The objective of this study is optimization of OTEC system using double fluted tube type heat exchanger including turbine configuration parameters and comparison of the performance of OTEC plant using plate type heat exchanger and one using double fluted tube type. The results of this study show the plate type heat exchanger has several advantages and it can be compact. The optimization parameters were the velocity of cold and warm sea water passing through the heat exchangers, the phase change temperature, and turbine configuration parameters such as specific speed, specific diameter and ratio of blade to diameter.
Ocean Thermal Energy Conversion (OTEC) is a system of converting heat energy into electricity by using temperature difference between the surface water and the depth. The working fluid is evaporated using warm seawater and is condensed using cold seawater. Since the temperature of warm sea water is small (about 30°C). The working fluid with a low boiling point has to be selected. Ammonia and Freon 22 have been indicated as suitable working fluids for OTEC according to the studies carried out by Uehara et al. An OTEC plant with ammonia as working fluid has several advantages in comparison with an OTEC plant with Freon 22 as working fluid by Uehara and Nakaoka (1984a) (1984b). Further, Freon 22 usage has been restricted since it cause for disruption of the Ozone layer. Therefore ammonia is selected as working fluid in this paper. High performance heat exchanger should be used in evaporator and condenser since the utilizable temperature difference is small (about 20°C). It is generally said that the plate type heat exchanger and the double fluted tube type one are suitable for OTEC power plant. Uehara et al studied the optimization of OTEC using the plate type heat exchanger and the double fluted tube type one (Uehara and Nakaoka (I 984b) and Uehara et al (1989).
