A numerical study on the influence of the insulation layer of the hot disk sensor on the thermal conductivity measuring accuracy has been conducted. It is found that the influences of the thermal contact resistance and the insulating layer could be excluded in the transient plane source method. Both the kapton5501 and the mica5082 sensor could measure stainless steel and ceramic with a deviation less than 3% while the deviation increases to 54.2% of silica aerogel because of the large heat loss proportion through the mica5082 sensor side. The simulation proved that the heat loss through sensor side and accuracy could be improved by increasing the radius of the sensor.

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Abstract:In this paper, the Diffusion Limited Cluster Aggregation (DLCA) method is employed to reconstruct the three-dimensional network of silica aerogel. Then, simulation of nitrogen adsorption at 77 K in silica aerogel is conducted by the Grand Canonical Monte Carlo (GCMC) method. To reduce the computational cost and guarantee accuracy, a continuous-discrete hybrid potential model, as well as an adsorbed layer thickness estimation method, is employed. Four different structures are generated to investigate impacts of specific surface area and porosity on adsorptive capacity. Good agreement with experimental results is found over a wide range of relative pressures, which proves the validity of the model. Specific surface area and porosity mainly affect nitrogen uptake under low pressure and high pressure, respectively.