Abstract: This disclosure teaches a heater which is especially well suited to handling large flows of a process stream at low pressure losses. A cylindrical sleeve, having a first end and a second end, is mounted by means of a bellows in a cylindrical shell having a first end and a second end each corresponding with that of the sleeve. The first ends converge to form a convection input passage therebetween, the second ends diverge to form a radiant zone therebetween. Hot gas passes between the shell and the sleeve through the radiant zone and then the convection input zone, the process stream passes through the inner flow space. A baffle is mounted within the sleeve in its first end to channel the process stream into a convection output passage boardered inwardly by the baffle and outwardly by the sleeve. Extended surface projects from the sleeve into the convection input zone and additional extended surface projects from the sleeve into the convection output passage.

Abstract: This disclosure teaches a heater which is especially well suited to handle large flows of a process stream at low pressure losses. A cylindrical sleeve is mounted by means of a bellows inwardly of a cylindrical shell to separate an inner hot gas flow space from an annular outer process flow space. The sleeve encloses an entrance combustion zone and has an exit end. A baffle is mounted inwardly of the sleeve with a closed end projecting into the exit end of the sleeve to channel the hot gas into an annular convection space bordered outwardly by the sleeve. Extended surface projects from the sleeve into the process flow space and additional extended surface projects from the sleeve into the convection space.