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چكيده انگليسي :

018 Experimental Study of the Effect of Heat Transfer Surface on Pool Boiling of TiO2 water Nanofluids EhsanDehghaniAshkezari Email ehsan dehghani@me iut ac ir Date of submission January 22 2014 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language Farsi Supervisor Mohammad Reza salimpour Email salimpour@cc iut ac irAbstractNanofluids have created considerable interest in recent times for their improved heat transfer capabilities With very small volume fraction of such particles the thermal conductivity and convective heat transfercapability of these suspensions are significantly enhanced Therefore in this present study one of convectionprocesses associated with the change in phase of a nanofluid which can occur at a solid liquid interface isinvestigated For this purpose boiling heat transfer characteristics of nanofluids with nano particlessuspended in water are studied using different volume concentrations of nano particles in a horizontal simpleflat and three grooved plates made from copper at ambient pressure The experiments are performed toexplore the effects of grooving heating surface on boiling heat transfer characteristics of nanofluids Twodifferent concentrations of 0 2 and 0 4 by volume of TiO 2 dispersed with water are prepared and theexperiments are performed in simple flat quadrangular grooved circular grooved and triangulate groovedheating surfaces Logarithmic diagram of heat flux passing through heating surface and boiling heat transfercoefficient are drawn in terms of superheat degree and heat flux respectively Also boiling heat transfercoefficients of nanofluid are compared with those of pure water in each of heating surfaces It has been observed that these nanofluids have poor heat transfer performance compared to pure water ineach of heating surfaces With increase in volume concentration of nano particles the heat transfercoefficient decreases and while grooving heat transfer surface enhances heat transfer coefficient of fluid Thetest results exhibit in each heat flux the triangulate grooved heating surface has the maximum heat transfercoefficient and heat transfer coefficient in circular grooved heating surface is larger than the heat transfercoefficient in quadrangular grooved heating surface for pure water and nanofluid in each volumeconcentration The average of increment associated with heat transfer coefficient in the boiling pure waterand nanofluid by volume concentrations of 0 2 and 0 4 in the quadrangular grooved heating surfaceare 34 79 34 15 and 28 33 respectively The average of relative increase of heat transfercoefficient is improved in the boiling pure water and nanofluid by volume concentrations of 0 2 and 0 4 in the circular grooved heating surface 50 58 40 85 and 34 68 respectively The average ofrelative increase associated with heat transfer coefficient in the boiling pure water and nanofluid by volumeconcentrations of 0 2 and 0 4 in the triangulate grooved heating surface is enhanced to 50 58 40 85 and 34 68 respectively Heating surface contact area with boiling fluid is calculated by SolidWork software The contact area of flat quadrangular grooved circular grooved and triangulate groovedare shown as 1590 43 mm2 3449 29 mm2 2499 70 mm2 and 3542 02 mm2 respectively From the testresults It is concluded that the increment of heating surface contact area is not only reason of increasingheat transfer coefficient in grooved heating surface Because the triangulate grooved heating surface has themaximum contact area and circular grooved heating surface area is larger than quadrangular grooved heatingsurface area The experiments confirm that the boiling heat transfer characteristics of TiO2 water nanofluidsare strengthen by using grooved heating surface Keywords Nanofluids Pool Boiling Grooved heating surface Contact area

دهقاني اشكذري، احسان

بررسي تجربي تاثير سطوح انتقال حرارت بر جوشش استخري نانو سيال آب- اكسيد تيتانيوم

جوشش استخري , سطوح گرمايش شياردار , مساحت تماس