Estimation of Vadose Zone Water Flux from Multi‐Functional Heat Pulse Probe Measurements

Abstract

cluding empirical and tracer methods, were presented by Tyler et al. (1999) and Flint et al. (2002). A major A small multi-functional heat pulse probe (MFHPP) was applied advantage of the MFHPP technique is that the water to further develop measurement methodologies to improve on water flux estimations for unsaturated soils. The temperature responses of flux can be estimated indirectly from heat transport by four thermistors surrounding a central heater in a 2.7-cm diam. probe convection, without the need for either soil water matric were analyzed by the heat transport equation to estimate thermal head or hydraulic conductivity measurements. properties and convective heat flow. Volumetric heat capacity, water Temperature measurements have been used to meacontent, and thermal diffusivity were estimated from the horizontally sure water fluxes in other fields. For example, steady placed thermistors, neglecting the convective flow effects in the transstate measured temperature gradients in bore holes were verse direction, whereas the water flux density was estimated from used to estimate vertical water flow rates in groundwater, the temperature responses to the vertically placed thermistors. A using the analytical solution of Bredehoeft and Papadoparameter optimization technique was employed to fit the most likely pulos (1965), with minimum flow rates of about 30 cm parameters to the relevant analytical solutions. Falling head and multiyr Ϫ1 using thermistors with a practical precision of about step outflow experiments yielded independently obtained water flux measurements. Results showed that the estimated volumetric water 0.01ЊC (Sorey, 1971). Using time-series measurements, content corresponded well with independent gravimetric measure-thermal signatures in shallow estuarine sediments have ments with a RMSE of 0.0056 m 3 m Ϫ3 , across a wide range of water been successfully used to estimate changes in nutrientfluxes smaller than 0.5 m d Ϫ1. Thermal diffusivity values as obtained contaminated ground water recharge rates toward coastal with the MFHHP also agreed well with independently measured therwaters (Land and Paull, 2001) and to estimate percolamal diffusivity values, for water flux density values smaller than 2 m tion rates in deep vadose zone environments (Constantz d Ϫ1. For saturated conditions, the estimated water fluxes from the et al., 2003). Early application of the heat pulse tech-MFHPP measurements were accurate in the range between 0.056 and nique to estimate water flow originates in the plant 27.0 m d Ϫ1 , with a R of 0.995 and RSME of 0.0952 log(m d Ϫ1) (0.52 m science literature, where advective transport of heat by d Ϫ1). For unsaturated flow, MFHHP estimations significantly overestiwater was used to indirectly estimate sap flow rates in mated water flux density for flux values smaller than 0.10 m d Ϫ1. Within these limitations, we conclude that MFHPP methodologies trees (Marshall, 1958), mostly measuring flow magnitudes are now available, making possible simultaneous estimation of thermal of 1 ...

In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

“…TPHPS have been used to measure the advective liquid heat flux in mineral soils [Mori et al, 2005;Ochsner et al, 2005;Ren et al, 2000] but have not, to our knowledge, been previously used in peat soils.…”

Experimental comparison of thermal and solute dispersion under one‐dimensional water flow in saturated soils

“…The experimentally derived Equation determined in this study, however, conflicts with Equation , which was deduced theoretically by de Marsily () and showed a linear relation between the thermal dispersion coefficient and water flux density, and with that found by Rau et al (), which showed a square relation between two parameters. Mori et al () concluded that thermal dispersion was almost independent of J w for a Tottori Dune sand. Compared to the studies mentioned above for which heat dispersion was determined theoretically, indirectly or on an ideal porous media (e.g., Tottori Dune sand), the current study acquired the heat dispersion coefficient experimentally using natural soils with a non‐uniform particle‐size distribution and focused on relatively small water flow velocities.…”

“…Ren, Noborio, and Horton () combined heat‐pulse with TDR technology to develop a thermo–time domain reflectometry (thermo–TDR) probe, which can estimate simultaneously soil thermal properties with a heat‐pulse probe and soil hydraulic and solute transport model parameters with TDR technology under the same measurement volume. Thus, thermo–TDR allows simultaneous analysis of the nature of coupled flow, heat and solute transport in soil (Mori et al, ; Mortensen, Hopmans, Mori, & Simunek, ), which makes it possible to explore the relation between thermal and solute dispersion. Our previous study showed experimentally that thermal dispersion occurred in water‐saturated soils with one‐dimensional water flow and fluxes in the range of 1.2 to 21.6 cm hour −1 (Lu, Ren, & Gong, ), which established an experimental basis for further comparison of thermal and solute dispersion.…”

Predictions of Effective Thermal Conductivity of Complex Materials

“…11 Modified three-phase unit cell based on the lumped parameter model [35] and its decomposition into serial and parallel layers (I-III) of thermal resistors sensitive to contacts. As the microscopy instruments and the observation technologies are also well developed now, the image mapping has become a highly powerful tool for approaching the real structures in more geometric details such as the element shapes, orientations and connections, on the materials properties [84,85]. Better reconstruction processes have been used to generate two-phase [86,87] and multi-phase [88,89] random structures of porous materials based on the digital micro-tomographic information and statistical correlation functions.…”