The use of a mass transfer technique to infer heat transfer coefficients on film cooled turbine components

摘要

The swollen polymer technique is a method for measuring mass transfer coefficients under steady-state conditions. Heat transfer data can then be inferred by analogy, as with the more familiar naphthalene sublimation technique. The swollen polymer technique has two significant advantages. Firstly, it can be used with interferometric measuring methods to give a panoramic view of the distribution of the transfer coefficient over the working surface. Secondly, the mass transfer process is reversible, allowing repeated use of the working surface. Changes in thickness of a polymer coating on the working surface, initially swollen with an ester, are measured, using holographic interferometry to yield a fringe pattern depicting loci of equal transfer coefficient over the surface. The paper describes the basis of the method, its advantages, limitations and future potential. Extension of the technique for the simultaneous measurement of effectiveness and heat transfer coefficient is described and its further extension for use with curved surfaces is outlined.