In order to realize steady-state operation of the neutral beam injection（NBI） system with high beam energy,an accurate thermal analysis and a prediction about working conditions of heat-removal structures inside hig...In order to realize steady-state operation of the neutral beam injection（NBI） system with high beam energy,an accurate thermal analysis and a prediction about working conditions of heat-removal structures inside high-heat-flux（HHF） components in the system are key issues.In this paper,taking the HHF ion dump with swirl tubes in NBI system as an example,an accurate thermal dynamic simulation method based on computational fluid dynamics（CFD） and the finite volume method is presented to predict performance of the HHF component.In this simulation method,the Eulerian multiphase method together with some empirical corrections about the inter-phase transfer model and the wall heat flux partitioning model are considered to describe the subcooled boiling.The reliability of the proposed method is validated by an experimental example with subcooled boiling inside swirl tube.The proposed method provides an important tool for the refined thermal and flow dynamic analysis of HHF components,and can be extended to study the thermal design of other complex HHF engineering structures in a straightforward way.The simulation results also verify that the swirl tube is a promising heat removing structure for the HHF components of the NBI system.展开更多
This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass ...This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.展开更多
It is a key factor to increase heat transfer coefficien t of high viscosity fluid in the shell side for making a high performance cooler.T he heat transfer and flow resistance performance of trapezoid fin tube high vi...It is a key factor to increase heat transfer coefficien t of high viscosity fluid in the shell side for making a high performance cooler.T he heat transfer and flow resistance performance of trapezoid fin tube high visc osity fluid cooler with helical or segmental baffles were studied, and compared with the heat transfer coefficient of low-fin-tube cooler with segmental baffl es. Experimental results indicated that heat transfer film coefficient in the sh ell side of trapezoid fin tube cooler with entire helical baffles was 60% more h igher than that of low-fin-tube cooler with segmental baffles,and pressure dr op was lower by 40%. Heat transfer film coefficient in the shell side of trapezo id fin tube cooler with entire helical baffles was 20% more higher than that of trapezoid-fin tube cooler with segmental baffles, and pressure drop was lower b y 50%.Heat transfer film coefficient in the shell side of trapezoid fin tube coo ler with entire helical baffles was 10% higher than that of trapezoid fin tube c ooler with sectional helical baffles, and pressure drop was lower by 19%.Heat tr ansfer film coefficient in the shell side of trapezoid fin tube cooler with segm ental baffles was 30% more higher than that of low-fin-tube cooler with segmen tal baffles, and pressure drop remained unchanged.展开更多
基金supported by the Special Program of ITER(International Thermonuclear Experimental Reactor)in China(No.2013GB101002)
文摘In order to realize steady-state operation of the neutral beam injection（NBI） system with high beam energy,an accurate thermal analysis and a prediction about working conditions of heat-removal structures inside high-heat-flux（HHF） components in the system are key issues.In this paper,taking the HHF ion dump with swirl tubes in NBI system as an example,an accurate thermal dynamic simulation method based on computational fluid dynamics（CFD） and the finite volume method is presented to predict performance of the HHF component.In this simulation method,the Eulerian multiphase method together with some empirical corrections about the inter-phase transfer model and the wall heat flux partitioning model are considered to describe the subcooled boiling.The reliability of the proposed method is validated by an experimental example with subcooled boiling inside swirl tube.The proposed method provides an important tool for the refined thermal and flow dynamic analysis of HHF components,and can be extended to study the thermal design of other complex HHF engineering structures in a straightforward way.The simulation results also verify that the swirl tube is a promising heat removing structure for the HHF components of the NBI system.
文摘This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.
文摘It is a key factor to increase heat transfer coefficien t of high viscosity fluid in the shell side for making a high performance cooler.T he heat transfer and flow resistance performance of trapezoid fin tube high visc osity fluid cooler with helical or segmental baffles were studied, and compared with the heat transfer coefficient of low-fin-tube cooler with segmental baffl es. Experimental results indicated that heat transfer film coefficient in the sh ell side of trapezoid fin tube cooler with entire helical baffles was 60% more h igher than that of low-fin-tube cooler with segmental baffles,and pressure dr op was lower by 40%. Heat transfer film coefficient in the shell side of trapezo id fin tube cooler with entire helical baffles was 20% more higher than that of trapezoid-fin tube cooler with segmental baffles, and pressure drop was lower b y 50%.Heat transfer film coefficient in the shell side of trapezoid fin tube coo ler with entire helical baffles was 10% higher than that of trapezoid fin tube c ooler with sectional helical baffles, and pressure drop was lower by 19%.Heat tr ansfer film coefficient in the shell side of trapezoid fin tube cooler with segm ental baffles was 30% more higher than that of low-fin-tube cooler with segmen tal baffles, and pressure drop remained unchanged.
