Heat exchanger differential thermal expansion

The contact resistance is also affected by differential thermal expansion when the surfaces are at elevated temperatures or with large temperature differences in the two materials. The problem is aggravated by thermal cycling, especially if one material is heated above its elastic behavior range, and must be considered with finned tubes in air-cooled heat exchangers. 

The complete design of an IHX must consider thermal and hydraulic performance, accommodations for differential thermal expansion, provision for maintenance, and fabrication. As such, the physical configuration of the unit plays a significant role in the performance, reliability, maintainability, and economics of a heat exchanger. 

Thermal Expansion Railroad tracks grow longer in the heat of the sun. The hot tubes in an exchanger grow more than the cold shell. Hence, we have a floating head in the tube bundle to accommodate differential rates of thermal expansion between the tube bundle and the shell. 

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