Tubular heat exchanger

A tubular heat exchanger comprising a housing, upper and lower perforated sheet metal plates mounted on the housing, a vertical stack of tubes surrounded by a chamber within the housing, said tubes being mounted adjacent their ends to the upper and lower plates through the perforations, a layer of heat-and acid-sensitive casting resin sealing the tube ends to the upper plate, inlet and outlet means on the housing for flowing a first fluid medium in a vertical direction through the stack of tubes, inlet and outlet means on the housing for flowing a second fluid medium through the chamber surrounding the tube stack, said second fluid medium being at an elevated temperature and including constituents that may cause corrosion of the casting resin layer, and means for preventing thermal and corrosive damage to the casting resin layer, said damage-preventing means comprising a further plate-like member located between the upper and lower metal plates and spaced from the said upper metal plate containing the casting resin to form a space therebetween, said further plate-like member and the said space functioning to separate the second medium from the casting resin and protect the latter from thermal and corrosive damage, inlet and outlet means on the housing for the said space between the upper metal plate and the further plate-like member, and means to supply a third fluid medium to the space inlet means for flowing the third medium through and cooling the said space, said third fluid medium being at a higher pressure than the pressure within the chamber, said further plate-like member comprising two plates with a layer of acid- and heat-resistant material sandwiched therebetween.