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

Heat transfer of nanoparticle suspensions in turbulent pipe flow is analyze theoretically.The main idea upon which this lead is found is that nanofluids behave more standardised singlephasefluids than like conventional unfluctuatingityliquid mixtures. This assumption implies thatall the convective fondness transfer correlations available in the literature for single-phaseflows can be broaden to nanoparticle suspensions, provided that the thermophysicalproperties appearing in them be the nanofluid effectual properties calculated at the fiber temperature. In this regard, two empirical equations, based on a gigantic varietyof experimental data reported in the literature, are utilize for the evaluation of thenanofluid effective thermal conductivity and dynamic viscosity. Conversely, the othereffective properties are computed by the traditional mixing theory. The novelty of thepresent poll is that the merits of nanofluids with respect to the corresponding baseliquid are evalua ted in wrong of global energetic writ of execution, and not simply by thecommon forefront of view of the heat transfer enhancement. Both cases of unendingpumping power and unremitting heat transfer rate are investigated for different operatingconditions, nanoparticle diameters, and solidliquid combinations. The fundamentalresult obtained is the existence of an optimal particle consignment for either maximum heattransfer at constant brainish 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 slew temperature is increased, the Reynolds number of the base fluid isincreased, and the length-to-diameter ratio of the pipe is decreased, while it is a great deal independent of the nanoparticle diameter.The usual design requirements for modern heat transfer equipment are reduced size andhigh thermal perfor mance. In this connection, in the sometime(prenominal) decades a considerableresearch effort has been dedicated to the development of advanced(a) 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, check to a number of studies executed in recent times, a supercharge importantcontribution 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 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 domain of convection in nanofluids, clearly show thatnanoparticle suspensions offer better thermal performance than the base liquids at sameReynolds number, and that heat transfer increases with increasing the nanoparticle