Numerical Simulation Of Fluid Flow And Heat Transfer Of The Plate Falling Film Evaporator

Plate falling film evaporator is a kind of new highly efficient heat exchange equipment,By using the principle of falling film evaporation mass transfer to drive the heat transfer to improve the heat transfer effect,and has broad prospects in the fields of petroleum,chemical industry and sea water desalination.Because the outer plate falling film evaporation is a complicated heat and mass transfer process,and the lack of the in-depth understanding on the process of falling film evaporation.Therefore,study on the heat and mass transfer characteristics have very stronger necessity and practical significance.Based on the basic theory of fluid mechanics the and the numerical simulation method,this paper using the VOF model in the fluid mechanics simulation software FLUENT?First of all,the use of user defined function(UDF)method to define the liquid phase at the interface of the evaporation effect establish plate type falling film evaporation 2D simulation model,Preliminary study on the effects of different conditions on the heat transfer performance,by numerical simulation to obtain the main research contents:(1)improve the reasonable temperature and liquid phase entrance wall heat flux,can improve the corresponding interface temperature,enhanced evaporation effect,improve heat transfer performance;(2)increase the inlet air flow rate and reduce the liquid inlet flow rate can be enhanced evaporation heat transfer,improve the heat transfer efficiency of the evaporator,but choose the suitable liquid inlet flow rate and air inlet velocity.Then on this basis to define the flow and heat transfer characteristics of gas relative film shearing force and surface tension effect of the source to established two-dimensional corrugated plate falling film evaporation simulation model,get the following conclusion:(1)corrugated siding face greater influence of flow field in corrugated depressions gas velocity is relatively small,The velocity of liquid phase is more and more downward velocity under the action of gravity;(2)in the process of liquid film flowing down,the liquid phase of the inlet part of the liquid film thickness is larger,and with the flow,the thickness of the liquid film decreases;(3)the temperature distribution and the heat and mass transfer effect are all due to the fluctuation of the ripple;(4)in the horizontal direction,the temperature is gradually reduced,and in the liquid phase and gas phase,the change of gradient is first large and small,and the temperature near the interface changes,but the temperature change rate is not continuous;(5)improve the wall heat flux and reduce the air relative humidity,improve the air inlet velocity,the increase of liquid phase inlet temperature and flow rate can promote liquid evaporation effect,but improve the evaporation rate does not necessarily indicates that its heat transfer performance is improved.Based on the above research,Preliminary simulation study on the factors affecting the flow and heat and mass transfer performance of the falling film evaporator,deepen the understanding of the liquid film flow and heat transfer process in the actual falling film evaporation equipment,and to provide theoretical guidance for improving the heat transfer efficiency in practical industrial applications.