Mattia Bergagio
About me
Experimental analysis of thermal fatigue
Thermal fatigue ageing accelerated by temperature cycling between low and high temperatures affects nuclear power plants, refineries, and petrochemical and liquefied natural gas plants. This temperature cycling is often triggered by turbulent mixing of non-isothermal flows. Despite its relevance, the whole phenomenon is not fully grasped yet.
In our HWAT loop, we have performed experiments to measure temperature fluctuations on the walls of the mixing region. Amplitudes and frequencies of these fluctuations have been derived using Hilbert-Huang transforms.
Large eddy simulations of thermal mixing
Large eddy simulations of mixing of non-isothermal flows are validated against the above experimental data. Then, thermal stresses in the walls of the mixing region are computed. Once stresses are known, fatigue crack initiation and growth are estimated.
Our method can be used to determine fatigue risk at mixing points and to establish inspection intervals and service programs. Furthermore, it can supply data for decision on repair or replenishment of pipe joints.
Heat flux assessment from thermocouple measurements
Heat flux on inaccessible boundaries has been estimated by solving a transient inverse heat conduction problem with redundant data on accessible boundaries. Our method has been verified in representative cases.