Preliminary Study On Problems Related To Low Pressure Evaporation Of Seawater Containing Non-condensable Gas

Desalination technology is an important technical means to solve the shortage of freshwater resources in China.Among the many desalination methods,low-temperature multi-effect evaporation desalination has become the main technical direction of China's desalination projects,with significant technical advantages and economic value.In the low-temperature multi-effect evaporation process of seawater,the non-condensable gas(mainly oxygen,nitrogen,carbon dioxide,etc.)has an important influence on heat and mass transfer,so the basic phenomenon of evaporation and the evaporation of brine and its non-condensable gas under low pressure The study of solubility has important research value for improving the calculation and analysis methods of low-temperature multi-effect seawater desalination and developing corresponding high-tech.Based on the research of low-temperature multi-effect seawater desalination,this paper is funded by the low-pressure evaporation research project containing non-condensable gas brine.The preliminary basic problems related to the numerical simulation of pure water evaporation and the experimental design of salt water non-condensable gas solubility test under low pressure.Were studied.The main contents are as follows:In this paper,from the two aspects of numerical simulation method and experimental scheme design,the design of pure water evaporation simulation and the experimental scheme of salt water non-condensable gas solubility test under low pressure were carried out.In terms of numerical simulation,starting from the pure water evaporation process,the Fluent software was used to simulate the evaporation boiling process of pure water using the VOF model.The phase transition process customizes the UDF function between water and water vapor.The phenomenon of bubble formation,growth and overflow under different initial temperature conditions is summarized and summarized.Four typical models of bubble motion during evaporation are summarized.State,and studied the basic heat transfer law of pure water evaporation and bubble motion at different temperatures.After comparing the water vapor volume fraction distribution cloud map,temperature cloud map,pressure cloud map and water vapor volume fraction distribution and mass flow rate during the evaporation process of pure water,the basic theoretical law of pure water phase change evaporation is obtained.And an explanation of the internal mechanism of the precipitation change.At the same time,the design of the experimental scheme for the solubility test of non-condensable gas in brine under low pressure was carried out.According to the purpose and requirements of the experiment,the data of dissolved non-condensable gas in seawater was consulted.It was determined that the design of this experiment mainly studied the carbon dioxide,nitrogen and oxygen in the water.The change of temperature and pressure content and the influence on heat transfer determine the experimental principle and experimental scheme,clarify the experimental steps,and draw the schematic diagram of the solubility test of salt water non-condensable gas according to the experimental principle and experimental scheme.The required experimental equipment was determined from the schematic and the main equipment(gas chromatograph,double-layer glass reactor)was introduced.The numerical simulation and experimental scheme design work done in this paper,in order to further explore the influence of brine evaporation and non-condensable gas under low pressure on heat and mass transfer process,reveal the essential laws of seawater desalination and evaporation process under low pressure conditions,and lay a certain The foundation can be better applied to engineering practice.