Boiling process and a heat exchanger for use in the process

In a process for the separation of air into its constituent components, wherein the separation is carried out in a cryogenic distillation column system comprising at least one distillation column, wherein a nitrogen-rich fluid stream is heat exchanged against an oxygen-enriched liquid stream thereby at least partially vaporizing the oxygen-enriched liquid stream by means of a heat exchanger designed to maintain no more than a small temperature difference between the oxygen-enriched liquid stream and the nitrogen-rich fluid stream, wherein the heat exchanger comprises a parallelpipedal body formed by an assembly of parallel vertical extending passages having generally vertical corrugated fins therein, wherein the oxygen-enriched liquid stream is introduced into a first group of passages and the nitrogen-rich fluid stream is introduced into a second group of passages constituting the remaining passages, and wherein the oxygen-enriched liquid stream is distributed at the top of and throughout the horizontal length of the first group of passages, the improvement for enhanced performance comprises:

• (a) establishing and maintaining a fixed volume distribution zone containing hardway finning disposed above the vertical corrugated fins in the first group of passages;
• (b) passing the oxygen-enriched liquid stream downwardly and over the hardway finning at a rate such that at least twenty five percent (25%) of the available volume of said distribution zone is in the liquid phase;
• and
• (c) passing the oxygen-enriched liquid stream downwardly over the generally vertical corrugated fins in the first group of passages as a thin film and controlling the oxygen-enriched liquid stream flow at a rate to maintain a local liquid film Reynolds number of at least 20 but not greater than 1000 throughout the upper seventy five percent (75%) of the generally vertical corrugated fins.