Off-center hot spots: Double thermocouple determination of the thermal gradient in a 1.27 cm (1/2 in.) CaF2 piston-cylinder furnace assembly
Off-center hot spots: Double thermocouple determination of the thermal gradient in a 1.27 cm (1/2 in.) CaF2 piston-cylinder furnace assembly
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偏心热点：双热电偶测定 1.27 厘米（1/2 英寸）CaF2 活塞缸炉组件中的热梯度
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
A. Dana Johnston
中科院分区：
文献类型：
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作者：
Jennifer M. Pickering;Brandon E. Schwab;A. Dana Johnston
在1.27 cm（1/2 in.）活塞-气缸装置，以绘制热梯度图，并在900-1500 °C的温度区间内定位CaF 2-石墨炉组件的峰值温度。一个意想不到但可重复的结果是，热峰从石墨加热器管的垂直中心显著向上移位（朝向钢基座塞）。我们的组件的热点被定义为比峰值温度低不超过10 °C的区域，它从炉子的中心向上移动，并随着温度的升高稍微向中心移动。在914 °C的最高温度下，热点的中心在炉的中点上方2.6mm，而在1510 °C（所研究的最高温度）下，热点的中心在炉的中心上方2.2mm。热点的宽度从较低温度下的3.2 mm变化到1510 °C下的2.2 mm。我们将热点的向上位移归因于下部碳化钨活塞（在200 °C时k = 100 W/mK）相对于上部不锈钢基座塞（在600 °C时k = 25 W/mK）的更大热导率。活塞向下导热的效率显然比钢塞向上导热的效率高，因此使热点从炉子中心向上移动。
Abstract Double-thermocouple experiments were carried out at 10 kbar in a 1.27 cm (1/2 in.) piston-cylinder apparatus to map the thermal gradient and locate the peak temperature of a CaF2-graphite furnace assembly over the temperature interval 900-1500 °C. An unexpected but reproducible result was that the thermal peak is displaced upward significantly (toward the steel base plug) from the vertical center of the graphite heater tubes. The hot spot of our assembly, defined as the region no more than 10 °C cooler than the peak temperature, is displaced upward from the center of the furnace and moves slightly toward the center with increasing temperature. At a maximum temperature of 914 °C, the center of the hot spot was 2.6 mm above the mid-point of the furnace, while at 1510 °C, the highest temperature investigated, the center of the hot spot was 2.2 mm above the center of the furnace. The hot spot varies in width from 3.2 mm at lower temperatures to 2.2 mm at 1510 °C. We attribute the upward displacement of the hot spot to the greater thermal conductivity of the lower tungsten-carbide piston (k = 100W/mK at 200 °C) relative to the upper stainless steel base plug (k = 25 W/mK at 600 °C). The piston apparently conducts heat more efficiently downward than the steel plug does upward, thus displacing the hot spot upward from the furnace center.