A numerical study on the influence of insulating layer of the hot disk sensor on the thermal conductivity measuring accuracy

Abstract

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.

Analysis and improvement of the hot disk transient plane source method for low thermal conductivity materials

“…4(c, f). Increasing the radius of the whole sensor in general reduce the portion of heat loss and improve the accuracy, consistent with the conclusion by Zhang et al 20 This is mainly because, with fixed hKap, the amount of heat goes to the sample scale with the heated volume times the sensor area ~drH 2 = 2rH 3 while the heat loss to the Kapton insulating layers scales with the volume of the Kapton ~rH 2 and the heat loss to the air at the sensor edge only scale with the area of the side wall and is proportional to ~rH. Therefore, with the margin width of the Kapton fixed, the fraction of the heat loss to the sensor relative to the heat absorbed by the sample is reduced when rH increases for all low-α samples.…”

“…It also affects the size of reff by changing the contribution from the outermost ring heater. The effect of the Kapton margin is not captured by previous literatures 20. Increasing the margin width of the Kapton when it is still small increases the fraction of heat loss in the Kapton as well as reff and hence worsen the overprediction of kapp.…”

“…According to a standard 9 and early parameter analysis, 26 tmax should be limited in a range such Detailed information about the specific fitting and optimization procedure is rarely given in the literature, being typically either described simply as a least square method (often without specifying the fitting parameters) 20,27,28 or not clearly mentioned. 29 This details of this step were only mentioned in the early work on the TPS sensitivity and parameter estimation by Gustafsson and a few studies on a similar transient technique called dynamic plane source.…”

“…18,19 For aerogel samples, there is also a report on the discrepancy in the k result obtained with TPS measurements using different types of sensors insulated with mica and polyimide, where the former type showed a result 54% higher than the later for the same sample. 20 Error in the TPS measurement [20][21][22][23][24][25][26][27][28][29][30][31] comes from two sources: (1) uncertainty in the experimental data and the selection of time interval for analysis, and (2) deviation of the original idealized analytical heat transfer model 3,32 from the practical measurement scenario. Previous works on the former aspect focused on the sensitivity of the input parameters and the data fitting procedure based on the original analytical model, but could not explain the overestimation of k in TI materials.…”

Experimental Characterization of the Thermal Conductivity and Microstructure of Opacifier-Fiber-Aerogel Composite

“…For thermal conductivity measurement at high temperature, a Mica-insulated sensor is adopted to resist the high temperature. As investigated in our previous work, the plane source assumption will be questionable when measuring extremely low thermal conductivity materials using the Mica sensor [ 28 ]. The thermal conductivity of thermal insulation material measured by Mica sensor is overestimated to account for a portion of energy dissipating from the sensor’s side.…”