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| Furnaces for the Primary Laboratory | |
| Heat Pipe Furnaces | |
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Essentially Gradient Free - From Indium to Copper Points |
 From Databook 1 |
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 Data Sheet |
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| Heatpipes provide the ideal conditions for the creation and maintenance of freeze points from ITS-90. 1. The furnace core is an especially-designed stress-free isothermal heat pipe, which provides a very low thermal gradient along the core working length. The furnace heater is of the parallel-tube design used at NIST. 2. The heat pipe is designed so that the inner wall is not subject to thermal expansion stresses from the outer wall before the heat pipe reaches conduction temperature. The working fluid is permanently and safely sealed within the plasma-arc-welded enclosure. 3. Three temperature ranges are available: Low Temperature: 125ºC to 250ºC, 17702W, Water High Temperature: 400ºC to 1000ºC, 17702P, Potassium Very High Temperature: 500ºC to 1090ºC, 17702S, Sodium Connections are provided for a water supply of 0.5 to 1 litre per minute to cool the top of the apparatus (not on 17702W). Water supply and waste connections may be ordinary garden hose. Use without cooling is not recommended above 700ºC. 4. An advanced proportional electronic control system controls the furnace temperature. The control may be self-calibrated using Freeze Point Cells as references. Two entirely independent over-temperature safety circuits are provided. The active safety is a second (off-on) control circuit driven by a second thermocouple. The passive safety is a fusible link in the main power supply. |
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