New non-invasive thermal sensor design for a pipe flow

Abstract

A new non-invasive thermal sensor based on transient heat flux and temperature measurements has been developed for accurate and reliable thermal measurement in piping systems. The sensor is clamped onto the outer surface of the pipe and covered by a thin-film heater and heat flux sensor mounted over a thin-film thermocouple. Previously, when the thin-film thermocouple was mounted directly on the copper pipe surface, there was a small temperature shift that affected the accuracy and reliability of the measurements. To eliminate this temperature shift, a new design was developed using a single layer of Kapton tape with an adhesive (dielectric material) between the butt-welded thermocouple foils and the pipe wall. This design gives more accurate, reliable, and practical temperature measurements over a range of fluid flow rates and bulk fluid temperatures. Encouraging temperature measurement results in 150 tests of this new design gave accurate estimates of the internal mean fluid temperature without environmental interference. A new parameter estimation code was developed to estimate the optimal system parameters by using the minimum root mean square error between the calculated and experimental sensor temperature values. The resulting new non-invasive thermal sensor can be used to estimate mean fluid temperature in a variety of applications.