New portable instrument for the measurement of thermal conductivity in gas process conditions (original) (raw)
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The design of high-temperature thermal conductivity measurements apparatus for thin sample size
MATEC Web of Conferences, 2017
This study presents the designing, constructing and validating processes of thermal conductivity apparatus using steady-state heat-transfer techniques with the capability of testing a material at high temperatures. This design is an improvement from ASTM D5470 standard where meter-bars with the equal cross-sectional area were used to extrapolate surface temperature and measure heat transfer across a sample. There were two meter-bars in apparatus where each was placed three thermocouples. This Apparatus using a heater with a power of 1,000 watts, and cooling water to stable condition. The pressure applied was 3.4 MPa at the cross-sectional area of 113.09 mm2 meter-bar and thermal grease to minimized interfacial thermal contact resistance. To determine the performance, the validating process proceeded by comparing the results with thermal conductivity obtained by THB 500 made by LINSEIS. The tests showed the thermal conductivity of the stainless steel and bronze are 15.28 Wm-1K-1 and 38.01 Wm-1K-1 with a difference of test apparatus THB 500 are-2.55% and 2.49%. Furthermore, this apparatus has the capability to measure the thermal conductivity of the material to a temperature of 400 ° C where the results for the thermal conductivity of stainless steel is 19.21 Wm-1K-1 and the difference was 7.93%.
A New Instrument for the Measurement of the Thermal Conductivity of Fluids
International Journal of Thermophysics, 2006
The transient hot-wire technique is at present the best technique for obtaining standard reference data for the thermal conductivity of fluids. It is an absolute technique, with a working equation and a complete set of corrections reflecting departures from the ideal model, where the principal variables are measured with a high degree of accuracy. It is possible to evaluate the uncertainty of the experimental thermal conductivity data obtained using the best metrological recommendations. The liquids proposed by IUPAC (toluene, benzene, and water) as primary standards were measured with this technique with an uncertainty of 1% or better (95% confidence level). Pure gases and gaseous mixtures were also extensively studied. It is the purpose of this paper to report on a new instrument, developed in Lisbon, for the measurement of the thermal conductivity of gases and liquids, covering temperature and pressure ranges that contain the near-critical region. The performance of the instrument for pressures up to 15 MPa was tested with gaseous argon, and measurements on dry air (Synthetic gas mixture, with molar composition certified by Linde AG, Wiesbaden, Germany, Ar-0.00920; O 2-0.20966; N 2-0.78114), from room temperature to 473 K and pressures up to 10 MPa are also reported. The estimated uncertainty is 1%.
Dynamic thermal conductivity sensor for gas detection
Sensors and Actuators B: Chemical, 2004
A dynamic thermal conductivity sensor for gas detection based on the transient thermal response of a SiC microplate slightly heated by a screen-printed Pt resistance is described. This sensor is developed for specific applications such as the determination of carbon monoxide content in hydrogen for fuel cell, or that of methane in biogas applications. On the contrary of existing devices, the apparatus developed here does not need any reference cell, it operates in transient mode near room temperature ( T ≈ 5 K in air), so has a very low power requirements (≈5 mW) and keeps the gas near thermal equilibrium which simplifies the mathematical model and eases data processing. In test gases mixtures (N 2 + He), absolute and precise measurement of the gas thermal conductivity have been achieved, leading to the exact molar fraction of the gas to detect with a good reproducibility. (P. Tardy).
Journal of the Brazilian Chemical Society, 2004
Este artigo apresenta um procedimento para determinar a condutividade térmica de gases através de injeção por pulso, utilizando um detector de condutividade térmica (TCD). As medidas foram efetuadas à 323K e pressão atmosférica, com um sensor de filamento de tungstênio de 160 Ω. Através de aproximações bem definidas, foi possível transformar uma equação de segunda ordem não-linear, que descreve a saída do sensor como uma função de condutividade térmica e calor específico a volume constante (Cv), em uma equação linear de primeira ordem. De acordo com esta equação, o sinal elétrico do sensor, elevado ao quadrado e integrado em função do tempo, multiplicado pelo Cv, é proporcional a razão do Cv pela condutividade térmica. Os resultados experimentais obtidos com os gases Ar, N 2 , O 2 , CH 4 , CO 2 , C 2 H 4 , C 3 H 6 e i-C 4 H 8 estão de acordo com o modelo teórico proposto e a correlação de linearidade confirma a validade do método proposto.
Measurement Techniques and Considerations for Determining Thermal Conductivity of Bulk Materials
Physics of Solids and Liquids, 2004
Described in this paper is an apparatus in which bulk samples can easily be mounted on a removable puck for thermal conductivity measurements and then placed in the described measurement system. This rapid mounting and measurement system uses a standard steady-state absolute thermal conductivity measurement but allows for rapid measurement and excellent thermal stability coupled with the use of a closed cycle refrigerator. The distinction of this system is rapid mounting and measurement of thermal conductivity over a broad temperature range without sacrificing accuracy and precision in data acquisition. In addition, this system allows for versatility in its use. The design of this apparatus, measurement specifications, and thermal conductivity data on several standard materials measured in this system are presented. Ó
International Journal of Thermophysics, 2008
This paper describes the final refinements of a novel application of the transient hot-wire technique developed for the absolute, accurate measurements of the thermal conductivity of solids. Although the technique was originally developed five years ago, these new refinements allow a full understanding of the method and hence the performance of measurements with an absolute uncertainty of less than 1%. New measurements of Pyroceram 9606 up to 420 K are reported. The maximum deviation of the present measurements is 0.54%, while their standard deviation at the 95% confidence level is 0.25%. Since May 2007, Pyroceram 9606 is a European Commission certified thermal conductivity reference material, designated as BCR-724, with an uncertainty of ±6.5% at the 95% confidence level.
A New Guarded Hot Plate Designed for Thermal-Conductivity Measurements at High Temperature
International Journal of Thermophysics, 2014
The Laboratoire National de Métrologie et d'Essais has developed a new guarded hot-plate apparatus operating from 23 • C to 800 • C in the thermalconductivity range from 0.2 W•m −1 •K −1 to 5 W•m −1 •K −1. This facility has been specifically designed for measuring medium thermal-conductivity materials at high temperature on square specimens (100 mm side), which are easier to machine than circular ones. The hot plate and cold plates are similar with a metering section independent from the guard ring. The specimens are laterally isolated by an air gap of 4 mm width and can be instrumented by temperature sensors in order to reduce effects of thermal contact resistances between the specimens and the heating plates. Measurements have been performed on certified reference materials and on "calibrated" materials. Relative deviations between thermal conductivities measured and reference values are less than 5 % in the operating range.
International Journal of Thermophysics, 2015
This paper presents a critical review of current industrial techniques and instruments to measure the thermal conductivity of thermal insulation materials, especially those insulations that can operate at temperatures above 250 • C and up to 800 • C. These materials generally are of a porous nature. The measuring instruments dealt with here are selected based on their maximum working temperature that should be higher than at least 250 • C. These instruments are special types of the guarded hot-plate apparatus, the guarded heat-flow meter, the transient hot-wire and hot-plane instruments as well as the laser/xenon flash devices. All technical characteristics listed are quoted from the generally accessible information of the relevant manufacturers. The paper includes rankings of the instruments according to their standard retail price, the maximum sample size, and maximum working temperature, as well as the minimum in their measurement range.
DESIGN, CONSTRUCTION AND EVALUATION OF A THERMAL CONDUCTIVITY METER BASED ON ASTM E1225 STANDARD
The focus of this work is the design, construction and evaluation of a thermal conductivity meter apparatus based on ASTM E-1225 standard. The thermal conductivity is a heat-transport propriety and with the development of new materials the determination of thermophysical properties for its correct use becomes necessary. The apparatus was projected in CAD software and the material selection was done following the standard recommendations. For the meter bars were used 304 stainless steel, since its thermal conductivity is known. The heater was made with an aluminum cylinder block and a cartridge electric resistance. The cooling system was assembled using a Peltier thermoelectric plate and a fin heat sink equipped with a fan. Lastly, a steel pipe was used for building the guard cylinder. In order to evaluate the apparatus, the first specimen tested was the 304 stainless steel, the same material as the meter bars. The result of thermal conductivity showed an error of 6% relative to the value found in literature. However, in this test the temperature of isothermal guard cylinder was lower than the temperature required by the standard. Thus, the future goals will be the development of a temperature control for the guard cylinder and realization of more tests with different materials. NOMENCLATURE k thermal conductivity, W/mK L distance between a temperature difference, m q c conduction heat flux, W/m 2 r A meter bars and specimen radius, m r B guard cylinder inner radius, m T temperature, K T i temperature at Z i , K T average temperature, K Z i position as measured from the right end of the column, m