1305089 Tubular heat exchangers for cooling gases SCHMIDT'SCHE HEISSDAMPF GmbH 4 March 1970 [5 March 1969] 10436/70 Heading F4S Parallel rows of spaced apart closed-end return tubes together form a tube bundle and some at least, have their jacketing tubes connected to one another by longitudinal fins or ribs 9, the tube ends in adjacent rows being disposed in stepwise manner as shown in Fig. 1. In use, cracked or other synthesized hot gas flows over the tubes between coned inlet and outlet heads 11, 12 into which the tubes extend; and a coolant such as water flows into the tubes via headers 13, Fig. 2 and connecting tubes 6, and exits from the tubes as a steam-water emulsion, via tubes 7 and headers 14. The central portion 16 of a casing containing the tubes is lined with heat insulating material. The casing ends 15, 17 are filled with heat insulating material and gas leakage at the inlet end is prevented by a seal plate 21 and a sand seal 24 provided by a skirt 20 extending from the plate 21. Further sealing is provided by a body 25 of heat insulating material above the plate 21.