MTDATA – Phase Diagram Software from the National Physical Laboratory









Modelling the thermal conductivity of oxide scales


A significant number of high temperature components that are exposed to steam environments are heat exchangers, where the steam is heated to a given temperature. Any reduction in the thermal conductivity of the heat exchanger will result in a loss of efficiency and possibly overheating of the component leading to a potential failure through creep mechanisms. Therefore knowledge of the thermal conductivity of the scale and characterisation of the evolution of this property with scale thickness and oxidation conditions will allow for a more precise component lifetime prediction.

The aim of this task was to develop a procedure for the measurement of thermal conductivity using the laser flash method. This was achieved by using the laser flash equipment to measure the thermal diffusivity of the composite scale and the metal substrate. A model was then developed to take the composite data obtained from the laser flash and separate the contributions of the different layers, such that the thermal conductivity of the scale could be evaluated as opposed to being associated with the metal substrate. Measurements were performed on a copper/braze sample and on steam oxidised P92 samples.

TherMOL fitted curve and experimental data obtained using the laser flash technique


Examples of the model can be viewed using the following links, the first for a simple one material test using Copper, the second showing the results of the heat transfer for the composite Copper/Braze sample. Further information on TherMOL is available here.


Copper TherMOL simulation (size 1,020 kb)

Copper/Braze TherMOL simulation(1,030 kb)

If you have problems running these animations please use the following links: Copper (size 7,243 kb) and Copper/Braze (size 6,153 kb)