Study On Heat And Mass Transfer Characteristics Of Diffusion-Gap Distillation

Fresh water resources on the earth is very few,and the spatial distribution is uneven.China has a large population,and the total amount of freshwater resources is small.Per capita freshwater resources are only 1/4 of the world average,and it is one of the 13 countries with the lowest per capita water resources in the world.Using seawater desalination technology to separate fresh water from seawater is the most effective way to solve the problem of the shortage of freshwater resources.The development and application of seawater desalination technology in China have a certain gap compared with developed countries.The development of seawater desalination has received more and more attention.The diffusion-gap seawater desalination method described in this paper is a thermal separation method.The device has the advantages of large surface area,low operating temperature,good heat source adaptability,low metal consumables,normal pressure operation,etc.It is very suitable for applications in remote mountainous areas and island areas,and has a very good development prospect.In this paper,the diffusion-gap seawater desalination is modeled and analyzed.First,a mathematical model is established by the conservation of mass and energy,and the thermal performance of the process is analyzed by MATLAB simulation.Analyze the thermal performance of the process,including the effect of hot fluid temperature,cold fluid temperature,flow rate,solution concentration,air gap width,and model height on the freshwater yield and Gain Output Ratio.Then we get the distribution of temperature and thermal resistance in the height direction.Finally,the heat transfer,heat radiation,and thermal convection between evaporator and condenser are compared.In order to verify the use of power of this process,the exergy analysis was done using NaCl aqueous solution model.Sensitivity analysis of the exergy efficiency was performed with the hot fluid temperature,cold fluid temperature,solution concentration,and air gap width.Then calculate and compare the external heat source,evaporator,air gap,and condenser exergy losses in the process.Finally,analyze the influence of changes in operating conditions on the exergy damage of air gap components.Using Fluent to simulate the water vapor diffusion process in the air gap by adding UDF,get the distribution of temperature,pressure,water vapor concentration,velocity and evaporation rate in the air gap,it is conducive to know the microscopic flow within the air gap.