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A field study on the application of distributed temperature sensing technology in thermal response tests for borehole heat exchangers
摘要： Although the enhanced thermal response test (ETRT) method has been used to determine the distribution of ground temperatures and effective thermal conductivities, there are a number of obstacles which limit the wide application of this technology in the discipline of geoengineering. In this literature, four aspects of ETRT technology were investigated: (a) acquisition of ground temperature, (b) installation of the heat exchange tubes, (c) optimization of the monitoring positions, and (d) the difference in thermal conductivity obtained by the ETRT and numerical simulation. To investigate these issues, a field trial was carried out in Heze, Shandong Province, China, and the corresponding numerical models were built. The results demonstrate that: (i) the conventional methods that infer undisturbed ground temperature using water in tubes have large errors, whereas the distributed temperature sensing (DTS) technique enables the measurement of precise temperature profiles; (ii) the thermal conductivity measured using double U-tubes reflects the soil thermal property more accurately than that for a single U-tube; (iii) it is more reasonable to install optical fibers outside the U-tube sidewall than inside the observation tube; and (iv) it is essential to quantitatively consider various interface thermal impedance when estimating ground thermal conductivities using numerical simulation.
关键词： Fiber optic sensor,Distributed temperature sensing (DTS),Ground-coupled heat pump (GCHP),Thermal conductivity,Thermal response test (TRT)
更新于2025-09-23 15:21:01
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Modeling of Quench Behavior of YBa<formula><tex>$_{2}$</tex></formula>Cu<formula><tex>$_{3}$</tex></formula>O<formula><tex>$_{7-\delta}$</tex></formula> Pancake Magnets and Distributed Temperature Sensing-based Quench Detection for Operating Temperature 30 K - 77 K
摘要： A two-dimensional/three-dimensional (2-D/3-D) mixed electrothermal model is proposed for the simulation of quench behavior of high-temperature superconducting (HTS) pancake magnets, where a 2-D electrothermal model is proposed to simulate the YBa2 Cu3 O7 -δ (YBCO) subcoil and is coupled with the remaining parts of the YBCO magnet, which are treated as 3-D homogeneous coils. For operating temperature from 30 to 77 K, the quench behavior of four YBCO pancake coils (two Kapton-insulated coils and two TiO2 -insulated coils) are simulated. Thermal equilibrium states are found for both Kapton- and TiO2 -insulated coils. The thermal conductivity of insulating materials (Kapton, TiO2 ) significantly affects the equilibrium temperature profiles (ETPs) and the minimum quench energy (MQE), especially for relatively high operating temperature (e.g., 65–77 K). The distributed-temperature-sensing-based (DTS-based) quench detection criterion can be established on ETPs. The effect of the thickness of insulating materials on ETPs and MQEs is relatively weak, especially under relatively low operating temperature. The key parameters of ETP-based quench detection criterion, such as the reference temperature, the peak temperature, and the minimum normal zone size, are obtained for the operating temperature from 30 to 77 K.
关键词： quench detection criterion,Distributed temperature sensing (DTS),high-temperature superconducting (HTS) magnet,quench simulation,minimum quench energy (MQE)
更新于2025-09-10 09:29:36