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.

本项研究旨在评估经土壤改良剂提升的近地表水平地热交换系统的响应。土壤改良剂可提升背景土壤的热导率，从而促进热量从地热交换管道向土壤层的传递。在测试过程中，我们将采用分布式温度传感（DTS）阵列，通过地热交换管道的热流来监测热量传递的响应。我们将测量地热交换管道周围在径向距离0.375米和0.75米处，以及每隔30度角的环向温度场。该模型将建立在3米×3米×3米的土壤坑中，其中1.5米的地面交换管道将与背景土壤进行测试，而剩余的1.5米地热交换管道将与改良土壤进行测试。我们将监测热负荷及系统的恢复情况。数值模型显示，测试将持续一个月。此外，除了现场温度测量外，我们还将测试期间地热交换管道中的流量变化和土壤水分的变化。DTS的使用将允许我们实现其他测量系统无法提供的测量密度。通过这种方式，我们将能够校准包括材料异质性和传热过程在内的数值模型，并评估改良土壤在更高效地热交换系统设计中的响应。