No corrosion margin is considered for the heat exchange tubes
Thread Content
Why is no corrosion margin considered for heat exchange tubes?
Heat exchange element: thickness affects the heat exchange process. Heat exchange tubes are vulnerable components that can be replaced, so a corrosion margin is not considered.
1. “\"Ignoring corrosion margin for heat exchangers\" – this is an extremely incorrect statement ； 2. It is up to the owner to decide whether to consider corrosion margin or not ； 3. If the medium is corrosive, the designer should alert the owner.
There should be some margin; for example, for a 20-grade steel heat exchange tube with a diameter of 25 mm and a pressure of 25 kg/cm2, the calculated wall thickness is less than 0.3 mm. Under normal circumstances, a tube with a wall thickness of 2.5 mm is chosen, providing at least a 2-mm margin.
The heat exchange tubes are replaceable components, and excessive corrosion margin may affect heat transfer efficiency
I really didn’t notice that. I was wondering, under which standard did you see it?
Item e) of 4.4.5.4 in GB/T151-2014.
1. Heat exchange tubes are primarily used for heat transfer. If corrosion allowance is taken into account, overly thick tube walls hinder heat transfer and have a significant impact on the efficiency of heat exchange. 2. The selection of heat exchange tubes takes into account the corrosivity of the medium from the initial design stage; therefore, the material choice is crucial. 3. In heat exchanger design, the thickness is generally not chosen based on the strength of the heat exchange tubes; for example, the calculated thickness might be 0.5 mm, but the actual wall thickness used will definitely be much greater than 0.5 mm.
The last edit to this post was made by wiseboy on 2016-12-3 at 08:17. “The selection of heat exchange tubes took into account the corrosiveness of the medium during the initial design phase” – so it was indeed taken into consideration! Moreover, material selection is also taken into consideration during design! The manufacturer has no right to change the wall thickness or material on its own.