A REVIEW OF MASS-TRANSFER MEASUREMENTS USING NAPHTHALENE SUBLIMATION

The naphthalene sublimation method can be used to study mass and heat transfer with confidence for a variety of applications, but with certa in restrictions. This method is particularly useful in complex flews a nd geometries and for flows with large gradients in wall transport rat e. Mass transfer boundary conditions analogous to isothermal and adiab atic walls in convective heat transfer can be easily imposed. Furtherm ore, the nature of mass transfer allows one to impose these boundary c onditions such that errors analogous to conductive losses in a wall ar e not present. The test specimen can be easily prepared by several met hods, including dipping, machining, spraying, and casting. The local t ransfer coefficients can be determined with high accuracy and in detai l by automated measurement systems that eliminate most human errors an d reduce extraneous sublimation losses during the measurement process. The heat transfer coefficient, which is often desired, can be readily determined from the measured mass transfer results with good confiden ce via a heat/mass transfer analogy. However, this method cannot gener ally be used in certain flow situations such as high-velocity flows be cause of recovery temperature effects and natural convection due to th e thermal buoyancy effects of sublimation latent heat.