In this work, the easy to use, simple and direct equations were formulated and tested. These equations can be used to calculate the mean values of the heat transfer coefficients of inside tube flow during phase change...In this work, the easy to use, simple and direct equations were formulated and tested. These equations can be used to calculate the mean values of the heat transfer coefficients of inside tube flow during phase change. Analytical and experimental methods were used to correlate these equations. Two different forms were used, one for evaporation case and the other for condensation case. Carbon dioxide, CO2, was used as case study. Correlated values of the mean heat transfer coefficients （hcor,.） were compared with the experimental results （he^e） and with other published result, a good agreement was noticed. The resulted correlations can be used to simplify the design and performance studies of both condensers and evaporators.展开更多
The visualization experiments on HFC R410A condensation in a vertical rectangular channel （14.34mm hydraulic diameter, 160mm length） were investigated. The flow patterns and heat transfer coefficients of condensatio...The visualization experiments on HFC R410A condensation in a vertical rectangular channel （14.34mm hydraulic diameter, 160mm length） were investigated. The flow patterns and heat transfer coefficients of condensation in the inlet region were presented in this paper. Better heat transfer performance can be obtained in the inlet region, and flow regime transition in other regions of the channel was also observed. Condensation experiments were carried out at different mass fluxes （ from 1.6 kg/h to 5.2 kg/h） and at saturation temperature 28~ C. It was found that the flow patterns were mainly dominated by gravity at low mass fluxes. The effects of interfacial shear stress on condensate fluctuation are significant for the film condensation at higher mass flux in vertical flow, and con- sequently, the condensation heat transfer coefficient increases with the mass flux in the experimental conditions, The drop formation and growth process of condensation were also observed at considerably low refrigerant vapor flow rate.展开更多
文摘In this work, the easy to use, simple and direct equations were formulated and tested. These equations can be used to calculate the mean values of the heat transfer coefficients of inside tube flow during phase change. Analytical and experimental methods were used to correlate these equations. Two different forms were used, one for evaporation case and the other for condensation case. Carbon dioxide, CO2, was used as case study. Correlated values of the mean heat transfer coefficients （hcor,.） were compared with the experimental results （he^e） and with other published result, a good agreement was noticed. The resulted correlations can be used to simplify the design and performance studies of both condensers and evaporators.
基金supported by National Natural Science Foundation of China(No.51176008)National Key Technology R&D Program(2012BAB12B02)
文摘The visualization experiments on HFC R410A condensation in a vertical rectangular channel （14.34mm hydraulic diameter, 160mm length） were investigated. The flow patterns and heat transfer coefficients of condensation in the inlet region were presented in this paper. Better heat transfer performance can be obtained in the inlet region, and flow regime transition in other regions of the channel was also observed. Condensation experiments were carried out at different mass fluxes （ from 1.6 kg/h to 5.2 kg/h） and at saturation temperature 28~ C. It was found that the flow patterns were mainly dominated by gravity at low mass fluxes. The effects of interfacial shear stress on condensate fluctuation are significant for the film condensation at higher mass flux in vertical flow, and con- sequently, the condensation heat transfer coefficient increases with the mass flux in the experimental conditions, The drop formation and growth process of condensation were also observed at considerably low refrigerant vapor flow rate.
