Flow boiling heat transfer of nitrogen at high subcritical pressure conditions in a single vertical mini-channel with the diameter of 2.0 mm was experimentally investigated.The tested mass flux varied from 530 to 830 ...Flow boiling heat transfer of nitrogen at high subcritical pressure conditions in a single vertical mini-channel with the diameter of 2.0 mm was experimentally investigated.The tested mass flux varied from 530 to 830 kg/(m^2·s),the inlet pressure ranged from 630 to 1080 kPa,and the heat flux ranged from 0 to 223.2 kW/m^2.Effects of the mass flux and the inlet pressure on the nitrogen boiling curve were examined.Results showed that within the limited test conditions,the merging of three boiling curves indicates the dominance of nucleate boiling and the inlet pressure has a positive enhancement on heat transfer performance.Three heat transfer trends were identified with increasing heat flux.At low heat fluxes,the heat transfer coefficient increases first and then decreases with vapour quality.At intermediate heat fluxes,the heat transfer coefficient versus the vapour quality presents an inverted"U"shape.At high heat fluxes,a double valley shape was observed and the partial dry-out in intermittent flow and annular flow helps to interpret the phenomenon.The increasing inlet pressure increases the heat transfer coefficient over a wide range of vapour quality until the partial dry-out inception.The lower surface tension and lower latent heat of evaporation enhance the nucleate boiling for higher inlet pressure.A modified experimental correlation(mean absolute error(MAE)=19.3%)was proposed on the basis of the Tran correlation considering both the nucleate boiling and the partial dry-out heat transfer mechanism.展开更多
Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher perfo...Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher performance of a rocket engine. The theoretical model is complicated, it relates to fluiddynamics, heat transfer, combustion, etc... In this papers a regenerative cooling model is presented.Effects such as radiation, heat transfer to environment, variable thermal properties and coking areincluded in the model. This model can be applied to all kinds of liquid propellant rocket engines aswell as similar constructions. The modularized computer code is completed in the work.展开更多
Endothermic hydrocarbon fuel is regarded as an optimal fuel for a scramjet with regenerative cooling,which provides extra cooling through endothermic chemical conversion to avoid the severly limited cooling capacity w...Endothermic hydrocarbon fuel is regarded as an optimal fuel for a scramjet with regenerative cooling,which provides extra cooling through endothermic chemical conversion to avoid the severly limited cooling capacity when conventional fuels are adopted for cooling.Although endothermic cooling is proposed from the view point that the heat sink of a conventional fuel is insufficient,the heat-absorbing through endothermic chemical reaction is actually a chemical recuperation process because the wasted heat dissipated from the engine thermal structure is recovered through the endothermic chemical reaction.Therefore,the working process of a scramjet with endothermic hydrocarbon fuel cooling is a chemical recuperative cycle.To analyze the chemical recuperative cycle of a chemically recuperated scramjet engine,we defined physical and chemical recuperation effectivenesses and heating value increment rate,and derived engine performance parameters with chemical recuperation.The heat value benefits from both physical and chemical recuperations,and it increases with the increase in recuperation effectiveness.The scramjet performance parameters also increase with the increase in chemical recuperation effectiveness.The increase in chemical recuperation effectiveness improves both the performances of the fuel cooling system and the combustion system.The results of analysis prove that the existence of a chemical recuperation process greatly improves the performance of the whole scramjet.展开更多
基金the National Natural Science Foundation of China(No.11872373)。
文摘Flow boiling heat transfer of nitrogen at high subcritical pressure conditions in a single vertical mini-channel with the diameter of 2.0 mm was experimentally investigated.The tested mass flux varied from 530 to 830 kg/(m^2·s),the inlet pressure ranged from 630 to 1080 kPa,and the heat flux ranged from 0 to 223.2 kW/m^2.Effects of the mass flux and the inlet pressure on the nitrogen boiling curve were examined.Results showed that within the limited test conditions,the merging of three boiling curves indicates the dominance of nucleate boiling and the inlet pressure has a positive enhancement on heat transfer performance.Three heat transfer trends were identified with increasing heat flux.At low heat fluxes,the heat transfer coefficient increases first and then decreases with vapour quality.At intermediate heat fluxes,the heat transfer coefficient versus the vapour quality presents an inverted"U"shape.At high heat fluxes,a double valley shape was observed and the partial dry-out in intermittent flow and annular flow helps to interpret the phenomenon.The increasing inlet pressure increases the heat transfer coefficient over a wide range of vapour quality until the partial dry-out inception.The lower surface tension and lower latent heat of evaporation enhance the nucleate boiling for higher inlet pressure.A modified experimental correlation(mean absolute error(MAE)=19.3%)was proposed on the basis of the Tran correlation considering both the nucleate boiling and the partial dry-out heat transfer mechanism.
文摘Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher performance of a rocket engine. The theoretical model is complicated, it relates to fluiddynamics, heat transfer, combustion, etc... In this papers a regenerative cooling model is presented.Effects such as radiation, heat transfer to environment, variable thermal properties and coking areincluded in the model. This model can be applied to all kinds of liquid propellant rocket engines aswell as similar constructions. The modularized computer code is completed in the work.
基金supported by the National Natural Science Foundation of China (General Program) (Grant No. 51106037)the Distinguished Young Scholars (Grant No. 50925625)the Innovative Research Groups(Grant No. 51121004)
文摘Endothermic hydrocarbon fuel is regarded as an optimal fuel for a scramjet with regenerative cooling,which provides extra cooling through endothermic chemical conversion to avoid the severly limited cooling capacity when conventional fuels are adopted for cooling.Although endothermic cooling is proposed from the view point that the heat sink of a conventional fuel is insufficient,the heat-absorbing through endothermic chemical reaction is actually a chemical recuperation process because the wasted heat dissipated from the engine thermal structure is recovered through the endothermic chemical reaction.Therefore,the working process of a scramjet with endothermic hydrocarbon fuel cooling is a chemical recuperative cycle.To analyze the chemical recuperative cycle of a chemically recuperated scramjet engine,we defined physical and chemical recuperation effectivenesses and heating value increment rate,and derived engine performance parameters with chemical recuperation.The heat value benefits from both physical and chemical recuperations,and it increases with the increase in recuperation effectiveness.The scramjet performance parameters also increase with the increase in chemical recuperation effectiveness.The increase in chemical recuperation effectiveness improves both the performances of the fuel cooling system and the combustion system.The results of analysis prove that the existence of a chemical recuperation process greatly improves the performance of the whole scramjet.
