Use of a fiber optic distributed temperature sensing system for thermal response testing of ground-coupled heat exchangers

This paper reports on the use of a fiber optic distributed temperature sensing system to spatially resolve the temperatures along the entire length of a U-tube within a vertical bore geothermal well. The fiber optic probe inside the U-tube provides spatial temperature data at a 2-m resolution throughout the duration of a TRT. The spatial temperature data within the U-tubes provided by a fiber optic probe offers the potential to determine other characteristics of a test bore, such as ground properties as a function of depth, which will enable much more accurate ground heat exchanger models in the future. An added outcome of this technique is a direct means to observe stratification of fluid temperatures which is another indicator of differences in ground properties that may occur along the depth of a vertical bore.