A design of experimental apparatus for studying coupled heat and moisture transfer in soils at high-temperature conditions

摘要

The objective of this paper is to present a design of an experimental apparatus for studying coupled heat and moisture transport phenomena in soils at high temperatures up to 90 degrees C and to present some preliminary testing results from the apparatus for understanding the extent of its measurement uncertainties. A soil cell was designed and constructed for enclosing a vertical soil column for experimental studies of one-dimensional heat and moisture transfer in the soil column. The design of the experimental apparatus was realized based on the worst condition of achieving one-dimensional heat flow within a soil cell filled with dry soil. The soil cell, which is of cylindrical shape and contains five thermo-time domain reflectometry (T-TDR) probes, was sandwiched between a hot plate on the top and a cold plate at the bottom for studying coupled heat and moisture transfer in soils. The existence of one-dimensional heat flow from the top to the bottom of the soil column can be indicated by two conditions. In an ideal steady-state condition, first, the amounts of inflow and outflow rates of heat transfer at the top and bottom of the soil column should be the same, and secondly, the heat flux distribution at any cross-section of the soil column should be uniform. In the present design, these conditions were met within +/- 5% of their variations, as a design criterion. With respect to the design criterion, the general integrity and reliability of the design models were numerically assessed using COMSOL, based on realistic geometries and boundary conditions. Once the apparatus was built, a preliminary test of the apparatus was performed to check the existence of one-dimensional heat flow through the soil column in the soil cell.