Study On The Exchenger Of The Otec Desalination System

Water and energy are two important resources which are essential for the development of modern society. With the rapid development of the modern industry, the demand for fresh water increased sharply, an important way to solve the problemof fresh water is seawater desalination, while the conventional seawater desalination methods, such as distillation, ion exchange, dialysis, reverse osmosis, and freezing, have to consume a large amount of energy, and consumption of large quantities of fossil fuels has caused serious environmental problems.Ocean thermal energy conversion can save energy and solve fresh water problems at the same time.However,the available temperature difference of the ocean thermal energy is very small,so a heat exchanger which is suitable for small temperature difference is required to improve the efficiency of the ocean thermal energy desalination.The paper designed a desalination system which is attached to ocean thermal energy conversion,choosing bare tube and finned tube heat exchangers. Studied the performence of two heat exchangers and the fresh water yield of the system in the same condition.The main contents are as following:(1)Designe ocean thermal energy desalination system, design or select equipments,then builds the experiment platform,determine experiment schemes.(2)Analyze various parts of the condensation heat transfer outside the tube.Introduct the basic theory of the heat transfer computation,giving the coefficient of convection heat transfer in and out the tube and the total heat transfer coefficient, also derive the theoretical calculation formula of the fresh water yield.(3)According to the heat and mass transfer performence of the condesation heat transfer,with the reasonable assumptions,the physical and mathematical model of the two heat exchanger are established using CFD.For the condition of existing phase change,the UDF file is imported into the solver,obtain the temperature and velocity profile and heat transfer coefficient relation curve(4)Do experiment using the system,to the flow and temperature of the warm and cool water, fix three of the four factors and change another,and compare the finned tube heat exchanger system and the bare tube heat exchanger system.