Modelling of heat transfer processes of laser heated nanoparticles with gas environment
The model of heat transfer of laser heated nanoparticles in the gas environment was developed for laser induced in-candescence (LII) signals interpretation. The model take into account the nanoparticles absorption of the laser energy in the Raleigh limit conditions, particle cooling by radiation, evaporation of the particles material and conduction heat transfer with the molecules of the bath gas. The known temperature dependences of the heat capacity and density of the soot and bulk iron were used for the calculations for carbon and iron nanoparticles. The particle diameters log-normal distribution function was applied to calculate the particle thermo radiation. On the base of the model developed the program code was created for mean particle diameter extraction from experimental incandescence signals. The results of nanoparticle sizing, obtained by LII, were compared with the electron microscopy data and a good agreement both in count median diameter and standard deviation were found.
В работе проведено моделирование процессов лазерного нагрева и последующего охлаждения наночастиц в газовой среде. Детально проанализирован процесс поглощения лазерной энергии наночастицами в пределе Рэлея с учетом временного и пространственного распределения энергии в лазерном пучке, а так же охлаждение при столкновениях наночастиц с молекулами окружающего газа в свободно-молекулярном режиме и потери энергии наночастицами в процессе их испарения и радиационного теплообмена. На основе развитой модели создано программное обеспечение для анализа и интерпретации полученных в эксперименте сигналов теплового излучения лазерно-нагретых наночастиц (лазерно-индуцированной инкандесценции) и определения их текущих размеров. Результаты работы могут быть применены для создания диагностического комплекса по мониторингу загрязнений окружающей среды и средств контроля при производстве нанопорошков.
наночастицы, теплообмен, лазерный нагрев, моделирование процессов
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