Thermal Characteristics of a Dodecane Heat‐pipe over the Range from 190 to 260 °C and Related Impurity Effects

To improve the calibration‐comparison capability in the range 600 to 962 °C, the BNM‐INM is studying the possibility of connecting to the same pressure control system several heat‐pipes filled with different working fluids, in order to set‐up a “temperature amplifier.” One of these heat‐pipes is intended to receive the standard platinum resistance thermometer (SPRT), and so must have an operating temperature range which can ensure stability of the SPRT. The BNM‐INM decided to test a heat‐pipe filled with dodecane. The effect of impurities on the thermal characteristics of a dodecane heat‐pipe has been studied using two samples (99 % and 99.8 % purity). A significant improvement has been observed using the purest dodecane. The dodecane vapour pressure curve has been determined between 190 °C and 260 °C with an expanded uncertainty of about 16 mK.