Thermal ratcheting is required to be checked by most of the piping design codes, specifically the ASME B&PV Code. For cases where the variation of temperature distribution is not uniform, the existing ratchet check methodology for piping is inadequate and therefore the finite element analysis (FEA) is often used to perform ratchet checks. Thermal stratification, in which cold and hot fluid flows are layered in a relatively steady state condition, is a good example of non-linear/non-uniform temperature distribution across the pipe.
This paper develops straightforward equations to address thermal stratification in piping. Finite element analysis is used to benchmark the results.