NIM gas controlled sodium heat pipe

Abstract

Gas controlled heat pipes (GCHPs) provide a uniform, stable and reproducible temperature zone to calibrate thermometers and thermocouples, and to realize defining fixed points using a calorimetric method. Therefore, to perform such investigations, a GCHP furnace using sodium as its working fluid was constructed at the National Institute of Metrology (NIM), China. Also, investigations into the thermal characteristics of the NIM gas controlled sodium heat pipe were carried out. The temperature stability over 5 hours was better than ±0.25 mK while controlling the pressure at 111250 Pa. The temperature uniformity within 14 cm from the bottom of the thermometer well was within 0.3 mK. While keeping the pressure stable at the same value, 17 temperature determinations were performed over 14 days, obtaining a temperature reproducibility of 1.27 mK. Additionally, the NIM gas controlled sodium heat pipe was compared with the sodium heat pipe produced by INRiM. The temperature in the INRiM sodium heat pipe operating at 111250 Pa was determined, obtaining a difference of 21 mK with respect to the NIM GCHP. This difference was attributed to sodium impurities, pressure controller capabilities and reproducibility, and instabilities of high temperature standard platinum resistance thermometers (HTSPRTs). Further investigations will be carried out on extending the pressure/temperature range and connecting both GCHPs to the same pressure line.

Gas-controlled heat pipes in metrology: More than 30 years of technical and scientific progresses

“…Under this cooperation, INRiM manufactured, filled, characterized and delivered to NIM two gas-controlled HPs, one filled with mercury and one with sodium to be connected together in the Temperature Amplifier configuration (Figure 15). During the period from 2009 to 2011, a further gas-controlled sodium HP system was successfully developed at NIM [39]. Also, investigations into the thermal characteristics of the NIM gas controlled sodium HP were carried out.…”

Numerical Study on the Effects of the Wick Structure of an Annular Heat Pipe on the Isothermal Performance

“…Compare with heat pipes for heat transfer, the length diameter ratio of gas-controlled heat pipe or other heat pipe for metering is small, and there is a pressure control system in particular. The isothermal performance and temperature stability of gas-controlled heat pipes are much better than other heat pipes due to the pressure control system [9]. The inert gas of the pressure control system is directly connected with the inner part of the heat pipe, and the pressure of the working fluid of the heat pipe is adjusted by controlling the pressure of the inert gas.…”