Experimental Studies on Heat Transfer Coefficients of Horizontal Tube Falling Film Evaporation With Seawater

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Shengqiang Shen ◽  
Xue Chen ◽  
Xingsen Mu ◽  
Changkun Jiang
Keyword(s):  
Heat Transfer ◽  
Horizontal Tube ◽  
Falling Film ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Film Evaporation ◽  
Evaporation Temperature ◽  
Spray Density ◽  
Falling Film Evaporation

The overall heat transfer process in a horizontal tube falling film evaporator is mainly influenced by the falling film evaporation outside horizontal tube due to the average heat transfer coefficient which is about 50% of that of the condensation inside tube. A series of experimental studies were conducted to investigate the heat transfer coefficients of the falling film evaporation outside the horizontal tube with parameters such as the spray density, the evaporation temperature, the salinity, and the tube spacing. Experiments were conducted by using Al-brass tubes with 19 mm outer diameter and 1600 mm length. The horizontal tubes are arranged vertically in the evaporator. The test tube is heated by an internal electric heater with uniform heat flux. Temperatures of the test tube surface and saturated vapor measured by thermocouples are used to calculate the heat transfer coefficients. The seawater with salinity of 1.5%, 3.0%, and 4.5% was used as experimental fluid. The spray density varied between 0.017 and 0.087 kg/(m s), and the evaporation temperature was controlled in the range of 50–70 °C. Results show that the average heat transfer coefficients of water under different salinities increase obviously with the spray density until a certain point. The average heat transfer coefficients of seawater decrease slightly with the evaporation temperature, decrease with the salinity, increase with the tube spacing, and are almost independent of the heat flux. In addition, the comparisons with 25.4 mm outer diameter tube and the circumferential distribution of local heat transfer coefficient are presented in this study.

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

2012 ◽  
Vol 614-615 ◽  
pp. 296-300 ◽  
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.

Investigation of Condensation Heat Transfer on a Tube With Wavy Fins

2019 ◽  
Author(s):  
Tailian Chen
Keyword(s):  
Heat Transfer ◽  
Condensation Heat Transfer ◽  
Falling Film ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Film Evaporation ◽  
Transfer Capability ◽  
Falling Film Evaporation ◽  
Insight Into ◽  
Good Agreement

Abstract In this work, heat transfer coefficient during condensation of a refrigerant on the outside surface of a copper tube with wavy fins was experimentally investigated. To fully characterize the condensation heat transfer, the experiments were conducted under two conditions: no refrigerant overfeed and subject to various degree inundation. The results under the condition of no overfeed are compared with the Beatty and Katz model. While the trend of degradation with increasing subcooling was in good agreement with the model (within 5%), the condensation heat transfer coefficients from the wavy fins were 11–15% higher. Based on the Nusselt model, the surface tension effect is not taken into account in the Beatty and Katz model, which plays an important role in condensation on a surface with fins. The photographs taken during the experiments showed that the condensate dripping columns have a pitch is in agreement with that proposed by Yung et al. [24] for falling film evaporation applications. The second part of the experiments under the various degree of inundation provides further insight into the heat transfer capability of the surface with wavy fins.

A New Model for Predicting Falling Film Evaporation Heat Transfer Coefficients

2016 ◽  
Author(s):  
Apurva Baruah ◽  
Sunil Mehendale
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Design ◽  
Falling Film ◽  
Transfer Coefficients ◽  
New Model ◽  
Heat Transfer Coefficients ◽  
Film Evaporation ◽  
Falling Film Evaporation

For falling film evaporation, the most important considerations from a thermal design standpoint are the onset of film dryout and the local heat transfer coefficients in partially and fully wet conditions. Previous methods developed for the prediction of (i) pool boiling heat transfer coefficient (HTCs), (ii) the onset of dryout, and (iii) falling film heat transfer coefficient consist of empirical, tube-specific constants which are quite difficult, if not impossible, to determine, and hence have limited utility. New methods to predict these parameters have been developed in the present study, which eliminate the special constants by incorporating dimensionless parameters that capture the effect of refrigerant properties and macro-level tube-geometry. The predictions of the new model have been found to be better than or comparable to those of the best available existing models.

Falling Film Evaporation of Water on Horizontal Configured Tube Bundles

2010 ◽  
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.

Microscopic mechanisms of heat transfer in horizontal-tube falling film evaporation

Desalination ◽  
2016 ◽  
Vol 394 ◽  
pp. 64-71 ◽  
Author(s):  
Luopeng Yang ◽  
Yang Liu ◽  
Yan Yang ◽  
Shengqiang Shen
Keyword(s):  
Heat Transfer ◽  
Horizontal Tube ◽  
Falling Film ◽  
Film Evaporation ◽  
Falling Film Evaporation

Experimental Study of Heat Transfer Characteristics for Horizontal-Tube Falling Film Evaporation

2012 ◽  
Author(s):  
Xingsen Mu ◽  
Yong Yang ◽  
Shengqiang Shen ◽  
Gangtao Liang ◽  
Luyuan Gong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fresh Water ◽  
Horizontal Tube ◽  
Falling Film ◽  
Heat Transfer Characteristics ◽  
Film Evaporation ◽  
Transfer Characteristics ◽  
Falling Film Evaporation

The horizontal-tube falling film evaporation is a widely adopted technique in multiple-effect distillation (MED) desalination plant due to the higher heat transfer coefficient under quite small temperature differences. In the present study, an experimental platform for horizontal-tube falling film evaporation was set up to measure its heat transfer characteristics. Results indicate that heat transfer coefficient (h) for both fresh water and seawater are almost independent with heat flux. The h increases firstly and then decreases with growth of Re. Along the tube circumference, the h increases after decreasing. In addition, the distribution of h for fresh water and seawater at the different evaporation temperatures and Reynolds number (Re) are also provided.

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