Heat transfer enhancement of falling film evaporation on a horizontal tube bundle

Falling film evaporators are gaining popularity as substitutes to typical flooded evaporators because of their low refrigerant charge. It is important to form and keep a thin liquid film on the heat transfer surface to ensure their high heat transfer performance. In this study, as a heat transfer enhancement surface, a fine porous surface processed using thermal spray coating was applied to a smooth copper tube with an outer diameter of 19.05 mm. Heat transfer coefficients of falling film evaporation on a single horizontal tube were experimentally evaluated using the HFC-134a refrigerant. The experiments were performed at a saturation temperature of 20 °C with the heat flux ranging from 10 to 85 kW·m−2 and for film Reynolds numbers up to 673. The study aimed to clarify the effect of the coating on the heat transfer characteristics of falling film evaporation. The results revealed that the coating could suppress partial dry out and enhance nucleate boiling in the falling film. The maximum heat transfer enhancement factor was 5.2 in the experimental range. It was further noted that the effect of the coating was especially strong under a low heat flux condition.

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Numerical Simulation of the Liquid Flowing and Heat-Transfer outside the Tube of the Horizontal-Tube Falling Film Evaporator

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.614-615.296 ◽

2012 ◽

Vol 614-615 ◽

pp. 296-300 ◽

Cited By ~ 1

Author(s):

Wei Kang Hu ◽

Li Yang ◽

Lei Hong Guo

Keyword(s):

Heat Transfer ◽

Horizontal Tube ◽

Water Desalination ◽

Falling Film ◽

Transfer Enhancement ◽

Film Evaporation ◽

Film Evaporator ◽

Spray Density ◽

Performance Of Heat Transfer ◽

Falling Film Evaporation

This paper mainly studies the falling film evaporator in the field of water desalination. Using the method of fluent simulates the process of the liquid flowing and heat-transfer on the horizontal-tube falling film evaporation. The author analyses the distribution of the liquid film, and obtain the rule that spray density, evaporation temperature, temperature difference and pipe diameter affect the performance of heat-transfer in a certain range. So the paper plays a guiding role in heat transfer enhancement in the falling film evaporator.

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Falling Film Evaporation of Water on Horizontal Configured Tube Bundles

2010 14th International Heat Transfer Conference, Volume 4 ◽

10.1115/ihtc14-22536 ◽

2010 ◽

Cited By ~ 4

Author(s):

Wei Li ◽

Xiaoyu Wu ◽

Zhong Luo

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Transfer Enhancement ◽

Inlet Temperature ◽

Falling Film ◽

Transfer Enhancement ◽

Transfer Coefficients ◽

Film Evaporation ◽

Tube Bundles ◽

Falling Film Evaporation

This paper reports an experimental study on falling film evaporation of water on 6-row horizontal configured tube bundles in a vacuum. Three types of configured tubes, Turbo-CAB-19fpi and −26fpi, Korodense, including smooth tubes for reference, were tested in a range of film Reynolds number from about 10 to 110. Results show that as the falling film Reynolds number increases, falling film evaporation goes from tubes partial dryout regime to fully wet regime; the mean heat transfer coefficients reach peak values in the transition point. Turbo-CAB tubes have the best heat transfer enhancement of falling film evaporation in both regimes, but Korodense tubes’ overall performances are better when tubes are fully wet. The inlet temperature of heating water has hardly any effects on the heat transfer, but the evaporation pressure has controversial effects. A correlation with errors within 10% was also developed to predict the heat transfer enhancement capacity.

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