Experimental study on falling film evaporation characteristics of R-134a outside of a vertical enhanced tube

2021 ◽  
Vol 180 ◽  
pp. 121805
Author(s):  
Tianjiao Zhang ◽  
Liangdong Ma ◽  
Jili Zhang
Keyword(s):  
Experimental Study ◽  
Falling Film ◽  
Film Evaporation ◽  
Enhanced Tube ◽  
Falling Film Evaporation ◽  
R 134A

Effects of Inclination Angle on Falling Film Evaporation Using R-134a

2005 ◽  
Author(s):  
Liang-Han Chien ◽  
Hung-Ta Lin
Keyword(s):  
Heat Transfer ◽  
Inclination Angle ◽  
Falling Film ◽  
Film Evaporation ◽  
Evaporation Heat ◽  
Finned Surface ◽  
Falling Film Evaporation ◽  
Plain Surface ◽  
Evaporation Heat Transfer ◽  
R 134A

This manuscript discusses the effect of inclination angle and surface geometries on the falling film evaporation performance. Falling film evaporation experiments were conducted on a smooth plate and finned plates using refrigerant R-134a at 18 °C system temperature. The plate was inclined with angles between 10° and 40°, and the heat fluxes are between 36 and 73.5kW/m2. The local heat transfer coefficients are measured, and the falling film flow distribution is observed through a sight glass. The test results showed that the falling film evaporation heat transfer coefficient increases as the inclination angle increases or the heat flux increases. The finned surface yields better falling film evaporation heat transfer performance than the smooth surface. The ratio of the heat transfer coefficient of the finned surface versus the plain surface is between 2.5 and 12.4 folds. This ratio increases as the inclination angle increases. The visualization observation showed that bubble nucleation is more pronounced on the finned surface than the plain surface. The effect of boiling on falling film evaporation is discussed.

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