Heat Exchanger Configuration & Material Composition
I would recommend either T316 or T321 SS construction for continuous salt-water or fresh water applications. While it is true that the thermal conductivity of brass/copper is better than SS, the performance of a identically-sized and designed exchanger will be impacted by 5-6%.
Keep in mind however, that most heat exchangers sized for jacketwater cooling should be padded for the heatload tolerance specified by the dealer - for GM it is +/- 5%, for CAT is is +/- 8-10% depending on the engine model number.
So, I would not worry about thermal performance comparisons between a SS and brass exchanger. I would design around life cycle of the unit. In either case, the use of a zinc anode would help extend the life of either SS or brass exchanger.
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Regarding configuration..
If engine room is plentyfull, a shell & tube design is prefereable. I would run the JW circuit through the shell side (treated 50/50 prop/glycol mix) and run the raw untreated water through the tubes. Try to size the unit into a single-pass design so that the tubes can be cleaned with a pipe cleaner without removing the end bonnets.
If engine room is limited, a plate & frame exchanger is the way to go. They offer 45% more exchanging surface area than a comperable-footprint S&T (thus making the exchanger footprint much smaller), however are more costly and do offer a easy cleaning solution (if the internals get fouled by the raw cooling water).
I hope this helps..
Ted K.
Philadelphia, PA
