Theoretical and Experimental Study on Secondary Heat Recovery Cycle System of Mixed Working Fluid for Ocean Thermal Energy Conversion

Due to the small temperature difference available in the ocean thermal energy conversion (OTEC) system and the low power generation efficiency, searching for high-efficiency thermal cycle has always been an important research aspact in this field. This study constructed a thermodynamic cycle of OTEC with non-azeotropic mixed working fluid, added the secondary heat recovery of the dilute solution branch, performed theoretical analysis and numerical calculation. The relationship between cycle efficiency and parameters such as working fluid concentration, turbine inlet pressure and extraction factor was obtained. The results showed that the cycle thermal efficiency can reach up to 5.25%. A 10 kW secondary heat recovery OTEC system was built, and the system performance under stable operation conditions was obtained. The efficiency of the power generation system is up to 3.8%, and the heat transfer coefficients of the evaporator and condenser under this heat transfer condition were obtained, which provides basic data and technical support for its engineering application.