Dynamic characterization of Fiber Bragg Grating temperature sensors

Clemens Naumann, Tommaso Carlesi, Henning Otto, Christian Cierpka, Delphine Laboureur

    Research outputpeer-review

    Abstract

    To reliably characterize fast dynamic heat transfer mechanisms, fast-response temperature sensors are crucial, including knowledge about the temporal response. In this paper, the dynamic behavior of a Fiber Bragg Grating temperature sensor is investigated and compared to different types of fast-response thermocouples using two different experimental dynamic characterization methods. A temperature step is generated by either plunging the sensor into a fluid or exposing it to a fluid droplet at different temperatures. The step response is evaluated to determine the sensor response time. Calibration runs are performed for a silica-based 0.125 mm FBG sensor, as well as for 0.16 mm and 0.8 mm exposed tip and 0.25 mm sheathed tip type K thermocouples. Water, glycerin, oil and GaInSn were used to cover a broad range of applications regarding different thermal diffusivities and viscosities. The FBG sensor showed the shortest response times compared to the thermocouples, ranging from 60 ms in oil down to 3 ms in liquid metal, which is 20 % up to 70 % faster compared to a 0.25 mm sheathed tip type K thermocouple. Additional plunging calibration runs of the FBG sensor were performed in a ternary nitrate molten salt mixture (HITEC) to determine its overall and dynamic behavior in corrosive fluids at elevated temperatures. It turns out that the FBG sensor is not affected by the molten salt and shows similar response times to those measured in water. Regarding the characterization methods, both techniques show reproducible results, even though the droplet method is inapplicable for sensors with higher heat capacity or lower thermal conductivity than the calibration fluid. Furthermore, splashing effects for fluids with low viscosity reduce the reliability of the droplet method. The results also show that a dynamic characterization is indispensable for temperature measurements with high temporal resolution because the response time depends on the sensor size and the heat transfer coefficient between sensor and surrounding, which in turn depends on the sensor type, fluid properties and the flow parameters.

    Original languageEnglish
    Article number111222
    Number of pages10
    JournalExperimental Thermal and Fluid Science
    Volume156
    DOIs
    StatePublished - Jul 2024

    Funding

    The work has been partly carried out in the framework of the Short Training Program (STP) at the von Karman Institute for Fluid Dynamics. The authors like to thank the Electromagnetism and Telecommunication Department of the University of Mons for the in-house manufacturing of the Fiber Bragg Gratings and for providing the BaySpec (ANO/02) interrogator and the Sense 20/20 software for the use of optical fibers. Financial support from the German Research Foundation within the priority programme 2403 \u2019Carnot Batteries\u2019 under grant no. 525893212 is gratefully acknowledged. The work has been partly carried out in the framework of the Short Training Program (STP) at the von Karman Institute. The authors like to thank the Electromagnetism and Telecommunication Department of the University of Mons for the in-house manufacturing of the Fiber Bragg Gratings and for providing the BaySpec (ANO/02) interrogator and the Sense 20/20 software for the use of optical fibers. Financial support from the German research foundation within the priority programme 2403 \u2019Carnot Batteries\u2019 under grant no. 525893212 is gratefully acknowledged.

    FundersFunder number
    VKI - The Von Karman Institute for Fluid Dynamics
    Université de Mons ANO/02
    Deutsche Forschungsgemeinschaft525893212

      ASJC Scopus subject areas

      • General Chemical Engineering
      • Nuclear Energy and Engineering
      • Aerospace Engineering
      • Mechanical Engineering
      • Fluid Flow and Transfer Processes

      Cite this