Prediction of Fluid Temperatures From Measurements of Outside Wall Temperatures in Pipes

The monitoring of the fatigue induced by thermal transients in thick-walled structures becomes more and more currently performed, mainly on equipment the failure of which could present severe implications on the environment. The easiest way of performing this monitoring is by use of Green’s functions in a convolution integral of the measured fluid temperatures to assess the stresses at the points of interest. Numerous cases, however, exist where the fluid temperatures are not available and only an outside wall temperature measurement is feasible. This paper describes the development and the industrial application of the so-called “inverse” transfer functions to predict the evolution of the fluid temperature from measurements of the metal temperature either at the outside or in the wall of the considered equipment. Some applications are shown for the particular case of the thermal stratification in piping systems.