27 for the baffles 28 indicated as longitudinally spaced in transverse configuration to and surrounding the tubes 23 of the tube bundle 22 the top tube sheet 24 is interposed between the top shell flange 16 and the first flange member 18 of the elbow member 12 seal members 29 such as flat annular gaskets are interposed between the top tube sheet 24 and the top shell flange 16 and between the tube sheet 24 and the first flange 18 of the elbow member 12 to provide a fluid tight seal and isolate the fluid passing exterior to the tube bundle 22 from the fluid passing interior to the tubes 23 of the bundle 22 the flange members 16 and 18 with the tube sheet 24 are removably attached together for example with a plurality of bolts 30 and nuts 31 in fig1 and more better illustrated in fig2 there is shown the bottom tube sheet 25 connected to the bottom elbow member 13 in a sealing relationship a washer like peripheral plate member 32 is interposed between the bottom shell flange 17 and the first flange member 20 of the bottom elbow member 13 the plate member 32 radially extends a predetermined length toward the center axis of the shell member 11 forming a flat ledge portion 33 with a shoulder 34 for supporting the bottom tube sheet 25 and providing a mating surface for a seal member 37 the bottom tube sheet 25 is removably attached to the ledge portion 33 for example with a plurality of bolts 35 and nuts 36 the seal member 37 such as an annular flat gasket is provided betwen the tube sheet 25 and the ledge portion 33 to provide a fluid tight.