Optimization Design And Performance Analysis For Desalination System On Ship With Vertical Tube Climbing Film Evaporator

Water is the source of life and an indispensable basic substance for human survival and production.With the growth of population and the rapid development of industry and agriculture,human beings are facing the dilemma of shortage of fresh water resources.Increasing the supply of fresh water through seawater desalination has become an effective way to solve this problem.With the development of navigation industry and people's exploration of the ocean,the research on ship seawater desalination technology has received extensive attention.In this thesis,facing the complex and changeable environment of the ocean,seawater desalination system with vertical tube climbing film evaporator is designed.According to the balance of mass and energy,the mathematical models of the evaporator,the condenser are established,which considers the temperature loss caused by flow resistance of vapor and seawater boiling point elevation.Under the condition that seawater physical property is a function of temperature and concentration,and water vapor and saturated water physical property are a function of temperature,the program of climbing film seawater desalination system in vertical tube evaporator is written by C language,a method through the principle of Equal-area combined Iteration Algorithm used to solve the program has been developed.Based on the results of simulation calculation,analyzes the variation of thermodynamic performance with the number of evaporator,the temperature of heating steam in the first effect,the temperature of generated steam in the last effect and concentration ratio.It is proposed to optimize the system performance by installing TVC and preheater.Also,it is established the mathematical models of the preheater,the desuperheater and the thermal vapor compression(TVC).The mathematical model is solved by simulation.Through the comparison and analysis of different configuration,it is concluded that TVC and preheater can effectively increase the performance ratio(PR),reduce the specific cooling seawater flow and specific area.Because the performance change of TVC makes the influence trend of the temperature of heating steam in the first effect and the temperature of generated steam in the last effect on the PR and specific cooling seawater flow of the system larger.At the same time,when seawater is preheated by the generated steam and the condensed water in first evaporatortogether,PR is the largest,while seawater is preheated by generated steam in first evaporator alone,specific area and the specific cooling seawater flow are the smallest.Installation of TVC and preheating of seawater can effectively improve the thermodynamic performance of the system and the cost of water production.Finally,the research on the influence of the pressure of motive steam on the thermodynamic performance of the system shows that the pressure increases,the PR increases,the specific area and the specific cooling seawater flow decrease.