a shell and tube heat exchanger particularly of enhanced diameter size of use , particularly , in the manufacture of sulfuric acid and having a plurality of an adjacent pair of longitudinal baffle plates located symmetrically and intermittently between and extending the length of the tube bundle . the exchanger is most advantageously made from segments which may be shipped to off - site locations for in situ manufacture of the heat exchanger , particularly when oversized heat exchangers are required when transportation of such large heat exchangers from an off - site manufacturing facility is not possible .