I want to design a heat exchanger which will operate in salty water. I want to know what material is corrosion resistant and has good thermal conductivity.
Hi,
to answer your question properly the service temperature range for your system would be a great hint. Could you refer on that?
Kindly
Michael
What Michael schymura said is correct...
In addition to that, S31803 offers higher strength and, therefore, lighter weight components for the same applications as 316 and can additionally be used up to 60çC in wet exhaust systems and in fully submersed applications (particularly, heat exchanger application...)
Ref: "Corrosion Resistance in Marine Environments", Australian Stainless magazine - Issue 6, October 1996.
Austenitic stainless steel (316 etc) would definitely be a bad idea as it is susceptible to pitting and crevice corrosion and stress corrosion cracking in chloride solutions. If cost is no object I would recommend titanium, otherwise you should look at the materials used for seawater condensers (mostly copper-based alloys).
@ Robert
I agree with you, but SS316 can offer a nominal protection considering the material cost. Further improvements could be obtained with the use of protective coatings which would ultimately lead to cost effective solution rather than to go for Ti- or Cu- based alloys.
Coatings present heat transfer barriers, but steel sacrificial elements could provide cathodic protection of stainless steel (but needs expert design).
Bob
Careful selection of coating composition and depositon technique could eliminate the problem of heat transfer barrier
Harpreet
Possibly, but coatings are not generally used for heat exchangers, and I doubt if such a solution would be available 'of the shelf'.
Stainless steel will not bear salty water for long time .
Any other which has good conductivity?
Proper brass alloy would be better for heat exchanger because of better heat transfer compared to AISI 316 (with 2 - 3 % of Mo).
You may find the required information about corrosion resistance at Table 28-2 entitled "General Corrosion Properties of Some Metals and Alloys" at: R.H. Perry, D.W. Green, J.O. Maloney (Eds.), "Perry’s Chemical Engineers’ Handbook", 7th ed., McGraw-Hill, 1997. Selected thermal conductivity data for metals and alloys can be found at this same reference (Tables 2-374 to 2-376).
There are some papers for cpt critical pitting temperature for NiMo alloys, that could help.
Cu-Ni (90/10 or 60/40) both are good for seawater heat exchanger's tubing..
AISI 316L stainless steel is excellent and costs a lot more than the 304 because it has elements in the alloy that makes it much more resistant to marine corrosion.
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