Study On The Properties Of Some Key Equipment In The Ocean Thermal Energy Conversion System

Energy has been paid attention to by China and all other countries,which is the material basis of the whole human society.However,the energy structure in China cannot meet the request of the society with the rapid economic development,and it is very urgent to find new energy sources.The ocean thermal energy conversion(OTEC)stands out from many new energy sources as a kind of renewable and clean energy without pollution.The OTEC has not been commercial although its concept was put forward in 1881,and the reason lies in the lack of thorough study of its key equipment.Therefore,some fundamental study of the heat exchanger and the expander was performed in this dissertation,which are two key equipment in OTEC.The results of this study will be of great significance to the application of OTEC.The flow characteristics of pulsatile flow with the same oscillatory fraction in grooved channels of heat exchanger were studied.Firstly,some experiments were done to study the flow characteristics,and some parameters,such as the mean flow rate,the oscillatory fractions,the strokes of the piston pump,the overall pressure drop and local pressure were analyzed.Other experiments with different Reynolds number were performed at the same time;secondly,numerical investigations were done by appropriate model and boundary conditions,and the distribution of wall shear stress and flow streamlines were analyzed,which will be very useful for the design and optimization of high performance heat exchanger.The scroll expander was chosen as the power machine in OTEC system,and was numerically investigated.Firstly,some simple thermodynamic calculation of the thermal system was conducted to determine the conditions of inlet and outlet;secondly,the scroll expander was modeled and the numerical simulation employed with the dynamitic mesh technique was performed by using the ideal gas as the working fluid.Then the distribution of speed field and temperature field were discussed,and the torque and output power were calculated;finally the performance of the scroll expander with different conditions was studied,and the effect of some parameters on the output characteristics were analyzed,such as the revolution speed,the inlet pressure and so on.