This document contains test results for different tube materials used in heat exchangers. It provides heat transfer coefficients and generator output values for Admiralty steel tubes, stainless steel, titanium, and other materials at varying circulation water inlet temperatures. Simulation results show that below 70°F there is virtually no change in generator output between materials, but above 70°F stainless steel and titanium perform better than Admiralty steel, with up to a 2 MW lower output for Admiralty steel between 80-90°F.