A model for the time response of solid-embedded thermocouples
- 238 Downloads
Unlike the transient response of a fluidimmersed thermocouple, and in contrast to common belief, the time response of a solid-embedded thermocouple is far from being similar to that of a first-order process. The current study arises from efforts to characterize the transient response of a solid-embedded thermocouple as a result of a step-like temperature change of the measured domain. Results of this study suggest that the response function of the thermocouple is nearly exponentially dependent on the square root of Fourier number (dimensionless time). It follows that, with respect to fluid temperature measurements, significantly faster time response is expected at the initiation of the process on one hand, and much longer time is required for reaching a steady-state temperature on the other hand. It is shown that the thermal diffusivity of the thermocouple is required to be at least one order of magnitude higher than that of the measured domain in order to obtain meaningful results in transient measurements.
KeywordsThermocouple time response mathematical analysis solid domain temperature measurements
Unable to display preview. Download preview PDF.
- 2.Benedict, R.P., Fundamentals of Temperature, Pressure, and Flow Measurements, Wiley-Interscience, New York (1984).Google Scholar
- 3.Holman, J.P., Experimental Methods for Engineers, 6th ed., McGraw-Hill, New York, (1994).Google Scholar
- 4.Omega Inc., The Temperature Handbook, Catalog Series,29,Stamford, CT (1996).Google Scholar
- 5.Miller, R.W., Flow Measurements Engineering Handbook, 3rd ed., McGraw-Hill, New York (1996).Google Scholar
- 6.Rabin, Y., “Uncertainty in Temperature Measurements During Cryosurgery,”Cryo-Lett,19 (4),213–224 (1998).Google Scholar
- 7.Rabin, Y., “Uncertainty in Measurements of Fluid Temperature in Tubes,”Cryo-Lett.,19, (5),319–326 (1998).Google Scholar
- 8.Holman, J.P., Heat Transfer, 6th ed., McGraw-Hill, New York (1986).Google Scholar
- 9.Zehnder, A.T. andRosakis, A.J., “On the Temperature Distribution at the Vicinity of Dynamically Propagating Cracks in 4340 Steel,”J. Mech. Phys. Solids,39,385–415 (1991).Google Scholar
- 10.Rabin, Y., Julian, T.B., andWolmark, N., “A Compact Cryosurgical Apparatus for Minimal-invasive Cryosurgery,”Biomed. Instr. Tech.,31,251–258 (1997).Google Scholar
- 12.Wally, K., “The Transient Response of Beaded Thermocouples Mounted on the Surface of a Solid,”ISA Trans.,17 (1),65–70 (1978).Google Scholar