Yetholm-type shield of dots. The artist could not hope to show the fine detail of a Yetholm-type shield, but the similarity is striking. The impressive shields would have indicated high social status. The shields are made of a copper alloy sheet about 0.6 mm thick. The alloy is a high-tin bronze: copper with 11-14% tin. They are round with a central domed boss created by hammering out from the back. The shield face is covered in raised ridges in concentric rings, each a couple of millimetres high. Between the ridges are rings of small hemispherical bosses about 4 mm across. Decoration was
Copper in heat exchangers titanium. This article focuses on beneficial properties and common applications of copper in heat exchangers. New copper heat exchanger technologies for specific applications are also introduced. Heat exchangers using copper and its alloys have evolved along with heat transfer technologies over the past several hundred years. Copper condenser tubes were first used in 1769 for steam engines. Initially, the tubes were made of unalloyed copper. By 1870, Muntz metal, a 60% Cu-40% Zn brass alloy, was used for condensers in seawater cooling. Admiralty metal, a 70% Cu-30% Zn yellow brass alloy with 1% tin added to improve corrosion resistance, was