6639

6190

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيبك

1390

چهارده، 98ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

علي اكبر عالم رجبي، احمدصابونچي

ارجمند مهرباني

5/2/91

محمدرضا سليم پور، مهدي نيلي احمدآبادي

1396/10/12

كتابنامه

مكانيك

مهندسي مكانيك

ID6190

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Effect of Electrohydrodynamic and Electrode Configurationon on Internal Natural Convective Heat Transfer Enhancement Pourya Alamdari P Alamdari@me iut ac ir Date of Submission 2012 01 02 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor A A Alemrajabi Rajabi@cc iut ac irAbstractHeat transfer enhancement leads to higher efficiency and lower weight and volume for heat exchangers Inother words achieving higher heat transfer rates results in better performance and lower size of thermaldevices for any specific thermal load All these mean a better economy less material and energy usage inthe process of manufacturing heat transfer or thermal devices Also smaller size of heat exchanger maycause lower pressure drop which in turn leads to lower energy consumption in the course of using it Heattransfer enhancement methods can be divided into two categories i e active and passive methods Usingelectrohydrodynamics or in short EHD is one of the active enhancement methods in heat transfer On theother hand EHD is an interdisciplinary branch of science which deals with effect of electric field on fluidflow Applying a high voltage between an electrode inside a tube and tube wall leads to a secondary flow inthe tube known as ionic wind or corona wind which disturbs the hydrodynamic and thermal boundarylayers and augments heat transfer in the tube EHD may be applied to enhance heat transfer in single phaseor multiple phases In the present research effect of electrohydrodynamics on natural convective heattransfer enhancement in a vertical tube under constant heat flux on its wall has been investigatedexperimentally The working fluid was air Electric field was applied between electrode wire s and the tubewall The electrodes were arranged in one two or four wires which were parallel to the tube axis Theapplied electric voltage was varied between zero and 12 7 kV kilo Volts The heat flux on the outersurface of the tube wall was 300Watts per square meter Positive EHD was used Effects of electrode wirediameter electrodes arrangement and electric field variation on the natural convection heat transfer insidethe tube were investigated The experimental results obtained can be summarized as followings Increasing the applied voltage or corona current leads to increase in heat transfer coefficient other parameters kept constant The inception voltage i e the lowest voltage at which corona wind forms for a specific condition increases with increase in the electrode diameter At a fixed voltage higher heat transfer enhancement is observed for lower electrode diameter At a fixed corona current a higher voltage is needed for bigger electrode diameter A wider range of voltage is applicable for smaller electrode diameter hence a better control on the tube wall temperature is achievable The highest heat transfer enhancement occurred for the smallest electrode diameter under the highest applied voltage close to spark over voltage which made heat transfer 2 65 fold Increasing the number of electrodes from one to two and from two to four increases the heat transfer from the tube inner surface However increase in heat transfer from one to two electrodes is more than that of two to four electrodes The Nusselt number for one two and four electrodes were 2 65 3 10 and 3 45 fold the Nusslt number for the case of no EHD The energy consumption for the case of one electrode did not vary considerably for different electrode diameters However energy consumption decreases as the number of electrodes increases Keywords Corona wind EHD Heat transfer Enhancement Tube Wire electrode

علي اكبر عالم رجبي، احمدصابونچي

ارجمند مهرباني

محمدرضا سليم پور، مهدي نيلي احمدآبادي