Falling Water Film Evaporation on Horizontal Finned Tube Arrays at Low Pressure

2011 ◽  
Author(s):  
Xiao-Yu Wu ◽  
Wei Li ◽  
Zhong Luo
Keyword(s):  
Heat Transfer ◽  
Experimental Studies ◽  
Water Film ◽  
Finned Tube ◽  
Heat Fluxes ◽  
Falling Film ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Film Evaporation ◽  
Falling Film Evaporation

Experimental studies have been done on falling film evaporation of water on four types of finned tubes arrays at the pressure of 1000 Pa. The Reynolds numbers are in the laminar range of about 10 to 110. Results show that the finned tubes that can distribute liquid longitudinally have the best performances in the partial dryout regime, and those with high fins could enhance heat transfer most in the fully wet regime. High heat fluxes will make more liquid evaporate, but also generate more dry patches on the tubes. Additionally, the inner enhancement of the tubes will also improve the overall heat transfer coefficients. And four heat transfer enhancement methods of falling film evaporation are summarized in the paper.

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.

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.

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.

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.

Prediction of Heat Transfer Coefficients in Gas Flow Normal to Finned and Smooth Tube Banks

1981 ◽  
Vol 103 (4) ◽  
pp. 705-714 ◽  
Author(s):  
J. C. Biery
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Finned Tube ◽  
Smooth Tube ◽  
Transfer Coefficients ◽  
Tube Bank ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Tube Banks

A new method is presented to predict heat transfer coefficients for gas flow normal to smooth and finned tube tanks with triangular pitch. A transformation from the actual tube bank to an equivalent equilateral triangular pitch infinite smooth tube bank (ETP-I-STB) is made. A function of Ch(Ch = NSTNPR2/3NRe0.4) versus (Xt D0)Δ, ratio of transverse pitch to tube diameter for the ETP-I-STB, was developed. The Ch for the equivalent ETP-I-STP then applies to the actual tube bank. The method works with circular finned tubes, smooth tubes, continuous finned tubes, and segmented finned tubes with any triangular pitch. Also, fair predictions were made for in-line tubes with high Reynolds numbers.

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.

Heat Transfer and Fouling Performance During Falling Film Evaporation in Vertical Porous Tubes

2020 ◽  
Author(s):  
Lei Wang ◽  
Weiyu Tang ◽  
Limin Zhao ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Falling Film ◽  
Film Evaporation ◽  
Falling Film Evaporation ◽  
The Heat Transfer Coefficient

Abstract An experimental investigation was conducted on falling film evaporation along two porous tubes, which were sintered by stainless-steel powder with a diameter of 0.45 and 1 um, respectively. The test section is a 2 m long sintered tube with an outer diameter of 25 mm and a wall thickness of 2 mm. During the experiment, the pressure inside the tube was maintained at 1 atm, the inlet temperature was 373 K, and mass flux ranged from 0.51 to 1.36 kg/ (m s). Conditions of the steam outside the pipe, which was the heat source, were fixed, while the fouling tests were carried out at a constant mass flow of 0.74 kg/ (m s) using high-concentration brine as work fluid. The overall heat transfer coefficient under different working conditions was tested and compared with the stainless steel smooth tube of the same dimensions. The heat transfer coefficient of the two porous stainless tubes are about 35% and 20% lower than that of the smooth one, showing an inferior effect because the steam in the pores of the pipe wall during the infiltration process will reduce the heat conductivity. The heat transfer coefficient of the smooth tube deteriorated severely due to the deposition of calcium carbonate, which had little effect on the sintered tubes. Besides, the fouling weight of porous tubes is 2.01 g and 0 g compared with 5.52 g of the smooth tube.

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