This study performed second-law analysis on saturated FC - 22 vapor flowing through and condensed in horizontal cooling tubes. An optimum Reynolds number existed over the parametric range investigated for the single tube case at which the entropy generated at a minimum rate. For the multi-tube cases, on the other hand, no optimal Reynolds number was identified subject to constant surface-area constraint. Furthermore, there was an optimal cooling temperature that: generated a minimum of entropy for a given duty. The present phase-change system was inherently different in thermodynamic performance from the single-phase convective system intensively discussed in literature works.