• Title, Summary, Keyword: Thermocouple

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A Review of Temperature Measurement of Fire Driven Flow Using Thermocouple - Measurement Bias (열전대에 의한 화재유동의 온도측정에 관한 검토 - 측정오차)

  • Kim, Sung-Chan
    • Fire Science and Engineering
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    • v.24 no.6
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    • pp.98-103
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    • 2010
  • A series of fire experiments have been performed to examine the measurement bias of the bare bead thermocouple widely used in fire testing and analyze the measurement bias of bare bead thermocouple comparing with the measured temperature using the aspirated thermocouple. The measured temperature of the bare bead thermocouple was lower than that of the aspirated thermocouple in the hot upper layer while it showed opposite trends in the upper layer. Also, the bare bead thermocouple showed higher measurement bias in the lower layer rather than upper layer in the compartment fire. The maximum relative percentage error of the bare bead thermocouple against the aspirated thermocouple reached 250% in the present study. The present study points out the need of correction process of the measured temperature by bare bead thermocouple for improving the reliability of the fire tests.

NUMERICAL ANALYSIS OF CONJUGATE HEAT TRANSFER INSIDE A THERMAL BOUNDARY LAYER CONSIDERING THE EFFECTS OF A FREE STREAM VELOCITY AND A THERMOCOUPLE POSITION (유속 및 열전대 위치의 영향을 고려한 열경계층 내부의 복합열전달 해석)

  • Jeon, B.J.;Lee, J.A.;Choi, H.G.
    • Journal of computational fluids engineering
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    • v.18 no.1
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    • pp.77-82
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    • 2013
  • The error in measuring temperature profiles by thermocouple inside boundary layer mostly comes from the conduction heat transfer of the thermocouple. The error is not negligible when the conductivity of the thermocouple is very high. In this study, the effect of conduction heat transfer of the thermocouple on the temperature profile inside boundary layer was examined by considering both free-stream velocity and a thermocouple position. The conduction error of an E-type thermocouple was investigated by numerical analysis of three-dimensional conjugate heat transfer for various velocity profiles of boundary layer and thermocouple positions.

Measurement of Compression Temperature in Cylinder by using the Compensation Circuit of Thermocouple (열전대 보상회로에 의한 실린더 내에서의 압축온도 측정)

  • Kwon, Soon-Ik
    • Journal of the Korean Society of Industry Convergence
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    • v.3 no.2
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    • pp.149-154
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    • 2000
  • The purpose of this study is to measure the compression temperature in cylinder by using the fine thermocouple. As for using the thermocouple, it's response time delay should be regarded, even if it is a fine one. So, the output of thermocouple needs some compensation. The compensation circuit, which consists of a differential and an adding circuit is used for the compensate the time lag. And the time constant of the compensation circuit is determined the time between the TDC and the maximum point of the thermocouple output. Using this compensation circuit, the compression temperature is investigated of the cylinder in the diesel engine.

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Characteristics variation of thermal time constant of thermocouples by the structure changes (열전대 구조변화에 의한 열시정수 특성 변화)

  • Gam, Kee-Sool
    • Journal of Sensor Science and Technology
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    • v.18 no.2
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    • pp.103-109
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    • 2009
  • Thermal time constant measurement system was designed and fabricated to measure the thermal time constant, which shows a dynamic property of the thermocouple. Type K thermocouple samples were fabricated with variable shape each other and the thermal time constants of thermocouples were measured using the home-made thermal time constant measurement system. Thermal time constants of 12 type K thermocouple samples were distributed from 0.03 s to 8.2 s. It showed experimentally that the thermal time constant of thermocouple was increased linearly for the increase of the sheath diameter of thermocouple.

Fabrication of Embedded Thermocouple Sensor and Experimental Study on Measurement of Interface Temperature for Dry Friction (임베디드 서모커플 센서 제조 및 미끄럼 마찰 계면온도 측정에 관한 실험적 연구)

  • Jang, Beomtaek;Lim, Youngheon;Kim, Seocksam
    • Tribology and Lubricants
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    • v.29 no.6
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    • pp.372-377
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    • 2013
  • This study investigated the interface temperatures for the sliding friction of three types of pins fabricated with thermocouple wires by the suction casting method. Optical microscopy was used to examine the surrounding material state at the bonding interface with the thermocouple wires. Friction tests were performed under dry sliding conditions against stainless steel 304 at nominal stresses of 1.42-4.25 MPa and sliding speeds of 0.5-1.25 m/s. Tribological data were collected using a custom-made pin-on-disk apparatus that measured the interface temperature and corresponding friction coefficient. Static tests were performed to demonstrate the functionality and reliability of the thermocouple wires-combined temperature sensor (TCTS). Each TCTS showed good linearity and sensitivity and very similar response times for the thermocouple and critical temperature during sliding friction.

Development of Thermocouple Sensor for Thermal Boundary Layer Measurement (온도 경계층 측정용 열전대 센서 개발)

  • Seo, Jongbeom;Han, S.
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.12
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    • pp.983-990
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    • 2014
  • This research focused on designing an appropriate thermocouple sensor for a thermal boundary layer with a large temperature gradient. It was designed to minimize the conduction error from a constant temperature wall in a boundary layer. A $79.9-{\mu}m$ thermocouple was chosen, and a five-axis device jig was developed to fabricate a butt-welded thermocouple, which is different from arc-welded junction thermocouples. This was used to minimize the size of the thermocouple junction. In addition to fabricating butt-welded thermocouples, a thorough calibration was conducted to decrease the internal error of a multimeter to ensure that the data from the butt-welded and regular thermocouples were almost the same. Based on this method, a butt-welded thermocouple with a small junction was found to be suitable for measuring the temperature in a thermal boundary layer with very large thermal gradients. Using this thermal boundary layer probe, the thermal boundary layers in a turbine cascade were measured, and the Nusselt numbers were obtained for the turbine endwall.

Measurement of local wall temperature and heat flux using the two-thermocouple method for a heat transfer tube

  • Ahn, Taehwan;Kang, Jinhoon;Jeong, Jae Jun;Yun, Byongjo
    • Nuclear Engineering and Technology
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    • v.51 no.7
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    • pp.1853-1859
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    • 2019
  • The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method.

Time Constant of a Fine-Wire Thermocouple Immersed to Fluids (유체에 잠겨있는 가는 열전대의 시간상수 측정)

  • 송치성
    • Journal of the Korean Society of Marine Engineering
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    • v.22 no.2
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    • pp.190-199
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    • 1998
  • a new measuring method is suggested to determine the time constant of a thermocouple wire to be applied for the measurement of the true fluid temperatures in varying flow states. Based on the techniques of internal heating which are commonly used to measure mean time constants we extend the existing method to measure instantaneous time constants continuously. A method of measurement and analysis is presented and verified experimentally.

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Design of Respiratory Sensor System for polysomnography using Thermocouple (Polysomnography를 위한 열전대 호흡센서 시스템의 설계)

  • 우용규;정도언;박광석
    • Proceedings of the IEEK Conference
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    • pp.121-123
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    • 2000
  • Changes in breathing pattern and apnea both can be !he result of sleep disorders. The focus of this paper is to develop methodologies to monitor the breathing pattern and to detect apnea. An accurate recording of the respiratory phase can be carried out with different methods. One of these methods is the use of a thermocouple, which reacts to the variation in air temperature, placed in the nose and mouth of the patient. The K-type thermocouple was used because it has high reliability, thermo-stability, and good corrosion resistance. And also, it has a considerable long time constant that gives a low cut-off frequency, well below the respiratory frequency and thereby causing a large phase difference. The result showed that timing of respiration was accurately obtained with the AD595, amplifier for K-type thermocouple.

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Temperature Measurement Method with Radiation Correction for Very High Temperature Gas (복사 간섭 보정을 통한 초고온 가스 온도 측정 방법)

  • Kim, Chan-Soo;Hong, Sung-Deok;Seo, Dong-Un;Kim, Yong-Wan;Lee, Won-Jae
    • Proceedings of the KSME Conference
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    • pp.2059-2063
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    • 2008
  • When a thermocouple is placed in a high temperature gas-flow stream, the measured temperature could be biased from the true gas temperature due to a large radiation heat loss from a thermocouple surface to its surroundings. In this study, two thermocouples of unequal diameters with 1/8 inch and 1/16 inch are used to correct the radiation effect. The method is called the reduced radiation error (RRE). The preliminary test results show that the radiation and the sheath conduction cannot be negligible for the gas temperature measurement. To minimize the sheath conduction effect, all the thermocouples will have a grounded junction and 1/8 inch thermocouple will be replaced with 1 mm thermocouples. In addition, the computational fluid dynamics code analysis shows that there is a negligible temperature difference between the positions where the thermocouples were installed.

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