| Autor: |
Liu, Gang, Si, Bing C., Jiang, Ai X., Li, Bao G., Ren, Tu S., Hu, Ke L. |
| Zdroj: |
Soil Science Society of America Journal; March 2012, Vol. 76 Issue: 2 p370-374, 5p |
| Abstrakt: |
The dual probe (DP) method is a widely used method for determining the thermal conductivity (K), the specific heat capacity (c), and the thermal diffusivity (α) of soil, but this method overestimates c, particularly for dry soil. The objective of this study is to examine if the probe body and the thermal contact conductivity (H) lead to biased estimation of the thermal properties by using the DP method. We used the analytical solution for cylindrical heat sources with the finite Hvalue derived by Moench and Evans (1970). For an air‐dried sand sample with c= 756 J kg−1K−1, the experimental estimated cfrom the infinite line source (ILS) model for DP units, with the heater needles of 3.175 and 1.27 mm, is 953 J kg−1K−1and 904 J kg−1K−1, respectively. For 3.175‐ and 1.27‐mm heater needles, the cestimated by applying the ILS model to temperatures simulated using the Moench and Evans solution is 926 J kg−1K−1and 845 J kg−1K−1, respectively. Simulations suggest that both the existing of the finite probe body and Hmake contribution to the overestimation of cfrom the ILS model. The overestimation of cincreases with the increase in the radius of the heater needle and decreases with the increase of Hvalue. Using ILS could lead to substantial errors in the estimated cof dry soil. |
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