfer correlations available in the literature for single-phaseflows can be extended to nanoparticle suspensions, provided that the thermophysicalproperties be in them are the nanofluid effective properties calculated at thereference temperature. In this regard, two empirical equations, based on a wide variantof experimental data reported in the literature, are used for the military rating of thenanofluid effective thermal conductivity and dynamic viscosity. Conversely, the othereffective properties are computed by the traditional mixing theory. The novelty of thepresent study is that the merits of nanofluids with treasure to the corresponding base unruffled are evaluated in term s of planetary energetic performance, and not simply by thecommon point of follow of the inflame transfer enhancement. Both cases of constantpumping strength and constant shake up transfer rate are investigated for different operatingconditions, nanoparticle diameters, and solidliquid combinations. The fundamentalresult obtained is the existence of an optimal particle loading for either maximum shake uptransfer at constant driving power or minimum cost of operation at constant heattransfer rate. In particular, for any assigned combination of solid and liquid phases, it isfound that the optimal concentration of suspended nanoparticles increases as thenanofluid bulk temperature is increased, the Reynolds design of the base fluid isincreased, and the length-to-diameter ratio of the pipe is decreased, while it ispractically mugwump of the nanoparticle diameter.The usual design requirements for modern heat transfer equipment are bring down size andhigh thermal performance. In th is connection, in the past decades a considerableresearch effort has been dedicated to the development of advanced methods for heattransfer enhancement, such as those relying on new geometries and configurations, andthose based on the use of extended surfaces and/or turbulators. On the other hand,according to a number of studies executed in recent times, a further greatcontribution may derive by the replacement of traditional heat transfer fluids, such aswater, ethylene glycol and mineral oils, with nanofluids, i.e., colloidal suspensions ofnano-sized solid particles, whose effective thermal conductivity has been demonstratedto be higher(prenominal) than that of the corresponding pure base liquid.The main results of prior work on pipe flow, that is undoubtedly one of the mostinvestigated topics in the field of convection in nanofluids, clearly show thatnanoparticle suspensions offer better thermal performance than the base liquids at sameReynolds number, and that heat transfer incr eases with increasing the nanoparticle