Temperature Calibration in Cold-Seal Pressure Vessels

Abstract

Experiments at \({{P}_{{{H}_{2}}O}}=1Kb\) with a 1 inch o.d. hydrothermal vessel showed that a filler rod is an important factor in measurement of internal temperatures with an external thermocouple. Without a filler rod, significant temperature differences exist between the external and internal thermocouple readings with the long axis of the vessel positioned horizontally, and in the vertical position with the end of the vessel containing the closure nut oriented up. Steady-state convection of water within the vessel removes sufficient heat that the internal thermocouple is maintained at lower temperatures than the external thermocouple. The temperature difference is markedly reduced in runs in these orientations with a filler rod in the vessel. Furthermore, the presence of a filler rod reduces thermal gradients along the axis of the vessel. Little difference exists between the external and internal thermocouple readings with the axis of the vessel vertical and with the closure nut down. Similar results were obtained with a 1 1/4 inch o.d. vessel.