Optimization Calculation And Design Of Ship Plate Thermal Seawater Desalination System

With rapid development of science and technology in 21 th century,human industry and agriculture are inseparable from fresh water resources,causing global freshwater use is fast-growing.First of all,the gradually reduced freshwater resources directly used by people,coupled with uneven distribution of water resources in space and time intensify the contradiction between supply and demand of fresh water.So desalination technology,one of the effective ways to solve the shortage of water resources,have to be mentioned.Moreover,shipping is the most important means of transportation in today's society.During the maritime transportation,fresh water is not only supplied to the ship's machinery but also used by the crew in daily life.Therefore,desalination technology on the ship is also one of the hot issues today.In this paper,we mainly study the single and double effect plate thermal seawater desalination system using the waste heat of the ship.In order to make full use of the low grade thermal energy on the ship,the sleeve cooling water is selected as the heat source of the drive system.Based on the principle of mass conservation and energy conservation,the mathematical model of the thermal process of single and double effect desalination systems is established.The utility model comprises a preheater with a single-effect preheating system,an evaporator and a condenser;and an evaporator and a condenser of the single-double desalination system integrating the preheater in the first effect evaporator.Through the calculation program,the simulation calculation is carried out under the influence of different heat source flow,fresh water production,concentration ratio and amount of cold water on the thermal system performance of the desalination system.Under ship's working conditions in this paper,the calculation results show that the fresh water production of the single-effect preheating system increases with the increase of the heat source water flow,and the change of the heat source distribution ratio will not affect the system's water production ratio.When the amount of feed water is constant,the value of the system concentration ratio increases as the heat source distribution ratio.The heat exchange area of the system evaporator,condenser and preheater increases as the increase of heat source distribution ratio.The total heat exchange area decreases first and then increases with the increase of steam temperature.When the steam temperature is 55 °C,the total heat exchange area is the smallest.The return water temperature of the double-effect desalination system decreases as the first two-effect steam temperature increases,and decreases as the fresh water production increases.When the concentration ratio increases,the return water temperature of the system shows a trend of rapid growth and then slow growth.The reflux flow of concentrated brine increases with the increase of freshwater production,and the concentration ratio increases rapidly and then decreases slowly.The heat exchange area of the evaporator and condenser of the system increases with the increase of fresh water production.The first effect evaporator of the double effect system utilizing fresh water heat has a lower heat exchange burden and a smaller system heat rejection.When the fresh water production is constant,it is concluded that the heat energy consumed by the double-effect system is smaller than that of the single-effect system,and the heat exchange area of the evaporator is larger in the fresh water production,compared with the heat exchange area,heat removal and return water temperature of the single-effect desalination system.At a lower time,less energy is required to extract cold seawater.The research results of this paper provide some design ideas and research basis for the high-efficiency seawater desalination device that involve and optimize the ship.