Transient Response of an Intrinsic Thermocouple

Abstract

Where rapid heating is encountered, as in a prompt-burst nuclear reactor, a thermocouple with a rapid time-response is necessary to monitor the temperature of the specimen in question. Because all thermocouples have some mass, they cannot have an infinitely fast response. However, an intrinsic-type thermocouple has less thermal inertia than the usual welded-bead type. Thus it is a natural choice for the measurement of transient surface temperatures of conducting solids. In this report an analytical expression is obtained for the transient response of an intrinsic thermocouple. In support of the analysis, experimental data are presented which were obtained by means of a capacitor bank pulse-heating technique. It is concluded that thermocouple wires of small diameter and low thermal conductivity respond the fastest. As an example, a 1-mil constantan wire on a copper substrate produces 95 percent of the steady-state emf in 3 μsec.

Measurement and estimation of thermophysical properties of nickel based superalloys

“…Since Ni 3 Al is the principal constituent of the c9 phase the amount of c9 phase was expressed as a function of the Al content of the alloy. The following relation was found 13,18 c 0 (at: À %)~16 : 1z10 : 6(wt À %Al)…”

Spatial power profiling method using visual information in reactors with optically transparent coolants

“…Temperature sensors can be placed within fuel elements to give a much faster response time, but this requires the presence of instrumentation within the actual fuel element, and is therefore usually only done in some research reactors [7] [8] [9]. More recently, some work has been done investigating the use of thermoacoustic sensors as a temperature sensing method that does not require external power [10] [11].…”

Low-noise audio amplifiers and preamplifier for use with intrinsic thermocouples

“…Thermocouple response times, which depend upon the sample and thermocouple materials being used, can be calculated to the 95% level of maximum temperature rise. 1 Response times for a 10-mil-diam chromel-alumel thermocouple wire range from ~2 to 10 ms, as compared with ~500 ji9 to ~1 ms for a 5-mil-diam wire. Figure 2 shows the cross section of an intrinsic thermocouple used at LASL for determining thermal properties of fuel elements that have a central bore.…”