مطالعه ي پارامتري جريان و انتقال حرارت جابجايي آزاد حول يك استوانه ي داغ افقي درون كانال عمودي با استفاده از تكنيك PIV

چكيده انگليسي :

Parametric Study of Free Convective Flow and Heat Transfer around a Horizontal Heated Circular Cylinder Inside a Vertical Channel using PIV Technique Alireza Ansari alireza ansari@me iut ac ir Date of Submission 2016 01 17 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Reza Tavakoli mrtavak@cc iut ac ir Mehdi Nili Ahmadabadi m nili@cc iut ac irAbstract Free convection phenomenon from a heated circular cylinder is commonly seen in the industry For thiscase it can be noted to heat transfer from power transmission lines heat exchangers and heat transfer frompipes In this study free convective flow and heat transfer from a heated circular cylinder inside a channelusing PIV technique was investigated In fact by taking two vertically plates around the cylinder in thewater the free convective between the two plates is flowed For different channel s geometry the flow fieldpatterns and surface temperature of the cylinder s surface distribution are obtained and the aim is findingappropriate channel s geometry to increase heat transfer from the cylinder Geometric parameters of thestudy including water level channel width length and angle of channel plates for convergent channel divergent channel and convergent divergent channel Flow field pattern is obtained by PIV technique andthe cylinder surface temperature is measured by thermocouples In each case by changing the mentionedparameters flow rate at the top of the cylinder surface temperature of the cylinder total volume of fluidpassing through the channel the position of the vortex and uniform flow pattern within the channel isdiscussed A vortex formed alongside of the plume and rise to the free surface where it detached from theplume structure and moved along the free surface Vortex dynamics and the physical characteristics of theswaying and meandering motions appeared to be interdependent The relationship between the flow patternand the heat transfer characteristics at the cylinder surface is studied and the origin of the oscillationdiscussed Diagram of flow velocity from cylinder and the cylinder surface temperature versus time isplotted By choosing appropriate geometry for the channel flow around the cylinder and through thechannel is well formed and by increasing the flow velocity over the cylinder the surface temperature of thecylinder decreased At last the heat transfer coefficient and the Nusselt number for cylinder surface inchannels with suitable geometry are achieved and compared with the free convective flow from cylinderwithout channel The results indicate increase in heat transfer coefficient for the cylinder surrounded withchannel According to the results the appropriate geometry to increase the heat transfer is convergent divergent channel In this case comparing by the channel with vertical plates the Nusselt number and freeconvection heat transfer coefficient of the cylinder surface have increased 1 4 and in comparison withthe cylinder without channel they have increased 6 6 The results are compared with valid experimentalresults and good agreement was observed Keywords Free convective flow Heated circular cylinder Nusselt number PIV technique

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مطالعه ي پارامتري جريان و انتقال حرارت جابجايي آزاد حول يك استوانه ي داغ افقي درون كانال عمودي با استفاده از تكنيك PIV

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