Pelagic seiner Doña Martita, New Bedford, Mass. This ship just had a major refit, including installation of advanced technology R.W. Fernstrum Fishing Vessel Keel Coolers.

Keel coolers are a type of heat exchanger, designed to cool marine engines by conducting heat from engine cooling water through metal tubes or castings to the water floating the ship. The devices are quite sophisticated, reflecting a century of engineering advancements. Leading manufacturers include R.W. Fernstrum, Duramax Marine LLC, Johnson, Walter, and Bowman. Trade names can be non-specific: Fishing Vessel Keel Coolers, fishing vessel heat exchanger, rectangular tube keel cooler, water to water heat exchangers, and 90/10 copper/nickel or marine grade aluminum rectangular tubing. They can also be trade marked or bear otherwise specific names: R.W. Fernstrum Keelcoolers, R.W. Fernstrum gridcooler, Duramax, dura cooler, duracooler, Johnson demountable keel coolers, Bowman Heat Exchangers, WEKA copper/nickel Boxcooler, or WEKA-Fernstrum Boxcooler.