Falling film evaporation on enhanced tubes, part 1: Experimental results for pool boiling, onset-of-dryout and falling film evaporation

2012 ◽  
Vol 35 (2) ◽  
pp. 300-312 ◽  
Author(s):  
Marcel Christians ◽  
John Richard Thome
Keyword(s):  
Pool Boiling ◽  
Experimental Results ◽  
Falling Film ◽  
Film Evaporation ◽  
Enhanced Tubes ◽  
Falling Film Evaporation

Horizontal-Tube Falling-Film Evaporation With Structured Surfaces

1989 ◽  
Vol 111 (2) ◽  
pp. 518-524 ◽  
Author(s):  
M.-C. Chyu ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
High Flux ◽  
Falling Film ◽  
Structured Surfaces ◽  
Film Evaporation ◽  
Falling Film Evaporation

Extensive experimental tests for tubes with commercial structured surfaces in a horizontal single-tube falling-film evaporator were conducted. The test sections were hollow copper cylinders with GEWA-T, Thermoexcel-E, or High Flux surfaces electrically heated by inserted cartridge heaters. A smooth surface cylinder was also tested for reference. All tubes were tested in both pool boiling and falling-film evaporation with water. The results reveal that falling-film evaporation provides much higher heat transfer coefficients than pool boiling in the low heat flux, convective region. The GEWA-T surface enhances heat transfer through its increased and accessible area, while Thermoexcel-E and High Flux demonstrate high heat transfer performances because of enhanced nucleate boiling. The falling-film evaporation data for the structured surfaces either merge or show a tendency to merge with the respective pool boiling curves at high heat fluxes. Unusual incipient boiling behavior of Thermoexcel-E and the effects of factors such as surface aging, surface subcooling, film flow rate, liquid feed height, and rate of heat flux change, are described.

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