6053

5662

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1389

يازده،86ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

علي اكبر عالم رجبي

ارجمند مهرباني

7/4/90

احمد صابونچي، احمد صداقت

مهندسي مكانيك

ID5662

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Experimental Investigation of Electrohydrodynamic Effect on Convective Heat Transfer Enhancement in a Pipe by Using Helical Electrode Seyed Mojtaba Mirhosseini m mirhosseini@me iut ac ir May 22th 2011 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor A A Alemrajabi Assoc Prof Rajabi@cc iut ac ir AbstractA corona is a visible luminous emission that occurs in the vicinity of sharp edges where the electric field isintense This phenomenon is associated with gas ionization and acceleration of ions in strong electric fields dragging the gas particles and generating a secondary flow known as corona wind Corona wind may beemployed as an active enhancement technique for heat transfer The effect of corona wind is entitledelectrohydrodynamic EHD that may significantly improve convective heat transfer coefficient in thedeveloping and developed regions of a tube An experimental research was conducted to investigate the level of heat transfer enhancement in thedeveloping region of a circular tube by helical electrode This wire electrode charged with a high negativevoltage was coiled around a non conductive circular cylinder The wire was contacted to a high voltagesupply The study focused on the laminar to lower range of turbulent flows with Reynolds number andvoltage ranging from 1500 to 10 000 and 0 to 17 1 kV respectively Also three different constant heat fluxeswere applied to the outer surface of the tube Maximum enhancement occurred between Re 2500 and 4000 Energy consumption of this enhancement technique is very low Also in this study the effect of electrode geometry such as diameter and pitch of the coiled wire electrodewere investigated and the optimum values of mentioned parameters were specified The results can besummarized as follow 1 By increasing the applied voltage and current convective heat transfer is increased 2 By increasing the applied heat flux the convective heat transfer is increased with or without applying EHD 3 EHD is more effective at lower heat fluxes 4 Also EHD is more effective at lower Reynolds numbers 5 The higher the diameter of the coiled wire electrode the higher the inception voltage is Also at a constant applied voltage it is observed that the smaller electrode diameter leads to larger enhancement 6 At a constant applied voltage Power consumption by EHD is inversely proportional to the electrode diameter 7 In general an increase in the gamut of the coiled wire electrode leads to a decrease in the average convective heat transfer KeyWords Corona wind EHD Heat transfer Enhancement Tube Helical electrode Geometry

علي اكبر عالم رجبي

ارجمند مهرباني

احمد صابونچي، احمد صداقت