Investigations On The Performance Of Direct Contact Condensation Of Steam Jet With Air

Direct contact condensation of steam jet has a high heat and mass transfer efficiency and has been widely applied in the field of energy and power industry.It is very important to reveal the phenomenon of direct contact condensation of steam jet so as to improve the safety and stability of the equipment.At present,it is impossible to obtain the details of the flow field through experiments.Numerical simulation has become an effective method to remedy this shortcoming.Based on the above background,the air immersed jet,pure steam submerged jet and air-steam immersed jet are simulated by CFD method.The VOF multiphase flow model is used to capture and reconstruct the interface in the air-immersed jet.The development process of air-immersed jet under different immersion depth is simulated.The dimensionless analysis method is used to analyze the penetration depth of air jet and the empirical correlation of dimensionless penetration depth is established.In addition,the fast Fourier transform(FFT)method is used to analyze the pressure and velocity oscillation characteristics.This paper adopts the mixture multiphase flow model with two resistance model to simulate the condensation of pure steam submerged jet into cold water,and the influence of the water temperature,the nozzle diameter,spraying direction,and double nozzle on the steam jet condensation has been studied.Besides,the steam jet plume length and gas-liquid interfacial heat transfer coefficient and flow field parameters are analyzed.The result of research shows that the simulation of mixture multiphase flow model with two-thermal-resistance model can be applied to steam condensation of submerged jet.The gas compression and expansion waves exist in steam plume core area.There is the peak pressure at the tail end of steam plume.With the increasing of nozzle diameter,the peak may be greater than the outlet pressure.With the increasing of water temperature and entrance pressure,the dimensionless gas plume length will also increase.In order to be able to take the effect of air into account,the pure steam jet condensation model is modified in order to simulate the condensation phenomenon of steam jet with air.The influence of different inlet pressure is simulated by using mixture multiphase flow model and modified condensation model,and the distribution of parameters in the convection field is also analyzed.Simulation results show that the whole jet region can be divided into two phase flow regions according to the velocity field distribution,which are the steam core region and the air-water turbulent jet flow zone,and the existence of air will lead to the enhancement of the diffusion degree of the jet process.