The surface of capillary wall can be treated to have a periodic microrelief mathematically. The roughness is micro enough compared with the thickness of the liquid film. So, the surface roughness only exerts influence...The surface of capillary wall can be treated to have a periodic microrelief mathematically. The roughness is micro enough compared with the thickness of the liquid film. So, the surface roughness only exerts influence on the adsorptive potential. Macroscopically, the flow field of the liquid film can be considered as that when the rough surface has an equivalent smooth surface, whose position is at the crests of the microrelief. The mechanism of heat transfer is in connection with two resistances: the thermal resistance of the liquid film conduction and the thermal resistance of the interfacial evaporation. The capillary pressure between the two sides of the vapor-liquid interface due to the interfacial curvature and the disjoining pressure owing to the thin liquid film are considered simultaneously. Several micro tubes with different micro rough surfaces are studied. The length of the evaporating interfacial region decreases with the increase of roughness angle and/or the increase of the roughness height. The heat transfer coefficient and the temperature of the vapor-liquid interface will change to fit the constant mass flow rate.展开更多
Experimental investigations of boiling heat transfer from porous suffaces at atmospheric pressure were performed. The porous surfaces are plain tubes covered with metal screens, V-shaped groove tubes covered with sc...Experimental investigations of boiling heat transfer from porous suffaces at atmospheric pressure were performed. The porous surfaces are plain tubes covered with metal screens, V-shaped groove tubes covered with screens, plain tubes sintered with screens, and V-shaped groove tubes sintered with screens.The experimental results show that siatering metal screens around spiral V-shaped groove tubes can greatly improve the boiling heat transfer. The boiling hysteresis was observed in the experiment. This paper discusses the mechanism of the boiling heat transfer horn those kinds of porous surfaces stated above.展开更多
A new model has been developed to predict the capillary limit of axial-grooved heat pipe.In the model the concepts of liquid saturation or liquid fraction of the cross-sectional area of groove,the modified relative pe...A new model has been developed to predict the capillary limit of axial-grooved heat pipe.In the model the concepts of liquid saturation or liquid fraction of the cross-sectional area of groove,the modified relative permeability,absolute permeability of groove and Leverrt’s function are used.The Leverrt’s function is well represented by the function f（s）=(1/51/2)（1/s-1）0.175.In the model the effects of gravitational force,capillary force and viscous force are considered.The calculated results are in good agreement with existing experimental data reported in the literature.展开更多
A model was established to predict condensation heat transfer coefficient on horizontal rectangular-finned tube. Drop-Off zone at the tube bottom was considered and determined, the known Honda(and owen) expression of ...A model was established to predict condensation heat transfer coefficient on horizontal rectangular-finned tube. Drop-Off zone at the tube bottom was considered and determined, the known Honda(and owen) expression of retention angle was also modified as a result of considering drop-off zone.Heat flux on fin tips in the unflooded region, fin fianks, fin spacings and fin tips in the flooded regionwere analyzed respectively. Condensation on fin tips is emphasized by considering the variation of filmthickness along circumference as well as horizootally. Fin efficiency was considered in calculation. Theprediction results were compared with several researchers’ experimental data for three kinds of workingfluids on seven different tube geometries and for various temperature differences. These data underabout 60 test conditions were predicted with discrepancy of ±10%. Prediction by the present modelfor steam and R-113 condensation were compared with previous models.展开更多
基金NationalNW Sdence Foundation of China with the fort No.59995550-4 and the POst-doctoral FOundation. Thesupports are gIatef
文摘The surface of capillary wall can be treated to have a periodic microrelief mathematically. The roughness is micro enough compared with the thickness of the liquid film. So, the surface roughness only exerts influence on the adsorptive potential. Macroscopically, the flow field of the liquid film can be considered as that when the rough surface has an equivalent smooth surface, whose position is at the crests of the microrelief. The mechanism of heat transfer is in connection with two resistances: the thermal resistance of the liquid film conduction and the thermal resistance of the interfacial evaporation. The capillary pressure between the two sides of the vapor-liquid interface due to the interfacial curvature and the disjoining pressure owing to the thin liquid film are considered simultaneously. Several micro tubes with different micro rough surfaces are studied. The length of the evaporating interfacial region decreases with the increase of roughness angle and/or the increase of the roughness height. The heat transfer coefficient and the temperature of the vapor-liquid interface will change to fit the constant mass flow rate.
文摘Experimental investigations of boiling heat transfer from porous suffaces at atmospheric pressure were performed. The porous surfaces are plain tubes covered with metal screens, V-shaped groove tubes covered with screens, plain tubes sintered with screens, and V-shaped groove tubes sintered with screens.The experimental results show that siatering metal screens around spiral V-shaped groove tubes can greatly improve the boiling heat transfer. The boiling hysteresis was observed in the experiment. This paper discusses the mechanism of the boiling heat transfer horn those kinds of porous surfaces stated above.
基金supported by the National Science Foundation of China
文摘A new model has been developed to predict the capillary limit of axial-grooved heat pipe.In the model the concepts of liquid saturation or liquid fraction of the cross-sectional area of groove,the modified relative permeability,absolute permeability of groove and Leverrt’s function are used.The Leverrt’s function is well represented by the function f（s）=(1/51/2)（1/s-1）0.175.In the model the effects of gravitational force,capillary force and viscous force are considered.The calculated results are in good agreement with existing experimental data reported in the literature.
文摘A model was established to predict condensation heat transfer coefficient on horizontal rectangular-finned tube. Drop-Off zone at the tube bottom was considered and determined, the known Honda(and owen) expression of retention angle was also modified as a result of considering drop-off zone.Heat flux on fin tips in the unflooded region, fin fianks, fin spacings and fin tips in the flooded regionwere analyzed respectively. Condensation on fin tips is emphasized by considering the variation of filmthickness along circumference as well as horizootally. Fin efficiency was considered in calculation. Theprediction results were compared with several researchers’ experimental data for three kinds of workingfluids on seven different tube geometries and for various temperature differences. These data underabout 60 test conditions were predicted with discrepancy of ±10%. Prediction by the present modelfor steam and R-113 condensation were compared with previous models.
