The design of heat exchangers in the advanced supercritical power conversion system cannot be separated from the study of heat transfer issues.Half-side heating mode is often encountered for solar receiver and supercr...The design of heat exchangers in the advanced supercritical power conversion system cannot be separated from the study of heat transfer issues.Half-side heating mode is often encountered for solar receiver and supercritical boiler.Here,the characteristics of supercritical CO_(2)(sCO_(2))convection heat transfer in vertical tubes with circumferentially half-side heating was numerically investigated through the SST k-ωturbulent model which matches well with the experimental data.Then,heat transfer between sCO_(2)upflow and downflow was compared.Similar to film boiling heat transfer at subcritical pressure,numerical results were processed according to the supercritical pseudo-phase transition hypothesis,with liquid-like phase in the tube core region and vapor-like film in the region near the heated tube wall.The structure of two layers was demarcated by pseudo-critical temperature T_(pc).Therefore,sCO_(2)heat transfer was assessed according to double thermal resistances caused by vapor-like film near the wall and core liquid-like phase.The findings suggest that wall temperature for upflow is higher than that for downflow,which is attributed to larger thermal resistance in the fluid domain for upflow than that for downflow.The difference guarantees the excellent heat transfer performance for downflow than upflow.It is also further concluded that the formation of vapor-like film near the wall due to pseudo-phase transition plays a key role in dominating wall temperature and inducing heat transfer deterioration in half-side heating tubes.The present contribution is significant to the design of supercritical heat exchanger under half-side heating mode.展开更多
基金supported by Science and Technology Research Projects of the Education Department of Jilin Province(No.JJKH20230116KJ)Doctoral Scientific Research Funds for Northeast Electric Power University(No.BSJXM-2021214)Natural Science Foundation of Jilin Province of China(No.20230101341JC)。
文摘The design of heat exchangers in the advanced supercritical power conversion system cannot be separated from the study of heat transfer issues.Half-side heating mode is often encountered for solar receiver and supercritical boiler.Here,the characteristics of supercritical CO_(2)(sCO_(2))convection heat transfer in vertical tubes with circumferentially half-side heating was numerically investigated through the SST k-ωturbulent model which matches well with the experimental data.Then,heat transfer between sCO_(2)upflow and downflow was compared.Similar to film boiling heat transfer at subcritical pressure,numerical results were processed according to the supercritical pseudo-phase transition hypothesis,with liquid-like phase in the tube core region and vapor-like film in the region near the heated tube wall.The structure of two layers was demarcated by pseudo-critical temperature T_(pc).Therefore,sCO_(2)heat transfer was assessed according to double thermal resistances caused by vapor-like film near the wall and core liquid-like phase.The findings suggest that wall temperature for upflow is higher than that for downflow,which is attributed to larger thermal resistance in the fluid domain for upflow than that for downflow.The difference guarantees the excellent heat transfer performance for downflow than upflow.It is also further concluded that the formation of vapor-like film near the wall due to pseudo-phase transition plays a key role in dominating wall temperature and inducing heat transfer deterioration in half-side heating tubes.The present contribution is significant to the design of supercritical heat exchanger under half-side heating mode.
