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Semianalytical Solution for DualProbe HeatPulse Applications that Accounts for Probe Radius and Heat Capacity
 Author:
 Knight, John H., Kluitenberg, Gerard J., Kamai, Tamir, Hopmans, Jan W.
 Source:
 Vadose zone journal 2012 v.11 no.2 pp. 19761982
 ISSN:
 15391663
 Subject:
 heat, soil thermal properties, spatial distribution, temperature, vadose zone
 Abstract:
 The dualprobe heatpulse (DPHP) method is useful for measuring soil thermal properties. Measurements are made with a sensor that has two parallel cylindrical probes: one for introducing a pulse of heat into the soil (heater probe) and one for measuring change in temperature (temperature probe). We present a semianalytical solution that accounts for the finite radius and finite heat capacity of the heater and temperature probes. A closedform expression for the Laplace transform of the solution is obtained by considering the probes to be cylindrical perfect conductors. The Laplacedomain solution is inverted numerically. For the case where both probes have the same radius and heat capacity, we show that their finite properties have equal influence on the heatpulse signal received by the temperature probe. The finite radius of the probes causes the heatpulse signal to arrive earlier in time. This time shift increases in magnitude as the probe radius increases. The effect of the finite heat capacity of the probes depends on the ratio of the heat capacity of the probes (C0) and the heat capacity of the soil (C). Compared with the case where C0/C = 1, the magnitude of the heatpulse signal decreases (i.e., smaller change in temperature) and the maximum temperature rise occurs later when C0/C > 1. When C0/C < 1, the magnitude of the signal increases and the maximum temperature rise occurs earlier. The semianalytical solution is appropriate for use in DPHP applications where the ratio of probe radius (a0) and probe spacing (L) satisfies the condition that a0/L ≤ 0.11.
 Agid:
 310698

http://dx.doi.org/10.2136/vzj2011.0112