Heat exchanger

A heat exchanger, comprising a tube bundle having a plurality of rows of tubes adapted to be arranged successively in the direction of air flow therepast, an inlet header for introducing vapor into one end of the tubes of the rows, a plurality of outlet headers each for receiving condensate and uncondensed vapor from the opposite ends of the tubes of one of said rows, each outlet header having an outlet from the lower end thereof, a generally upright drain pot having an upper portion which surrounds said outlets, a plurality of leg seal tubes each connecting with the outlet from one of the outlet headers and extending into a lower portion of the drain pot, means for maintaining the level of condensate within the drain pot above the lower ends of the leg seal tubes so as to isolate pressures within said outlet headers from one another, and an additional tube connecting one outlet header above its lower end with the drain pot above the condensate level therein so as to introduce uncondensed vapor from said one outlet header into said drain pot.