بررسي تجربي انتقال حرارت جريان نانوسيال در لوله u-شكل موجي

چكيده انگليسي :

Experimental Study on Heat Transfer for Nano Fluids Flowing in U typeWavy Tubes Mohsen Alaeian m alaian@me iut ac ir 2011 9 19 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Ahmad sedaghat sedaghat@cc iut ac ir Abstract In general the enhancement techniques are divided into two groups active and passive techniques Theactive techniques require external forces e g electric field acoustic surface vibration The passivetechniques require special surface geometries or fluid additives Both techniques have been used forimproving heat transfer in heat exchangers In this work an experimental study is carried out to investigatethe effect of adding multi wall nanotubes to the Heat Transfer oil HT B oil on flow heat transfer andpressure drop characteristics Measurements of heat transfer for nanofuil flowing in u type wavyconfiguration on constant wall temperature boundary condition are presented The inner diameters of the testcopper tubes d are 15 1mm with dimensionless spacer length L d 4 375 between sequence u bends whereas The effect of nanoparticles concentration and the dimensionless curvature radius 2R d and numberof sequence u bends on the heat transfer was investigated in the range of the laminar regime Reynoldsnumber from about 100 to 2000 and for the dimensionless pipe curvature radiuses 2R d 2 375 4 0625 7 1875 and 9 25 in n 8 and for number of sequence u bends n 4 8 and 12 in 2R d 2 375 The testresults indicated enhancement of heat transfer with increasing of nanoparticles concentrations and decreasingdimensionless curvature radius and increasing number of sequence u bends The experiments are done forpure HT B oil and nanofluid flow inside U type wavy tubes To reach constant water temperature entire testsection is surrounded by saturated vapor Heat Transfer oil HT B oil and MWCNT HT B Oil nanofluidswith weight concentrations of 0 1 0 2 and 0 4 are considered as the working fluids The Rheologicalcharacteristics of nanofluids including density thermal conductivity viscosity and specific heat are measuredexperimentally Based on these measurements some correlations are proposed to predict the rheologicalproperties of nanofluids with different weight concentrations The results of the experimental measurementsshowed that adding nanoparticles to the base fluid would lead to an increase in density thermal conductivityand viscosity of the nanofluid and will decrease specific heat of the base liquid The results obtained forconvective heat transfer of flow inside U type wavy tubes indicated that by decreasing dimensionlesscurvature ratio 2R d the convective heat transfer coefficient is increased For 0 4 weight concentrationand dimensionless curvature ratio at 2 375 this enhancement observed 42 The applied range of Reynoldsnumber results indicated that for U type wavy tube the addition of nanoparticles to the base fluid augmentedheat transfer remarkably This augmentation relate to pure oil was about 51 at maximum Also theincreasing at number of U bend leads to enhancement of heat transfer coefficient In addition flow pressuredrop results showed that for U type wavy tube by adding nanotubes to the HT B oil the flow pressure dropincreases This was for 0 4 weight concentration in 2R d 2 375 about 180 at Re 136 With Having theexperimental data for heat transfer and pressure drop of flow two correlations are derived for predicting theNusselt number and pressure drop ratio of nanofluid flow for U type wavy tube Keywords convective heat transfer nanofluid U type wavy tube U bend enhancement

علاييان، محسن

بررسي تجربي انتقال حرارت جريان نانوسيال در لوله u-شكل موجي

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