Abstract: A multitubular heat exchanger mainly used in thermal and nuclear power plants having a plurality of tube bundles located within a shell and including a large number of U-shaped heat transfer tubes for permitting a medium to be heated to flow therethrough, and a vent tube interposed between the tube bundles and arranged in the longitudinal direction of the shell, further includes at least one flow guide plate with or without at least one slit disposed in or near the outer marginal portion of one of the tube bundles for inducing streams of a heating medium to flow toward the vent tube. The provision of the guide plate with or without the slit has the effect of moving a heating medium stagnating zone, which has hitherto been located in one of the tube bundles, to a position which is in the vicinity of the vent tube to thereby prevent corrosion of the heat transfer tubes by noncondensable gas.

Abstract: The feedwater heater of this invention comprises a plurality of heating tubes arranged in U form, with feedwater being passed therethrough, a feedwater inlet chamber having a feedwater inlet for introducing feedwater thereinto and a tube plate assembling the ends of said heating tubes and also having formed therein a feedwater reservoir, a feedwater outlet chamber having a feedwater outlet for discharging the heated feedwater and a tube plate assembling the other ends of said heating tubes and also having formed therein a feedwater reservoir, a first cylindrical body or shell having disposed therein a tube nest consisting of the U-formed heating tube portions positioned on one side as well as support plates holding said heating tubes in position, said cylindrical body having its one end communicated with said feedwater outlet chamber and also provided with a hot steam inlet for introducing hot steam that serves as the feedwater heating source, a second cylndrical body or shell having disposed therein a tube n