Flow And Heat Transfer Characteristics Of Nanofluid In Twisted-tape Inserts In Tubes

Enhancement of heat transfer with nanofluid and twisted-tape inserts in tubeshave became widely used. scholars have researched: the systems of nanofluid, thestability, the thermal conductivity of nanofluid, the mechanism of nanofluid,measurement and factors of nanofluid viscosity. However, further research needs toaddress the surface heat transfer characteristics of nanofluid, so we use theoreticalanalysis and experimental study to study heat transfer characteristics and flowcharacteristics of nanofluid in twisted-tape inserts in tubes. Firstly, Use theoreticalanalysis to study on factor of heat transfer enhancement. Then study on therelationship of nanofluid stability and dispersant, Prepare the nanofluid of beststability, and measure its thermal conductivity. In order to study the heat transfercharacteristics of nanofluid in twisted-tape inserts in tubes, the heat transferexperimental system are designed and built, in the range of2000~7000of theReynolds number, respectively for the nanofluid Cu-water in the mass fraction of0.1%,0.3%,0.5%heat transfer characteristics of twisted-tape inserts in tubes. Theresults of experiments show that the friction factor decreased as the Reynolds numberincreased. The friction factor of the nanofluid was higher than the friction factor ofwater. The friction factor decreased as the quality score decreased,The friction factorof twisted tape insert pipe was higher than the friction factor of plain tube, and thefriction factor decreased as the twist ratio increased; The Nusselt number increasedwith the Reynolds number; The friction factor of the Fe2O3-water, Al2O3-water andCu-water nanofluid were close to each other. The Nusselt number of the nanofluidincreased with concentrations of nanoparticles; the Nusselt number of nanofluid ishigher than the Nusselt number of water. the Nusselt number of twisted tape insertpipe was higher than the plain tube, and the Nusselt number decreased as the twistratio increased. The Nusselt number of Cu-water nanofluid is higher then theFe2O3-water and Al2O3-water nanofluid.The enhancement with Cu-water nanofluid of 0.5%mass fraction for twist ratio of3.5and twist ratio of5.5is2.29and2.14respectively.