Dynamic Calibration of a Thin-Film Heat-Flux Sensor in Time and Frequency Domains

Abstract

This paper mainly studies the model design of a thin-film heat-flux sensor (TFHFS), and focuses on the comparison of three dynamic calibration methods. The primary motivation for studying this came from the urgent need for heat-flux dynamic measurements in extreme environments, and the one-sidedness of the dynamic performance evaluation of the corresponding TFHFS. The dynamic theoretical model of the TFHFS was originally established on the principle of a temperature gradient on the basis of a thermal radiation boundary. Then, a novel TFHFS sensor was developed, which can be used at temperatures above 880 °C and has a high sensitivity of 2.0 × 10−5 mV/(W/m2). It can function stably for long durations under a heat-flux density of 3 MW/m2. The steady-state, transient, and frequency calibration of a TFHFS were compared to comprehensively analyze the dynamic characteristics of the TFHFS. The steady-state response time measured by the step excitation method was found to be 0.978 s. The QR decomposition method was applied to the steady-state response experimental model construction, and the fitting degree of a second-order transfer function model obtained was 98.61%. Secondly, the transient response time of the TFHFS was 0.31 ms based on the pulse-excitation method. The transient relationship between the surface temperature and the heat flux, and the pulse-width dependence of the TFHFS transient response time were established. Surprisingly, the response frequency of the TFHFS, about 3000 Hz, was efficiently tested using the frequency response function (FRF), which benefitted from the harmonic characteristics of a periodic square-wave excitation signal. Finally, a comprehensive evaluation of the dynamic performance of the TFHFS was realized.

Development and Performance Analysis of an Atomic Layer Thermopile Sensor for Composite Heat Flux Testing in an Explosive Environment

“…According to reference [7], the rise time of a high-brightness fireball's thermal radiation at the moment of initiation is approximately 40 µs, allowing the ALTP to theoretically detect the radiant heat flux in an explosion field. Figure 4b illustrates the TFHF's experimental results under varied laser pulse durations (0.3 ms to 3 ms) [17]. A reduction in pulse width results in the TFHF's potential output value decreasing from 0.05 V to 0.032 V, with a pronounced attenuation of amplitude.…”

High Temperature Heat Flux Sensor With ITO/In2O3 Thermopile for Extreme Environment Sensing

“…Among them, ITO-In2O3, as a transparent conductive oxide, has the advantages of high-temperature resistance, high output, and strong oxidation resistance in hightemperature environments, which can be used as a substitute for precious metal thermopiles 28 . The main materials for the thermal resistance layer are alumina 2,19 , silicon dioxide 19,20,[23][24][25]27,29 , YSZ 28 , etc. Li et al 2 fabricated an ITO-In2O3 thermoelectric stack thin film heat flux meter using magnetron sputtering method on a nickel alloy substrate, with a sensitivity of 61.93 uV/(kW/m 2 ) and a maximum operating temperature of 888 ℃.…”

“…Among all kinds of thin film HFSs, thermoelectric stack type thin film HFSs stand out due to their large output, high sensitivity, and fast response [19][20][21] . Researchers have carried out systematic and extensive research on thermoelectric stack type thin film HFSs, which are mainly composed of three parts, substrate, thermoelectric stack sensitive layer and thermal resistance layer [22][23][24][25][26][27][28][29] . The substrates are mainly made of two materials, ceramic or metal, with ceramic substrate Al2O3 2,17,22,25,28,29 predominating and to a lesser extent AlN ceramics 18, 27. The sensitive layer is mainly made of metals, metal oxides, most of which are platinum rhodium precious metals Pt-Pt/Rh 17,19,22,23,29 and ITO-In2O3 2,21,24,28 ，and some are other precious metals, such as constantan 25 and tungsten rhenium thermocouples 18 .…”

“…Researchers have carried out systematic and extensive research on thermoelectric stack type thin film HFSs, which are mainly composed of three parts, substrate, thermoelectric stack sensitive layer and thermal resistance layer [22][23][24][25][26][27][28][29] . The substrates are mainly made of two materials, ceramic or metal, with ceramic substrate Al2O3 2,17,22,25,28,29 predominating and to a lesser extent AlN ceramics 18, 27. The sensitive layer is mainly made of metals, metal oxides, most of which are platinum rhodium precious metals Pt-Pt/Rh 17,19,22,23,29 and ITO-In2O3 2,21,24,28 ，and some are other precious metals, such as constantan 25 and tungsten rhenium thermocouples 18 . Among them, ITO-In2O3, as a transparent conductive oxide, has the advantages of high-temperature resistance, high output, and strong oxidation resistance in hightemperature environments, which can be used as a substitute for precious metal thermopiles 28 .…”

Highly sensitive flexible heat flux sensor based on a microhole array for ultralow to high temperatures

“…The Schmidt-Boelter heat flux meter uses a thermocouple wire around a thermal resistance layer to form a thermopile, and the time lag of the sensor is large 18 . Thin-film heat flux sensors have thermopiles in thin film form, which are currently popular for heat flux measurement due to their small size, easy installation, and large measurement range 19 , 20 . However, existing studies focus more on HFSs used at high temperatures 21 and less on devices that are flexible, bendable, and easy to attach and install.…”