Methods based on local linearization of rigorously posed heat and mass balances are developed which yield the system states explicitly at points along the length of a partial condenser. Equations are presented for co-current, counter-current and mixed flow operation for one component vapor-gas mixtures. It is also shown that the nonlinear model equations can be readily solved by means of standard equation solving procedures. Numerical experiments indicate good agreement between solutions of the nonlinearized and locally linearized heat and mass balance equations for the air water vapor system investigated.