COMPARISON OF TECHNIQUES FOR EXTRACTING SOIL THERMAL-PROPERTIES FROM DUAL-PROBE HEAT-PULSE DATA

Temperature-by-time data obtained using a dual-probe heat-pulse device can be analyzed using two different approaches to determine the soil thermal diffusivity, volumetric heat capacity and thermal conductivity. One approach, referred to as the single-point method, is based on accurate identification of the peak in the temperature-by-time measurements, The second approach involves a nonlinear model fit of the appropriate temperature model to the temperature-by-time data, In this paper, we analyze dual-probe heat-pulse data and show how the soil thermal properties determined using these two approaches compare, The single-point method is easy to apply, but results are sensitive to choice of the peak value, which can be difficult to identify if the data are sparse and contain noise. The nonlinear model fit (Marquardt method) copes better with broad, fiat peaks and sparse, noisy data, Soil thermal properties obtained using either approach should be checked by comparing the fitted model with the measured temperature-by-time data. By doing so, one can quickly determine the validity of the results.