Large Column Setup for flow and heat transport experiments
The laboratory setup illustrated in Fig 1. can be used to study one-dimensional (1D) heat and solute tracer transport through a cylinder-shaped sample (length 1.5 m, inner diameter 0.29 m) at seepage velocities of va = 1 ‑ 50 m d‑1 and at temperatures of 5 – 70 °C.
Figure 1
Schematic experimental setup of the column. The refrigerated bath circulators serve as a hot and cold water storage. The volume flow is controlled by an eight-channel peristaltic pump. The red dots mark the positions of the Pt100 temperature sensors. The column can be installed in a vertical and horizontal configuration.
To enable an instant change between hot-water injection and cold-water injection, two refrigerated bath circulators (Witeg WCR-P22) are used. The two devices have an accuracy of ± 0.1 K. They can be used independently for heating and cooling and served here as cold and hot water tanks. An eight-channel peristaltic pump (Ismatec Ecoline) is used to control the volume flow into the column. A three-way valve is installed at each of the inflow tubes close to the column to allow tempering of the tubes without injection into the column. Furthermore, the three-way valves are used to inject a solute tracer.
A soil sample can be inserted in the acrylic glass column (Fig 2.).
Figure 2
Uniform inflow and outflow of the column is ensured by eight radially arranged inlets (CPC couplings) in the lid and the bottom of the column and by an inflow distributor consisting of a perforated plate with a distance of 4 cm after the lid.
A vertically movable perforated stabilization plate mounted on the lid prevented shifting of the sample during tilting of the column (Fig. 3). The column is thermally insulated by a 5-cm-thick layer of K‑Flex 25 (l = 0,034 W m-1 K-1) insulation. In addition, the inflow tubes are thermally insulated by a K‑Flex tube (wall thickness 10 mm). A tank at the end of the outflow tubes is installed to ensure the same pressure level at each outflow tube. A tank at the outflow is used to determine the volume flow through the column.
Figure 3
a) lid of the column with a movable perforated stabilization plate to prevent shifting of the sample during tilting of the column.
b) top view of the lid with dimensions. The bottom lid of the column is similar without the threaded bars and threads.
Further descriptions and results of the experiments can be found in the following publication:
Gossler, M. A., Bayer, P., Zosseder, K. (2019): Experimental investigation of thermal retardation and local thermal non-equilibrium effects on heat transport in highly permeable, porous aquifers, Journal of Hydrology. https://doi.org/10.1016/j.jhydrol.2019.124097