Abstract
Ocean thermal energy conversion (OTEC) has attracted attention as a technique to obtain renewable energy. OTEC systems usually use a plate heat exchanger and ammonia as a working fluid. The materials used for manufacturing the heat exchanger are generally “titanium” or “stainless steel” of which contact surface should not be corroded with ammonia. However, the thermal conductivity of these materials is very low. Consequently, the heat transfer performance of the heat exchanger deteriorates. Therefore, the author proposed an advanced plate heat exchanger material with high thermal conductivity for OTEC systems. This plate is made of an aluminum alloy and the surface is coated with a special high polymer material (PEEKTM polymer), which has high ammonia resistance. In this study, two tolerance experiments were performed using the advanced plate at different coating thicknesses of 300 and 20 μm for approximately one month. These experiments were (1) immersion of the plate in a pressure tank containing liquid ammonia and (2) exposure of the plate in the path of a forced convective flow of liquid ammonia. As a result, although the PEEK coating aluminum plate surface deteriorated slightly, it is found that the base of the plate has not influenced by the ammonia.
