Heat flow characteristics of Titanium elliptical low rib groove tube with outer falling film evaporation
In order to improve the heat transfer efficiency of the falling film evaporator with a titanium elliptical low rib trans-verse groove tube,the heat flow characteristics of the liquid film flow outside the tube were numerically simulated with the el-lipse coefficient E being in the range of 1.0 to 2.0.The results show that,there are different degrees of the dry patches out-side the tube.The liquid film is significantly thicker near the dry patches than in other areas,and the liquid film coverage is the highest when the value of E is 1.2.The liquid film spreads slower in both of the axial and circumferential directions.The liquid film̍s velocity at the upper of the tube decreases abruptly between Z∗=-0.25～-0.375 and 0.25～0.375 when E is 1.0 and 1.8,and the changing trend of liquid film̍s thickness along the axial direction from the position directly below the spray nozzle to the far end of the spray nozzle decreases firstly and then increases.The maximum heat transfer coefficient in-creases with the increase of E.The tube wall has the highest heat transfer coefficient at the junction between the liquid film and the dry patches,and the average heat transfer coefficient increases and then decreases.Compared to the round tube,the average heat transfer coefficient increases by 34.5%and 15.7%when E is 1.2 and 2.0,respectively.The distribution of vapor-holdup in the tank is opposite to that of the liquid film.The overall vapor-holdup of the liquid film firstly increases and then decreases with the increase of E,and the difference between the average vapor-holdup inside and outside the tank in-creases with the increase of E.
Titanium elliptical low rib transverse groove tubefalling film evaporationellipse coefficientliquid film distri-butionvapor-holdup
国家科技期刊平台
NSTL
万方数据
维普
