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Vendors information for humidified gas/flue gas interchangers

Q: I am looking for potential vendors/types for a humidified gas/flue gas interchanger for cooling flue gas from 1,000ºF to 900ºF and heating humid gas from 200ºF to 940ºF for total duties of 0.13mm Btu/h. We have purchased Sumitomo plate-fin exchangers in the past, but have had mixed results with sort life from thermal cycling. Would you recommend any other types, potential vendors or resources to look for alternatives? I also have a downstream heat exchanger that further cools flue gas to 200ºF by making tempered water at 250ºF.

A: Plate fin exchangers that are subjected to thermal stress due to steep temperature gradients often fail at the brazed joints. Thermal cycling will do the same thing over time. The style of heat exchanger that is appropriate for this service is highly dependent upon the details of the process gases to which you refer and the pressure drop that can be tolerated. Basic choices include shell and tube, plate, spiral and finned economizer bundles — vendors for these styles of exchangers can be found with a simple web search or by utilizing a manufacturers list such as Thomas Register (American Manufacturers). Other resources for heat exchanger design include “Process Heat Transfer” by Hewitt, Shires and Bott; “Heat Exchangers Selection, Rating and Thermal Design” by Kakac and Liu.