9805

9049

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1393

هفده، 137ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

محمدرضا سليم پور

ابراهيم شيراني

94/1/29

احمد صابونچي، محمدرضا توكلي

1396/09/25

كتابنامه

مكانيك

مهندسي مكانيك

ID9049

متخلخل فشار بيبعد 2 P p uin نمادها يوناني P ويسكوزيته PEC معيار ارزيابي عملكرد kg m s چگالي 3 kg m عدد پرانتل Pr ويسكوزيته سينماتيكي عدد رينولدز Re m2 s مجموع فاصله لايهها s محيط متخلخل از ديواره m مجموع فاصله لايهها S محيط متخلخل از ديواره بيبعد S 2s H دما K T چكيده افزايش انتقال حرارت در تجهيزات انتقال حرارت ازجمله مبدلها حرارتي موضوعي است آه تاآنون به طور گسترده مورد مطالعه قرارگرفتهاست تكنيكها بيشمار برا افزايش انتقال حرارت در مبدلها حرارتي لولها وجود دارد يكي از اين تكنيكها استفاده از محيط متخلخل ميباشد محيطها متخلخل دارا سطح تماس بزرگي با سيالات ميباشند آه ميتواند موجب تقويت عمل انتقال حرارت شود درضمن ضريب انتقال حرارت هدايتي آن ها نيز معمولا از مقدار مربوط به سيال مورد مطالعه بيشتر است به اين ترتيب با نصب يك قطعه متخلخل از جنس رسانا حرارتي خوب ميتوان در ماده بهآاررفته در ساخت مبدل

173Convective Heat Transfer Analysis inside a Channel Filled with Porous Media Mehrab Ghorbani Mehrab ghorbani@me iut ac ir Date of Submission 2015 01 18 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Mohammad Reza Salimpour Salimpour@cc iut ac ir Abstract Due to the lack of energy sources augmentation of heat transfer in heat exchangers is an important subject Also increasing the heat transfer in systems that are related to the energy reduces the environment pollution Different ways were suggested for enhancing the heat transfer in heat exchangers among them convective heat transfer in systems including porous inserts attracts many researchers due to the wide applications of these systems in engineering processes and equipment like geothermal energy recovery air heaters drying processes electronics cooling solid matrix heat exchangers etc by using porous media the space and material needed for heat exchanger would be reduced In the present work laminar fully developed flow and convective heat transfer between two parallel plates of a conduit were simulated Effects of five parameters such as three geometrical and two inherent parameters of porous media were studied The parameters were thickness of porous media distances of porous media layers to the wall number of layers of porous media permeability of the porous media and ratio of effective porous media conductivity to pure fluid conductivity Simulation was done using FLUENT software Besides constant temperature boundary condition was used at the walls In modeling of the energy transport the local thermal equilibrium is assumed Comparing the results of the present study to the analytical solutions a reasonable agreement was observed At first a simple channel was modeled and compared with analytical solution and reasonable agreement was observed After that channels with porous media were simulated and It was found that the previously mentioned parameters had significant influence on fluid flow and heat transfer in certain conditions The results thoroughly document the dependence of the Nusselt number and pressure loss on several parameters of the problem All results are non dimensionalized To study the heat transfer and pressure drop due to the porous media two non dimensional numbers were used namely Nusselt number and pressure drop coefficient Two different effective porous media conductivity to pure fluid conductivity ratio 1 and 10 were considered in simulation and at each ratio different ternds for Nusselt number were reported This issue can be reasoned by this fact that at each conductivity ratio of unity hydrodynamics of problem is important while at conductivity ratio of 10 hydrodynamics and thermal considerations would affect the Nusselt number In order to consider the effects of porous media on heat transfer and pressure drop simultaneously a non dimensional number was introduced namely performance evaluation criteria PEC The results show that when the thermal conductivity and Darcy number of porous media are high adjoining two layers of porous media to the walls would result in the best performance and it would be better by increasing the thickness of porous media This is a practical case as woven screen materials show similar conditions Also it was observed that for thin layers with high permeability of porous media increasing the number of layers would reduce the heat transfer while for thick layers with low permeability of porous media increasing the number of layers would increase both heat transfer and pressure drop Keywords Heat transfer Porous media Convective heat transfer Performance evaluation criteria Fully developed fluid flow

محمدرضا سليم پور

ابراهيم شيراني

احمد صابونچي، محمدرضا توكلي