ساخت، مشخصه يابي و ارزيابي تجربي عملكرد حرارتي مواد تغييرفازدهنده ميكروكپسوله حاوي نانوذرات

چكيده انگليسي :

Abstract In the present study preparation and thermal characterization of themicroencapsulated lauric acid LA and paraffin Pa with a poly styrene shell was carriedout using an emulsion polymerization technique for the first time The optimization of themicroencapsulation process of the LA and Pa as phase change materials PCM wasinvestigated using response surface methodology RSM The quadratic polynomialregression model was applied for predicting microencapsulation ratio The maximumachieved value of microencapsulation ratio under the optimal conditions was 87 7 and91 64 for Pa and LA respectively The optimal independent variables using responsesurface methodology were PA styrene St mass ratio of 0 39 emulsifier SDS St massratio of 0 035 and the stirring rate of 1500 rpm in the microencapsulation process of PA For the microencapsulation process of LA the optimal variables determined LA St massratio of 0 42 SDS St mass ratio of 0 01 stirring rate of 1076 rpm and the temperature of55oC using RSM Under the optimal conditions the average diameter of Pa and LAmicrocapsules is about 18 3 m and 1 32 m respectively Thermogravimeric analysis TGA showed that thermal stability of microencapsulated samples are higher than that forpure LA and Pa samples The results showed that obtained microcapsules with themaximum microencapsulation ratio can be considered to have good potential for energystorage After determination of the optimal conditions the effect of presence of three kindsof nanoparticle of MgO TiO2 and graphite with mass ratios of 3 5 7 and 10 on thethermal properties of the Pa and LA microcapsules was investigated Themicroencapsulation ratio of LA increases with amount of MgO and TiO2 However themicroencapsulation ratio was reduced with increasing the mass ratio of nano graphite MgO and TiO2 nanoparticles were inlayed in paraffin microcapsules by surfacemodification The microencapsulation ratio of Pa decreased by increasing the mass ratio ofthese nanoparticles It could be due to the difference in the structure of Pa and LA Thediameter of the paraffin microcapsules with nanoparticles is larger than that of the LAmicrocapsules with similar nanoparticles The LA and Pa microcapsules with TiO2nanoparticles have the maximum microencapsulation ratio compared to other types ofnanoparticles Scanning electron microscopy SEM images showed that microcapsulesobtained containing TiO2 were spherical with smooth surface and narrow particle sizedistribution The thermal stability and thermal conductivity coefficient for the pure phasechange materials obtained microcapsules with and without nanoparticles wereinvestigated The thermal stability improved with increasing mass ratio of thenanoparticles no considerably Thermal conductivity of the microcapsules was increasedwith addition of nanoparticles The results show that LA and Pa microcapsules with TiO2nanoparticle have higher thermal stability than other nanoparticles Thermal performanceof the obtained samples was evaluated in a designed experimental setup The results showthat the slope of temperature time in heating curve of the LA samples is more than Pasamples It is verified by the higher thermal conductivity coefficient of LA samples Also the slope of heating curves of the LA microcapsules containing MgO TiO2 graphite andmicrocapsules without nanoparticle respectively increases in comparison to the slope ofheating curve of the pure LA due to higher thermal conductivity coefficient ofcorresponding samples The Pa and LA microcapsules with MgO nanoparticle have themost thermal conductivity coefficient and attain the highest temperature stability in theheating process According to the thermal conductivity enhancement of the microcapsulesin comparison with the pure samples the start of melting and solidification process wasconsiderably accelerated in the heating and cooling process respectively Keywords Phase Change Material Microencapsulation Polymerization Optimization Nanoparticles Thermal conductiv

سامي، سمانه

ساخت، مشخصه يابي و ارزيابي تجربي عملكرد حرارتي مواد تغييرفازدهنده ميكروكپسوله حاوي نانوذرات

ماده تغييرفازدهنده , ميكروكپسوله سازي , پليمريزاسيون , بهينه سازي , نانوذرات , ضريب هدايت حرارتي , عملكرد حرارتي