Numerical Investigation Of Subcooled Flow Boiling In Rectangular Narrow Channel With OpenFOAM

Subcooled flow boiling is widely existing in various industrial processes.The flow boiling in narrow channels has the characteristics of high heat transfer efficiency and it has important applications in nuclear reactors.Because of the influence of scale effect,the flow boiling phenomenon in the narrow channel is different from the characteristics of the wide channel.However,the models used to describe wall heat transfer in many CFD programs are established based on pool boiling experiments in wide channels,which cannot be applied to flow boiling calculation in narrow rectangular channels.Considering these situations,this paper studied the models related to the two-fluid equation,analyzed the heat transfer characteristics of the heated wall of the narrow channel,and provided a theoretical basis for the similar numerical analysis.so the numerical study of two-phase flow was carried out.by the way of using two-fluid model in Open FOAM and DEDALE air-water two-phase flow experiment,the interfacial force models under low bubble fraction was analyzed.It is found that the Ishii-Zuber drag model,Tomiyama lift model,FAD turbulent diffusion force model and Tomiyama wall lubrication force model can be applied to the numerical calculation of two-phase flow under the condition of low bubble fraction.The influence of narrow rectangular channel size is considered,and the wall nucleation model in wide channel is modified by using the experimental data of narrow rectangular channel.the modified wall nucleation model can better predict the bubble departure diameter,departure frequency,nucleation site density and other parameters.Then we implanted the modified wall boiling model into the two-fluid model of Open FOAM platform and carried out numerical analysis of the experimental conditions,got reasonable results.In this paper,a series of numerical analysis of subcooled boiling in a narrow rectangular channel is carried out.The research shows that when the heating wall heat flux is constant,the heating area of the wall will affect the two-phase flow parameters such as temperature field and velocity field in the channel,but have little effect on the wall nucleation parameters and the distribution of wall heat flux.For the narrow rectangular channel undercooled boiling experimental section in the numerical study of this paper,with the increase of inlet subcooling degree and mass flow rate,the proportion of evaporation heat flux and quenching heat flux decreases,and the proportion of single-phase convective heat flux increases The increase of power will promote the quenching heat transfer and evaporation heat transfer between the wall and the fluid.The heat flux of convective heat transfer increases first and then decreases with the increase of power.