Steady-State and Frequency Response of a Thin-Film Heat Flux Gauge

Abstract

A new and simpler design of thin-lm heat ux gauge has been developed for use in high-heat-ux environments. Heat ux gauges of the same design were fabricated on three different substrates and tested. The heat ux gauge comprises a thermopile and a thermocouple junction, which measures the surface temperature. The thermopile has 40 pairs of S-type thermocouples and is covered by two thermal resistance layers. Calibration and testing of these gauges were rst carried out in an arc-lamp calibration facility. Sensitivity of the gauge was discussed in terms of the relative conductivity and surface temperature. The heat ux calculated from the gauge output was in good agreement with the precalibrated standard sensor. The steady-state and the transient response characteristics of the heat ux gauge were also investigated using a carbon dioxide pulse laser as a heat source. The dynamic frequency response was evaluated in terms of the nondimensional amplitude ratio with respect to the frequency spectrum of a chopped laser beam. The frequency response of the gauge was determined to be about 3 kHz. The temperature pro les in the thin-lm heat ux gauge were obtained numerically in steady-state conditions using FLUENT and compared with the experimental results.

Development of thin film heat flux sensor based on transparent conductive oxide thermopile with antireflective coating

“…The time constant is an indicator of the steady-state performance, but it does not explain the transient behavior (Cho et al , 1997) of the thin film HFS that can be evaluated in the dynamic test platform. To determine the thin film HFS frequency response function with this setup, time-series data for the infrared detector and the thin film HFS were acquired for square waves frequencies ranging from 120 Hz to 180 Hz.…”

Design and Fabrication of a Thick Film Heat Flux Sensor for Ultra-High Temperature Environment

“…Christopher reported a thin film heat flux sensor that consisted of a series of Pt/Rh thermocouples based on different substrates. Despite its high response frequency (3 kHz), it exhibited low sensitivity [13]. Theophilos S and his team developed a heat flux sensor, using thermal spraying technology, and realized heat flux test at 100 • C [14].…”

“…Moreover, the fabrication process of the heat flux sensors mentioned above are complicated and expensive. Thick film sensors have the same advantages as thin film sensors, such as lower impact on the test environment and shorter response times [13], [16]. More importantly, the thickness of the thick film sensors is 10 times or more than that of thin film sensors; hence, thick film sensors have better durability at ultra-high temperatures and are more suitable for use in harsh environments.…”

Thin Film Heat Flux Sensor Development for Ceramic Matrix Composite (CMC) Systems

“…For an example of the performance of such a sensor, a 40-pair thermocouple thin-film heat flux gauge was demonstrated in an arc-lamp calibration facility with sensitivity of 1.2 V·(W·cm-2 ) -1 and a dynamic frequency response of 3 kHz for temperatures on the surface of the sensors of up to 800 °C (Ref. 7).…”