A fast-response microthermocouple

Abstract

A fast-response chromel-alumel (and chromel-constantan) microthermocouple is described and its dynamic characteristics are measured. The microthermocouple features a microdisk junction 0.08 mm in diameter and 2.5 μm thick. Its time constant in turbulent flow of liquid Refrigerant-113 (a poor heat conductor) is measured to be ∼4.6 ms. This time constant was reduced to ∼3.4 ms with a phase-lead compensation circuit. It was possible to distinguish between vapor and liquid phase temperatures in turbulent subcooled boiling flow of Refrigerant-113 with the compensated microthermocouple.

A study of local heat transfer mechanisms along the entire boiling curve by means of microsensors

“…They used a type E TC with a wire diameter of 20 µm and a bead diameter of about 60 µm with a junction shaped as a disk with a diameter of 80 µm and a thickness of 2.5 µm. They reported also on a new version of the TC, see [18] with an increased disk diameter of 100 µm and also an increased thickness of 4 µm.…”

“…For a fast response time of the TC, a thin wire is desirable. Flattening of the junction by any means [17,18] is not considered to be useful as the size of the junction is greatly increased. Consequently local measurementsespecially very close to the wall-are no longer possible.…”

“…They used a bare wire TC with 12 µm wire diameter but did not report the bead size which determines the thermal behavior. More recently, Beckman et al [17] developed a fast response TC and reported measurements in flow boiling of R 113. They used a type E TC with a wire diameter of 20 µm and a bead diameter of about 60 µm with a junction shaped as a disk with a diameter of 80 µm and a thickness of 2.5 µm.…”

Measurement of local liquid temperature using micro-thermocouple in subcooled flow boiling

“…STD(T (t)) < 0.1 ( 5 ) where STD is the standard deviation and L plays the role of to reducing the standard deviation to 10% of the original raw data. S is used to take into consideration the time constant of the micro-thermocouple, noisy and fluctuating temperature signal when the ATD is calculated.…”

“…Delhaye et al [3] used the statistical information provided by the Probability Density Function (PDF) of temperatures to determine the void fraction and temperatures in the case of subcooled boiling using 25 and 20 µm micro-thermocouples. Also, Roy et al [4][5][6][7] measured the temperatures of the liquid and vapor phases with the PDF method using R-113 as the working fluid. The micro-thermocouples used in these studies were of the complex type, with a diskshaped junction being used to fabricate them.…”