Heat transfer to gas turbine blades occurs at high Reynolds numbers, therefore in thin boundary layers. This makes the measurement of local heat transfer coefficients or Nusselt numbers difficult and suggests to measure mass transfer coefficients or Sherwood numbers instead. These are then transformed to Nusselt numbers by the heat/mass transfer analogy. The present paper extends this analogy to processes in which the Schmidt number for mass transfer is not equal to the Prandtl number for heat transfer, by use of general fluid mechanics and transfer relations for boundary layers and explores what equations for the analogy can be derived in this way. The results are compared with computational and experimental information.