Basic Research On The Separation Process Of Non-condensable Gas In Brine Under Heating

Seawater desalination can change the current situation of lack of fresh water in China.Seawater desalination has different technology directions,among which lowtemperature multi-effect seawater desalination technology has been widely used because of its easy operation and cost saving characteristics.In the heating process of seawater,non-condensable gases(mainly CO2,N2,O2,etc.)will affect heat and mass transfer,so in-depth study of non-condensable gas separation process is of great value for accurate calculation of the process of heat and mass transfer in seawater desalination and the development of related fields.In this paper,the basic research on separation of non-condensable gas in the heating process of pure water,brine and seawater was carried out.Firstly,based on the solubility formula of non-condensable gas in pure water and brine,the UDF function was compiled by Fluent software,and the VOF model was used to simulate the movement of gas-liquid interface,the heating process of pure water and brine containing non-condensable gas was simulated.Then,the types,solubility and enthalpy of the non-condensable gases in seawater were consulted,the main gases studied in this simulation were determined by calculation,the separation of non-condensable gas in the heating process of seawater was carried out by numerical simulation.The simulation results were analyzed,the growth and disappearance of bubbles at different wall temperature and salinity were observed during the heating process of pure water and brine,and the states of bubbles at different times were summarized.Meanwhile,the volume distribution nephogram,temperature nephogram,volume fraction and the separation rate of non-condensable gas during the heating process of pure water and brine were analyzed.The basic law of non-condensable gas separation during the heating process was summarized.On this basis,the characteristics of non-condensable gas bubbles and the effect of separation process on heat transfer were studied,the bubble size and floating speed of non-condensable gas bubbles were analyzed,by drawing the curves of heat transfer coefficient under different conditions and comparing with the phenomenon of non-condensable gas separation,the influence of non-condensable gas bubbles separation on heat transfer was studied.It lays a foundation for further study on the effect of non-condensable gas bubbles on the heat and mass transfer in the process of low-temperature multi-effect seawater desalination.The work done in this paper provides help for further optimize the low-temperature multi-effect seawater desalination technology and calculate the heat and mass transfer process accurately,It also lays a foundation for the development of related fields such as refrigeration,aerospace engineering,so that the phenomenon of the non-condensable gas separation can be better understood and grasped in engineering practice.