بهينه سازي خواص تشعشي لايه هاي نازك

چكيده انگليسي :

۶۶ Optimization of Thermal Radiative Properties of Thin Films Babak Baradaran Naghshineh b baradaran@me iut ac ir Date of Submission 2014 09 13 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Ahmad Saboonchi ahmadsab@cc iut ac irAbstract Thin film coatings have a very important role in semiconductor technologies optical devices spectralselective coatings and other Micro nano electromechanical applications Due to wave interference byadding a thin film coating to a surface radiative properties will be completely different Radiativeproperties of a thin film multilayer structure depends on many factors Material Thickness and Temperatureof layers are the most important factors In current project radiative properties of thin film multilayers arecalculated using electromagnetic methods and material and thickness of each layer are optimized for desiredapplications using Simulated Annealing and Genetic Algorithm in MATLAB software Passive cooling is one of the investigated applications If humidity is not too high the atmosphere willact as a heat sink in 8 13 m waveband which is called atmospheric window If energy transfer is limitedin this waveband by using an spectral selective coating cooling can be possible without any energyconsumption Applications are food and medicine storage roof cooling in dry climates and condensingatmospheric water Maximum Cooling Power is accessible by placing an object under bare sky at night Buta convective shield is required to reduce convective heat transfer to ambient and increase temperature drop Due to high Solar irradiance during day passive cooling can be very difficult under direct sunlight Preparing a proper convective shield for passive cooling during day is still an unsolved challenge inmaterial science Considering Cooling Power as objective function in Optimization 15 different thin filmmultilayer structures are introduced for passive cooling during day in this project Based on calculations asmall temperature drop about 2 3 C can be possible under direct sunlight by using some of introduced thinfilm multilayers Temperature drop at night can be increased up to 105 by using these structures 12 optimized thin film multilayers are also introduced for passive cooling at night Based oncalculations temperature drop can be increased up to 120 by using introduced structures Using a layer of KBr or NaF with hight solubility in water coated from both sides with thin films isintroduced for the first time as a very proper convective shield for passive cooling at night which will resultin 123 increase in temperature drop Preparing a suitable Heat Mirror is another investigated application in this project Heat Mirror is anspecial kind of glass with high Transmittance in visible range and high Reflectance in infra red region toprevent radiative heat transfer with ambient and decrease heat loss as much as possible 6 optimized thinfilm multilayer structures are introduced to modify radiative properties of a single layer of SiO2 for use as aHeat Mirror Reflectance of SiO2 in infra red region can be increased up to 415 by using proper thin filmcoatings BaTiO3 is also introduced as a proper Heat Mirror for the first time 20 optimized structures are also introduced with maximum absorptance in solar region Such highabsorptance structures can be used in Solar Collectors and Solar Cells Simillar structures are alsointroduced with maximum transmittance and maximum reflectance in solar region Keywords Heat Transfer Thin Films Nano scale Radiative Heat Transfer Thermal RadiativeProperties Passive Cooling Heat Mirrors Optimization

برادران نقشينه، بابك

بهينه سازي خواص تشعشي لايه هاي نازك

انتقال حرارت , انتقال حرارات تشعشي در ابعاد نانو , خنك كاري , آينه هاي حرارتي