بررسي تجربي و عددي انتقال حرارت جريان نانو سيال در لوله U -شكل

چكيده انگليسي :

Experimental and Numerical Studies on Heat Transfer of Nanofluid Flows Inside a U Bend Tube Mohammad Rasekh Rasekh2@gmail com May 2 2011 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors E Shirani and M A Akhavan EShirani@cc iut ac ir Akhavan@ut ac ir Abstract In this work experimental and numerical studies are carried out to investigate the effect of adding MultiWall Carbon Nano Tube MWCNT nano particles to the base oil on flow heat transfer and pressure dropcharacteristics The experiments are done for pure base oil and nano fluid with different mass percent flowinside U bend tubes Test sections were heated by an electrical heating coil wrapped around them to produceconstant heat flux condition Base oil sn 500 and MWCNT Base Oil nano fluids with weight fraction of0 23 0 46 and 0 69 are considered as the working fluids The rheological characteristics of nano fluidsincluding density thermal conductivity viscosity and specific heat are measured experimentally Based on these measurements some correlations are proposed to predict the rheological properties ofnano fluids with different weight fraction The results of the experimental measurements showed that addingnano particles to the base fluid would lead to an increase in density thermal conductivity and viscosity of thenano fluid and will decrease specific heat of the base liquid The results obtained for convective heat transferof flow inside U bend tubes indicated that by increasing heat flux and flow rate the convective heat transfercoefficient is increased Also it was observed that using nano fluid flow instead of base oil flow and applyingU bend tube will enhance the convective heat transfer In addition flow pressure drop results showed that by adding nano particles to the base oil the flowpressure drop increases Also by using the U bend tube instead of straight tube pressure drop of the flow isincreased considerably Having the experimental data for heat transfer and pressure drop of flow twocorrelations are derived for predicting the Nusselt number and friction factor of nano fluid flow U bend tube Furthermore the performance evaluation of the two enhanced heat transfer techniques studied in thisinvestigation showed that applying U bend tube instead of the straight tube is a more effective way toenhance the convective heat transfer compared to the second method which is using nano fluids instead of thebase liquid At the end of experimental section with the aid of work done it was determined that utilizingstabilizer elements Oleic Acid in oil MWCNT suspension is a more efficient way to increase heat transferrelative to the method of using nano fluid instead of base fluid Finally U bend tube were simulated numerically using Fluent software Fluid properties were extractedfrom equations derived in thermophysical properties section Boundary conditions were the same as that ofexperiment Eventually by utilizing these data using Fluent software and comparing the outputs of thenumerical simulation and experimental results it was observed that the results are in a good agreement Keywords Heat transfer pressure drop nano fluid constant heat flux U bend tube

راسخ، محمد

بررسي تجربي و عددي انتقال حرارت جريان نانو سيال در لوله U -شكل

افت فشار , شار حرارتي ثابت