Experimental model of a horizontal geothermal exchange system

We plan to evaluate the response of a near-surface horizontal geothermal exchange system improved with soil amendments. Soil amendments increase the thermal conductivity of background soils and therefore facilitate the transfer of heat from the thermal exchange pipe to the soil formation. During testing, we will be using distributed temperature sensing (DTS) arrays to monitoring the heat transfer response by heat flow from the thermal exchange pipe. We will measure the circumferential temperature field around the thermal exchange pipe at radial distances of 0.375 m and 0.75 m at 30-degree separations.

The model will be built on a 3 m by 3 m by 3 m soil pit, where 1.5 m of the thermal exchange pipe will be tested with background soil, and the other 1.5 m of the thermal exchange pipe will be tested with the amended soils. We will monitor the heat load and then the recovery of the system. Numerical models indicate that the testing will be a month-long. Additionally, to the temperature of the field, we will measure the flow in the geothermal exchange pipe and changes in the soil moisture during testing. The use of DTS will allow us having a density of measurements no afforded with other measurement systems. In this way, we will be able to calibrate numerical models that will include heterogeneity in the material and the heat transfer process and assess the response of amended soils in the design of more efficient geothermal exchange systems.