Numerical analysis of low‐frequency properties in single‐junction thermal converters

Amagai, Yasutaka; Nakamura, Yasuhiro

doi:10.1002/tee.21739

Cited by 8 publications

(2 citation statements)

References 10 publications

(10 reference statements)

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“…At a 5% significance level, the error is 0.46 °C. [9] used a thermal model to compute the exponentially decreasing thermal drift of a single junction thermal converter based on a thermocouple's cold side temperature. [10] proved that the reported thermal voltage is governed by the temperature of the thermocouple along its whole length.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Temperature Drift with Thermocyclic Oxidation on K-Type Bare Thermocouples

2024

Teh. vjesn.

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The irrevocable variations in the thermoelectric properties arise in normally used bare type-K thermocouples that are subjected to high temperatures. Over an extended period of time, these long-term modifications may manifest themselves as a systematic shift in the thermocouple's characteristics. This paper investigates the temporal instability of thermocouple output at temperatures over 800 °C. This investigation focuses on the change in temperature output that occurs in thermocouples of varying diameters after they have been subjected to high temperatures for more than 365 hours. This data was used to assess the relationship between the amount of temperature drift with different lead diameters and the degradation of the material compositions of thermocouple thermoelements. It is critical to determine the pace at which the thermocouple material degrades over time. This paper concentrates in detail on the drift analysis of thermocouples of different diameters which were tested at high temperatures with their segmental material compositions. Within the scope of this investigation, the elemental analysis of the thermocouple could be carried out using scanning electron microscopy in conjunction with an energy dispersive X-ray (SEM-EDAX) both before and after the thermocouple had degraded. The results show that the thermoelectric response decreases dramatically and the highest drift reaches to about 196.4 µV for (Ø0.51 mm), about 118.6 µV for (Ø1.29 mm) and 79.2 µV for (Ø2.05 mm) thermocouples, respectively at 800 °C after prolonged usage of 365 hours. The highest thermal drift was achieved with [90-10] vol% Ni-Cr / [95-05] vol % Ni-Al, Mn, Si composite thermocouples, which related to the increased amount of the 2-3 oxide layers that were formed in the composite of bare thermoelements.

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Section: Introductionmentioning

confidence: 99%

Investigation of Temperature Drift with Thermocyclic Oxidation on K-Type Bare Thermocouples

2024

Teh. vjesn.

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“…To provide possible resolutions to the technical issues, a nonlinear electrothermal model of a TMJTC [14], [15] and an external circuit model [16], [17] that treated the thermal converter as a black box instead of solving the nonlinear parabolic heat conduction equation have been reported. Meanwhile, simplified electrothermal models of the SJTC at low frequencies [9], [13], [18], [19] have been developed to determine the ac-dc transfer differences. These models are based on the assumptions that the heat capacity of the thermocouple junction is ignored to simplify its geometries and the Seebeck coefficient of the thermocouple is treated as a constant value with respect to temperature when the output voltage is calculated.…”

Section: Introductionmentioning

confidence: 99%

Improved Electrothermal Simulation for Low-Frequency Characterization of a Single-Junction Thermal Converter

Amagai

Fujiki

2014

IEEE Trans. Instrum. Meas.

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We perform a numerical simulation for the lowfrequency characterization of a single-junction thermal converter down to 1 Hz using an improved electrothermal model. The lowfrequency characterization of a thermal converter below 10 Hz is of great importance for linking ac-dc transfer standards and lowfrequency ac voltage standards based on sampling methods. One feature of our model is the incorporation of the heat capacity for the thermocouple, which has previously been neglected to reproduce an accurate thermal time constant. Our model also includes the temperature dependence of the Seebeck coefficient in the thermocouple in addition to the temperature-dependent material parameters of the heater. To verify the simulation results, the calculated results are compared with the experimental results, which shows that our improved model well reproduces the measured data below 1 Hz. The estimated uncertainty of the simulated ac-dc transfer differences is 49 µV/V at 4 Hz. These results suggest that our model is a useful predictive tool at low frequencies.Index Terms-AC-DC difference, electrical variable measurement, numerical analysis, thermal converter, thermal voltage converter.

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Estimation of Thermo Oxidation on Chromel–Alumel Thermocouple

Pallavan¹,

Srinivasan

Arumugam

2021

Springer Proceedings in Materials

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Numerical analysis of low‐frequency properties in single‐junction thermal converters

Cited by 8 publications

References 10 publications

Investigation of Temperature Drift with Thermocyclic Oxidation on K-Type Bare Thermocouples

Investigation of Temperature Drift with Thermocyclic Oxidation on K-Type Bare Thermocouples

Improved Electrothermal Simulation for Low-Frequency Characterization of a Single-Junction Thermal Converter

Estimation of Thermo Oxidation on Chromel–Alumel Thermocouple

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