Flow Viz
Heat/Mass Transfer

In these investigations, we measure the local mass sublimation from the turbine blade surfaces. With this information we can determine the mass transfer coefficient, and using the analogy between heat and mass transfer we can determine the analogous heat transfer coefficients on the blade surfaces.

The mass transfer coefficient can be found by measuring the local depth change on the naphthalene surface, the wind tunnel exposure time and by using a few physical properties of naphthalene, as shown below...

The mass transfer coefficent data is made dimensionless, the Sherwood number, using a length scale (the blade chord length) and the Diffusion coefficient of naphthalene vapor into air.

Finally, since the equations governing mass diffusion and heat conduction are similar, we can convert the mass transfer results into equivalent heat transfer results via the heat/mass transfer analogy. The dimensionless heat transfer coefficient, Nusselt number, can be found using the equation below using the Prandtl and Schmidt numbers of air and naphthalene respectively. The exponent in the equation depends on the flow situation and the boundary layer state.

The data we acquire on the suction side and pressure side of the blade is very detailed. This is one of the advantages of using the mass transfer technique.