Numerical analyses on the feasibility of TC type nozzles in ocean thermal energy Conversion turbines

The turbine is a crucial component in harnessing ocean thermal energy (OTE), and the impact of the nozzle on turbine performance is significant. TC-profile nozzles have been proven to operate efficiently in air turbines under high-temperature and high-pressure conditions. However, their performance in ocean thermal energy conversion (OTEC) turbines using organic working fluids (low-temperature and low-pressure) still requires further research. Therefore, we focused on a practical 100 kW OTEC turbine equipped with different types of TC-profile nozzles. Three-dimensional numerical models were established, and the simulation results demonstrated that the turbine efficiency using TC-3A was generally higher than other turbines, reaching an optimal efficiency of 89.4%. The turbine can operate efficiently at deviations from the design point of + 10.27% or -31.39% in mass flow rate, +/- 3 degrees C in inlet temperature, and + 20% or -11.43% in rotor speed during off-design conditions. The results revealed the adaptability of TC-3A nozzles to the OTEC environment and their excellent off-design performance. The study could provide valuable guidance and references for the application of TC-type nozzles in the field of OTEC turbines.