Improved Heat Transfer Performance of Falling Film Evaporator for Desalination Industry by Balanced Liquid Distribution

2020 ◽  
Vol 59 (46) ◽  
pp. 20492-20503
Author(s):  
Chuanpeng Cao ◽  
Lixin Xie ◽  
Shichang Xu ◽  
Qian Liu ◽  
Yawei Du
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Falling Film ◽  
Liquid Distribution ◽  
Film Evaporator

Studying the Effect of Porosity of Porous Layer Coating on the Performance of the Horizontal Tubular Falling Film Evaporator

2021 ◽  
Author(s):  
Alaa Adel Ibrahim ◽  
Hassan Elgamal ◽  
Ahmed M. Nagib Elmekawy
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Numerical Simulations ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Falling Film ◽  
Film Evaporator ◽  
Porosity Ratio ◽  
Layer Coating

Abstract Through the recent decades, many studies have focused on finding efficient methods to enhance the heat transfer performance in heat exchangers. Therefore, using porous media attracted many researchers, as it is such a simple, efficient, and low-cost technique in enlarging the surface contact area of heat transfer through the fluid pass. Nevertheless, there is little work associated with using porous media to enhance the thermal performance of falling film evaporators. The present study seeks to discuss numerically the liquid flow behaviour over falling film evaporator tubes in the case of bare tubes and tubes with porous layer coating. The two-dimensional multi-phase numerical simulations are also carried out in order to investigate the effect of the porosity ratio of the porous medium added to the tubes in the heat transfer performance. Furthermore, deducing the way to select a decent porosity ratio to be used to get the best thermal performance is demonstrated through the study. Time-averaged results gained from the numerical simulations have been compared to those of bare-tube falling film evaporator to observe much higher heat transfer performance represented in the average surface Nusselt number (Nu) which increased by 3 times.

Combined Heat and Mass Transfer Under Different Inlet Subcooling Modes During NH3-H2O Falling Film Absorption Process

2001 ◽  
Vol 123 (3) ◽  
pp. 242-249 ◽  
Author(s):  
Y. T. Kang ◽  
Y. Fujita ◽  
T. Kashiwagi
Keyword(s):  
Heat Transfer ◽  
Water Absorption ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Falling Film ◽  
Absorption Process ◽  
Concentration Difference ◽  
Ammonia Water ◽  
Absorption Performance ◽  
Falling Film Absorption

Experiments were conducted for ammonia-water falling film absorption in a plate heat exchanger with offset strip fins. The objectives of this paper were to analyze combined heat and mass transfer during the ammonia-water absorption process under different inlet subcooling modes, and to obtain heat transfer coefficients (Nusselt number). This paper examined the effects of the inlet subcooling modes, the inlet concentration difference, liquid Reynolds number, and vapor Reynolds number on the heat transfer performance. Inlet liquid concentrations were set at 0, 5, 10, and 15 percent in mass of ammonia, while inlet vapor concentration ranged from 64.7 to 83.6 percent. Experiments were conducted in three ways according to the inlet subcooling conditions, i.e., Case A Tv>Tl, Case B Tv∼Tl, and Case C Tv<Tl. In Case A, there was a rectification process at the top of the test section by the inlet subcooling effect. Water desorption was confirmed in the experiments, which resulted in a lower absorption performance. The heat transfer coefficient increased as the inlet subcooling increased in all cases. The effect of inlet subcooling on heat transfer performance was more significant in Case A than in Cases B and C. The inlet subcooling had more significant effect on the heat transfer performance than the inlet concentration difference. Nusselt number increased as liquid and vapor Reynolds numbers increased. The vapor velocity should be maximized to increase absorption performance in cocurrent ammonia-water absorption process. The parametric analysis provides fundamental understandings of the ammonia-water absorption process, and thus gives a guideline for heat exchanger compactness in ammonia-water absorption systems.

Experimental Investigation of Falling Film Evaporation on Horizontal Tubes at Low-Pressure

2011 ◽  
Vol 236-238 ◽  
pp. 1572-1575 ◽  
Author(s):  
Hong Liu ◽  
Hu Gen Ma ◽  
Chang Sheng Li
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Falling Film ◽  
Film Evaporation ◽  
Horizontal Tubes ◽  
Falling Film Evaporation ◽  
The Impact

Experimental investigation of falling film evaporation on horizontal tubes was carried out in this paper. Tube surface, spray flow rate and coolant flow rate were the factors considered in the experiment. The impact on falling film evaporation performance was obtained as expected. Experimental results are obtained that the heat transfer performances of low finned tubes are better than that of smooth tubes. The increasing of flow rate enhances heat transfer performance of falling film evaporation at first, while the flow rate gets a certain value, it will hinder the improvement of heat transfer performance. It was also found that there is almost no effects on heat transfer coefficient when the flow rate of coolant changes.

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