A Simple Quasi-2D Numerical Model of a Thermogage Furnace |
| |
Authors: | Khaled Chahine Mark Ballico John Reizes Jafar Madadnia |
| |
Affiliation: | (1) National Measurement Institute, NMIA, Bradfield Road, West Lindfield, NSW, 2070, Australia;(2) Faculty of Engineering, University of Technology, Sydney, PO Box 123, Broadway, NSW, 2007, Australia |
| |
Abstract: | A simple quasi-2D model for the temperature distribution in a graphite tube furnace is presented. The model is used to estimate
the temperature gradients in the furnace at temperatures above which contact sensors can be used, and to assist in the redesign
of the furnace heater element to improve the temperature gradients. The Thermogage graphite tube furnace is commonly used
in many NMIs as a blackbody source for radiation thermometer calibration and as a spectral irradiance standard. Although the
design is robust, easy to operate and can change temperature rapidly, it is limited by its effective emissivity of typically
99.5–99.8%. At NMIA, the temperature gradient along the tube is assessed using thermocouples up to about 1,500°C, and the
blackbody emissivity is calculated from this. However, at higher operating temperatures (up to 2,900°C), it is impractical
to measure the gradient, and we propose to numerically model the temperature distributions used to calculate emissivity. In
another paper at this conference, the model is used to design an optimized heater tube with improved temperature gradients.
In the model presented here, the 2-D temperature distribution is simplified to separate the axial and radial temperature distributions
within the heater tube and the surrounding insulation. Literature data for the temperature dependence of the electrical and
thermal conductivities of the graphite tube were coupled to models for the thermal conductivity of the felt insulation, particularly
including the effects of allowing for a gas mixture in the insulation. Experimental measurements of the temperature profile
up to 1,500°C and radial heat fluxes up to 2,200°C were compared to the theoretical predictions of the model and good agreement
was obtained. |
| |
Keywords: | ATJ graphite Blackbody Graphite felt Numerical model Thermogage |
本文献已被 SpringerLink 等数据库收录! |
|