| With the development of society and the improvement of people’s living standards,the shortage of water resources has become a worldwide problem.Desalination is an effective way to solve this problem.High-energetic consumption is one of the main factors restricting the development of desalination.On the one hand,the desalination process requires energy to separate fresh water,and the energy consumption of desalination is relatively high.On the other hand,a large amount of concentrated brine is discharged after desalination.The concentrated brine is usually discharged directly into the sea without treatment.It will definitely affect the environmental and ecological balance of offshore waters.Based on this,my research team proposes an integrated method of desalination and salt production,which transfers the adverse pulsation,which generated by the high-pressure pump during the desalination process of the reverse osmosis membrane method,to the falling film evaporation desalination system and spray drying salt making process,to form the pulsating hot air flow,thereby improving the heat and mass transfer effect of the desalination and saltmaking process.The technology not only eliminates the harmful pulsation in the process of reverse osmosis desalination,but also transforms into the beneficial pulsation in the process of desalination and salt production.In order to achieve the above method,my research team has designed an adaptive-frequency pulsating energy exchanger,to transfer the pulsation to the falling film evaporator or spray drying system,so that harmful pulsation becomes favorable pulsation.The exchanger can improve evaporation and liquid drop crushing and drying efficiency,to achieve double-effect energy saving.In order to optimize the performance parameters of pulsating energy exchanger,and adjust the pulsating parameters for different working conditions,this paper mainly studies the evaporation characteristics of the liquid film or droplets in the pulsating airflow with different parameters,so as to obtain the pulsating airflow parameters under the better evaporation effect,and provides for the development and design of the pulsating energy exchanger.The main research contents and conclusions of this article are as follows:1.Based on the numerical simulation method,the falling film evaporation process is simulated by software Fluent,and the effect of the pulsation on the falling film evaporation of the vertical plate is studied.Aiming at the problem that the pulsating airflow evaporates the falling film of the vertical plate,by establishing a two-dimensional turbulent vertical plate falling film model,and using a triangular wave pulsating airflow to evaporate it,a numerical simulation study is performed.Airflow can enhance the convective mass transfer effect of falling film evaporation.When the relative amplitude A is 5/6 and dimensionless frequency Wo is 26,the pulsating energy exchanger has optimal parameters for the falling film evaporation of the vertical plate.2.Aiming at the effect of pulsating airflow on the evaporation of falling film on the inner wall of a vertical circular tube,by establishing a two-dimensional turbulent droplet model,using triangle wave pulsating airflow to evaporate it,performing numerical simulation research,and analyzing the amplitude and frequency broken effect.And compared with the uniform airflow,the pulsating airflow can enhance the convective mass transfer effect of the vertical circular tube falling film evaporation.When the relative amplitude A is 1/7 and dimensionless frequency Wo is 10,the pulsating energy exchanger can obtain the best evaporation effect in vertical tube falling film.3.In order to explore the optimal frequency and amplitude range of pulsating energy exchangers in droplet breaking,this paper aims at the problem of the impact of pulsating airflow on the breaking of droplets.By establishing a three-dimensional phase-free droplet model,triangle wave pulsating airflow is used to break droplet up.Numerical simulation studies are performed to analyze the impact of amplitude and frequency on the breakup.It is concluded that compared with uniform airflow,pulsating airflow can enhance the effect of droplet breakup.When the relative amplitude A is1 and dimensionless frequency Wo is 96.6,the pulsation energy exchanger has optimal parameters for the breakup of droplets.4.Finally,in view of the effect of phase-change pulsating airflow on droplet evaporation,this paper establishes a three-dimensional droplet model,uses high-temperature pulsating airflow to evaporate the droplet,and conducts numerical simulation studies to analyze the impact of pulsation amplitude and frequency on droplet evaporation.It is found that compared with the uniform velocity airflow,the pulsating airflow can enhance the droplet evaporation effect.The best evaporation effect can be obtained,when the pulsating energy exchanger adjust parameters A=1/5 and Wo=96.6. |
