Experimental And Numerical Simulation Study On Separation Efficiency Of Corrugated Plate Dryer

As a secondary separation device in the natural circulation steam generator of pressurized water reactor nuclear power plants,the performance of the corrugated plate dryer directly affects the quality of the steam at the outlet of the steam generator.Currently,research on corrugated plate dryers mainly focuses on cold state experiments.However,the separation process under hot state operating conditions is more complex than that under cold state conditions.Therefore,in order to obtain more accurate experimental laws,it is necessary to analyze the correlation between cold state and hot state parameters.At the same time,due to the complexity of the internal flow field of the corrugated plate dryer during the two-phase separation process,there are limitations to studying it through experimental methods.Numerical simulation methods can better understand the internal flow of the dryer.Therefore,this paper conducts relevant research on the numerical simulation of the transformation relationship between the cold and hot states of the corrugated plate dryer and its separation performance.Therefore,in this paper,the relationship between the critical velocity of corrugated plate dryer and the numerical simulation of the separation performance of corrugated plate dryer has been studied.Firstly,an experimental platform was designed and built to study the separation efficiency of the corrugated plate dryer under hot and cold states.Experimental research was carried out on the effects of different structural parameters(plate spacing,plate type),operating parameters(pressure,inlet velocity),and drainage tank structure on the separation efficiency and critical flow velocity of the corrugated plate dryer,and the differences between hot and cold state conditions were analyzed.It was found that there is a critical plate spacing value,at which the critical flow velocity of the corrugated plate dryer is the largest.When the inlet velocity of the dryer is small,the plate spacing has a greater impact on the separation efficiency of the corrugated plate dryer under hot state conditions than under cold state conditions.For the same plate type,the separation efficiency and critical flow rate under hot state conditions are lower than those under cold state conditions.The influence of the drainage tank height on the separation efficiency under hot and cold state conditions is consistent.Secondly,based on the phenomenon of liquid film rupture in the separation process,a critical flow velocity model for corrugated plate dryers was derived.By combining this model with experimental data,critical flow velocity calculation formulas were fitted for different plate spacings.At the same time,the derived critical flow velocity model was compared with previous models,and three conversion factor equations for critical flow velocity between cold and hot states were summarized.These equations were compared with the conversion coefficients for critical flow velocity in previous hot and cold state experiments.A method was proposed to combine the critical flow velocity model based on liquid droplet rupture with the model based on liquid film rupture.The model established by this method was in good agreement with experimental results,with a maximum relative error of 5.6% between the model calculation results and experimental results.Then,the numerical simulation of the double-hook corrugated plate dryer is carried out which is based on the DPM model coupled with the wall liquid film model.In the calculation,the VOF model is used to calculate the droplet drag force model in the hot state,which is distinguished from the droplet drag force model in the cold state.At the same time,the R-R distribution is selected as the droplet distribution model,and the relevant parameters in the critical velocity model derived in the early stage are used as the critical conditions of the wall liquid film model The numerical simulation results are compared with the experimental results to verify the applicability of the critical velocity model The error between the numerical results and the experimental results is 13.2%,and the separation efficiency deviation is between 4%and 14%.At the same time,the airflow movement in the whole structure of the dryer with drainage tank is numerically simulated,and the influence of drainage tank height on the separation performance of corrugated plate dryer is also studied.Finally,the motion trajectory of liquid droplets was analyzed from the perspective of force balance,and a separation efficiency model for corrugated plate dryers was obtained for both single particle size distribution and non-uniform particle size distribution of liquid droplets.The effect of plate spacing on the separation efficiency of corrugated plate dryers was qualitatively analyzed.