Of R134a Spiral Boiling Heat Transfer Simulation Study

Because of its higher heat transfer efficiency, compact in structure and ease to manufacture, helical tubes are widely used as vapor generators and heat exchangers in energy, power plants, chemical and nuclear reactor industry, etc. Because of the complexity of two-phase flow and short of the micro-knowing and quantitative analysis of the heat and mass transfer and dynamical action on the interface of the vapor and liquid phases, boiling heat transfer in helical tubes become a key subject of two-phase. It is of significant importance in both theoretical research and practical applications.Because CFC refrigerants used in refrigerators have the quick destruction of the ozone layer in the outer atmosphere around the earth, new types of refrigerants with zero ozone-depleting potential are needed. R134a is currently considered to be the main replacement to CFC-12. The ODP is zero, the GWP is 0.26, not ease to burn, no poisonous, no corrosive, and it has been used in industry. It is of significant importance to research the boiling of R134a in helical tubes in both theoretical research and practical applications.Based on the experiments of others, this paper presents a three-dimensional model for the saturated bubbly boiling flow of R134a in a vertical tube and helical tubes using the commercial-available CFD software. It enhances the understanding of the saturated bubbly boiling heat transfer in a vertical tube and helical tubes. The model accounts for the detail of temperature, velocity and the void fraction, and these parameters vary along the flow. The results show that the numerical simulation can simulate bubble boiling heat transfer in vertical orientation of helical tubes well, vertical orientation of helical tubes can enhance the boiling heat transfer well. Then the influence of mass flow rate, heat flux and coil diameter ratio on bubble boiling heat transfer in vertical orientation of helical tubes is given. The results can be used as a...