scholarly journals Discussion: “Heat Transfer in an LTV Falling Film Evaporator: A Theoretical and Experimental Analysis” (Kroll, J. E., and McCutchan, J. W., 1968, ASME J. Heat Transfer, 90, pp. 201–210)

1968 ◽  
Vol 90 (2) ◽  
pp. 210-210
Author(s):  
Richard L. Hummel
Keyword(s):  
Heat Transfer ◽  
Experimental Analysis ◽  
Falling Film ◽  
Film Evaporator

Heat Transfer in an LTV Falling Film Evaporator: A Theoretical and Experimental Analysis

1968 ◽  
Vol 90 (2) ◽  
pp. 201-210 ◽  
Author(s):  
J. E. Kroll ◽  
J. W. McCutchan
Keyword(s):  
Heat Transfer ◽  
Mathematical Models ◽  
Flow Rate ◽  
Experimental Analysis ◽  
Experimental Results ◽  
Falling Film ◽  
Film Evaporator ◽  
Good Agreement

Two slightly differing mathematical models were developed to describe the heat transfer in the long tube vertical falling film process. The process was investigated experimentally with a 3/4 in. dia tube for various lengths up to 13 ft, for flow rate Reynold’s numbers from 1000 to 13000, for temperature differences of the order of 20 deg F, and for vacuum conditions down to 160 deg F. A comparison of theoretical and experimental results was made and was found to be in good agreement; that is, within 10 percent.

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.

Evaporation of Pure Liquids at High Prandtl Numbers in a Scale-Up Capable Falling Film Evaporator

2010 ◽  
Author(s):  
Stefanie Arndt ◽  
Stephan Scholl
Keyword(s):  
Heat Transfer ◽  
Scale Up ◽  
Reynolds Numbers ◽  
Temperature Sensitive ◽  
Turbulent Regime ◽  
Falling Film ◽  
Film Evaporator ◽  
Laminar And Turbulent Flow ◽  
Falling Film Evaporation ◽  
Prandtl Numbers

In industrial application heat transfer to temperature sensitive products in falling film evaporation is often linked to the evaporation at elevated viscosities. In the present study a scale-up capable falling film evaporator has been used to investigate the heat transfer to liquids with Prandtl numbers up to 150. The focus was on heated falling films during surface evaporation. Film-Reynolds numbers were varied from 48 to 10,000. As pure liquids water and cyclohexanol were used. In the results a distinct transition zone between laminar and turbulent flow can be observed for elevated Prandtl numbers. The comparison to literature models shows that more parameters have to be taken into account to properly predict the heat transfer in falling film evaporators for different equipment and fluids. The optical monitoring of the film on the inside of the evaporation tube through an endoscope showed that the fully turbulent regime could not been reached for high viscosities.

Research on Energy-Saving Technology for Salt Solution Heat Pump Evaporators

2013 ◽  
Vol 331 ◽  
pp. 216-221
Author(s):  
Tian Lan Yu ◽  
Tian Xiang Yu ◽  
De Qi Peng ◽  
Li Chen ◽  
Xiu Yan Feng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Saving ◽  
Heat Pump ◽  
Salt Solution ◽  
Pump Energy ◽  
Stable Operation ◽  
Falling Film ◽  
Film Evaporator ◽  
Evaporation Energy ◽  
Theoretical Analyses

Aiming at increasing the energy-saving efficiency of salt solution evaporation, the effect of several factors on heat pump energy-saving efficiency is studied through theoretical analyses and calculation. The factors include boiling point elevation caused by solution static pressure, superheat loss of surface evaporation, temperature difference loss caused by fouling. The conclusions are that falling-film evaporator helps improve heat pump evaporation energy-saving the most and forms the fluctuating flow of the falling film which can be used to remove fouling automatically. The Φ38mm×2mm single-tube dynamics experiment results show that the flow can produce stable 3D vibration of the cleaning spiral when the nominal flow velocity is more than 0.25m/s. The axial reciprocating motion distance is longer than one spiral pitch and reciprocating periodicity is 3-6 seconds. The sodium carbonate solution fouling removal experiment results show that the salt fouling decreases the overall heat transfer coefficient by 30% in one hour when there is no the 3D vibrating spiral-insert; and the insert can enhance heat transfer by 59% comparing to that during stable operation without this technology. Key Words: Falling-film Evaporator, Heat Pump Evaporate, Energy saving, Automatic cleaning, Heat transfer

Theoretical and Experimental Study on the Falling-Film Evaporator Applied to Mechanical Vapor Compression

2013 ◽  
Vol 753-755 ◽  
pp. 2667-2673 ◽  
Author(s):  
Wei Ke Pang ◽  
Lu Wei Yang ◽  
Zhen Tao Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
High Efficiency ◽  
Film Flow ◽  
Falling Film ◽  
Vapor Compression ◽  
Pump System ◽  
Heat Pump System ◽  
Film Evaporator ◽  
Heat Transfer Efficiency

Based on a heat pump system of mechanical vapor recompression (MVR) designed and manufactured independently, the heat transfer performance of falling-film evaporator was measured by a combination way of theory analysis and experiment proving as the heat pump operated in practice. After the result of theoretical calculation is worked out, the start thickness and entrance velocity of the liquid film are established by adjusting the flux of raw solution. The result shows there is an optimization that the film thickness at the bottom of the tubes amounts to that of boundary layer of velocity. Additionally, it is a process of falling-film flow with heat and mass transfer between the start and end of falling-film. The last thickness of the falling film is about 0.21~0.44mm. The thickness of falling film when the falling-film flowed and heat exchange was over is compared with each other, and the effect of heat resistance on heat transfer is discussed also. It is showed that an optimal thickness is formed during the process of falling-film flow and evaporation, and disadvantages come up when it is not formed. The falling-film evaporator propelled by the MVR heat pump with low compression ratio carries through a process of strong and high-efficiency heat transfer with phase transition. It is because the states of produced vapor both before compressed and after compressed are saturated. Its heat-transfer coefficient may be as high as 1990 W/ (m2·K). The start and end thickness of falling film become great while the evaporation pressure goes up. It leads to the drop of the heat-transfer efficiency, so there is an optimization to the system in all probability.

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