کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4994360 1458033 2017 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A thermal conductivity study of double-pore distributed powdered silica aerogels
ترجمه فارسی عنوان
یک بررسی هدایت حرارتی از آلیاژل های سیلیس پودر توزیع شده دو ذره است
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی جریان سیال و فرایندهای انتقال
چکیده انگلیسی
Powdered nanoporous silica aerogel is a typical double-pore distributed material. This paper develops a total effective thermal conductivity model that considers the coupling effect between different forms of heat transfer for the microstructure features of powdered silica aerogel by using an ideal structure with nanoporous spheres arranged in a spatially periodic structure. Performance of the developed model is compared to experimental results, with the effects of various parameters on thermal conductivity analyzed. The results show that the thermal conductivity of powdered silica aerogel decreased with decreasing gas pressure, and stabilized at its lowest value at pressures below 20 Pa. A turning point existed at approximately 103 Pa when looking at the logarithmic scale of gas pressure. The thermal conductivity decreased quite slowly with decreasing pressure when p > 103 Pa, but more quickly when gas pressure was lower than 103 Pa. The thermal conductivity reduced with increased specific surface area, but did not change with powder diameter D when the pressure was higher than 103 Pa. On the other hand, the thermal conductivity increased with increasing powder diameter D, but did not change with specific surface area when the pressure was less than 103 Pa. As the powder diameter D decreased, the lowest stable point of the thermal conductivity increased. The radiation heat transfer contribution was very small when the temperature was less than 400 K. With elevating temperature, the thermal conductivity of powdered silica aerogel distinctly increased. Thus, silica aerogel samples with large macro pores achieve greater thermal conductivity at elevated temperatures.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Heat and Mass Transfer - Volume 108, Part B, May 2017, Pages 1297-1304
نویسندگان
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