A Thermocouple Homogeneity Scanner Based on an Open Pressure-Controlled Water Heatpipe

Abstract

This paper demonstrates a low-cost, high-performance thermocouple homogeneity scanner based on a pressure-controlled water heatpipe that is open to the atmosphere. With this arrangement, very much like a steam-point apparatus, the atmosphere provides the controlled pressure and the buffer gas for the heatpipe, and the isothermal zone is close to 100 • C. The thermocouple is inserted into the steam within the heatpipe through a plastic membrane so that the gradient is imposed over a spatial region determined primarily by heat flow within the thermocouple body, and can be as small as a few millimeters. The paper explains the construction of the scanner, and presents results of example scans demonstrating the uniformity and resolution of the scanner.

Thermocouple homogeneity scanning

“…Abdelaziz [19] (227 °C) Tamba [18] (Zn, Al, Ag, Cu and Pd) Kim [16] (550 °C, 750 °C and 950 °C) Fenton [11] (70 °C) Hill [15] (250 °C) White d [20] (100 °C) Holmsten [21] (300 °C) Ogura [22] (Cu)…”

“…Media with a high heat capacity and a high thermal conductivity are best. The dual heat-pipe scanner at MSL, which exploits a change of state by using direct immersion into the vapour space of a heat pipe [20,26], is superior to direct immersion in liquids such as water, oil or salt [11,15,25], which is, in turn, better than air-coupled scanning systems employing furnaces [45], fixed points [46], and thermowells [18,24]. Air coupling is usually required for the low-temperature zone, and made better with the use of forced air convection to improve the thermal contact with the air.…”