A Case Study of Field Thermal Response Test and Laboratory Test Based on Distributed Optical Fiber Temperature Sensor

Abstract

To design an efficient ground source heat pump (GSHP) system, it is important to accurately measure the thermophysical parameters of the geotechnical layer. In the current study, a borehole is tested in detail using a combined thermal response test system (CTRTS) based on a distributed optical fiber temperature sensor (DOFTS) and a laboratory test. Real-time monitoring of the stratum temperature according to depth and operation time and the geothermal profile and thermal conductivity of each stratum are obtained. The results show that the undisturbed ground temperature is 10.0 °C, and the formation temperature field within 130 m can be divided into variable temperature formation, constant temperature formation (9.13 °C), and warming formation (geothermal gradient is 3.0 °C/100 m). The comprehensive thermal conductivity of the region is 1.862 W/m·K. From top to bottom, the average thermal conductivity of silty clay, mudstone, argillaceous siltstone, and mudstone is 1.631 W/m·K, 1.888 W/m·K, 1.862 W/m·K, and 2.144 W/m·K, respectively. By comparing the measurement results, the accuracy and effectiveness of the CTRTS are verified. Therefore, it is recommended to use the thermal conductivity obtained by the CTRTS to optimize the design of the borehole heat exchanger (BHE). This study provides a case for establishing a standard distributed thermal response test (DTRT).

Calibration and Uncertainty Quantification for Single-Ended Raman-Based Distributed Temperature Sensing: Case Study in a 800 m Deep Coaxial Borehole Heat Exchanger

“…DTS offers interesting perspectives in BHE and GSHP applications and has gained interest in recent years, be it for monitoring, field tests (DTRTs), validation of heat transfer models, estimation of the geothermal gradient, evaluation of undisturbed temperature or thermal conductivity maps [19,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]47].…”

“…In the reviewed literature, application of the DTS technique to GSHP research first appears in the context of Distributed Thermal Response Testing (DTRT) [18][19][20][21]. DTRTs based on DTS is still a current topic of research and even seems to have regained interest in recent years [22][23][24][25][26][27][28].…”

Calibration and Uncertainty Quantification for Single-Ended Raman-Based Distributed Temperature Sensing: Case Study in a 800 m Deep Coaxial Borehole Heat Exchanger

“…DTS offers interesting perspectives in BHE and GSHP applications and has gained interest in recent years, be it for monitoring, field tests (DTRTs), validation of heat transfer models, estimation of the geothermal gradient, or evaluation of undisturbed temperature or thermal conductivity maps [ 21 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 33 , 34 , 35 , 36 , 37 , 41 , 42 , 43 , 44 , 54 ].…”

“…In the reviewed literature, application of the DTS technique to GSHP research first appears in the context of distributed thermal response testing (DTRT) [ 20 , 21 , 22 , 23 ]. DTRTs based on DTS is still a current topic of research and even seems to have regained interest in recent years [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”