Errors Analysis Of Heat Pulse Probe Methods: Experiments and Simulations

Abstract

The heat pulse probe (HPP) method can be used to measure specific heat capacity (c), thermal conductivity (λ), and water content of soil; however, many factors are believed to contribute to measurement errors in both λ and c from the HPP method. The objective of this study was to examine if contact resistance, heat‐driven flow, temperature‐dependent thermal properties, or epoxy fillings affect the estimated soil thermal properties and water content from the HPP method. Heat pulse experiments were conducted on oven‐dry sand, water‐saturated sand, sand saturated with agar‐stabilized water, and coarse snow (large grain size). The results showed that for the sand and coarse snow, the thermal contact resistance did not contribute to the overestimation of heat capacity. There was little difference in measured water contents between sand saturated with water and sand saturated with agar‐stabilized water, suggesting no obvious heat‐driven flow under saturated conditions. Compared with an 8‐s heat pulse with a power strength (q′) >80 W m−1, a long heat pulse of duration 60 s and q′ < 6 W m−1 reduced the overestimation of soil c and water content (θw) on oven‐dry sands. Both temperature‐dependent soil thermal properties and epoxy filling inside the heater needle contributed to the overestimation of c and θw.