Effects of the plate material characteristics and its inclination angle on falling film breakup

Effects of Inclination Angle on Falling Film Evaporation Using R-134a

Heat Transfer: Volume 4 ◽

10.1115/ht2005-72149 ◽

2005 ◽

Author(s):

Liang-Han Chien ◽

Hung-Ta Lin

Keyword(s):

Heat Transfer ◽

Inclination Angle ◽

Falling Film ◽

Film Evaporation ◽

Evaporation Heat ◽

Finned Surface ◽

Falling Film Evaporation ◽

Plain Surface ◽

Evaporation Heat Transfer ◽

R 134A

This manuscript discusses the effect of inclination angle and surface geometries on the falling film evaporation performance. Falling film evaporation experiments were conducted on a smooth plate and finned plates using refrigerant R-134a at 18 °C system temperature. The plate was inclined with angles between 10° and 40°, and the heat fluxes are between 36 and 73.5kW/m2. The local heat transfer coefficients are measured, and the falling film flow distribution is observed through a sight glass. The test results showed that the falling film evaporation heat transfer coefficient increases as the inclination angle increases or the heat flux increases. The finned surface yields better falling film evaporation heat transfer performance than the smooth surface. The ratio of the heat transfer coefficient of the finned surface versus the plain surface is between 2.5 and 12.4 folds. This ratio increases as the inclination angle increases. The visualization observation showed that bubble nucleation is more pronounced on the finned surface than the plain surface. The effect of boiling on falling film evaporation is discussed.

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Long-Wave and Integral Boundary Layer Analysis of Falling Film Flow on Walls With Three-Dimensional Periodic Structures

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82115 ◽

2009 ◽

Author(s):

Tatiana Gambaryan-Roisman ◽

Hongyi Yu ◽

Karsten Lo¨ffler ◽

Peter Stephan

Keyword(s):

Boundary Layer ◽

Reynolds Number ◽

Inclination Angle ◽

Film Flow ◽

Three Dimensional ◽

Falling Film ◽

Integral Boundary ◽

Long Wave ◽

Surface Patterns ◽

Periodic Microstructures

Falling films exhibit very complex wavy patterns, which depend on the properties of the liquid, the Reynolds number, the wall inclination angle, and the distance from the film inlet. The film hydrodynamics and the surface patterns have a high impact on heat and mass transfer. Our aim is to control and enhance heat and mass transport by using walls with specific micro topographies that influence the falling film flow, stability and wavy pattern. In the present work long-wave theory and integral boundary layer (IBL) approximation are used for modelling the falling film flow on walls with three-dimensional periodic microstructures. The wall topography is periodic both in the main flow direction and in the transverse direction. Examples of such microstructures are longitudinal grooves with sinusoidal path (or meandering grooves) and herringbone structures. The effects of the Reynolds number, the wall inclination angle and the longitudinal and transverse periods of the structure on the shape of liquid-gas interface are investigated. It is shown that, as opposed to straight grooves in longitudinal direction, grooves with meandering path may lead to significant interface deformations.

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Modeling and Optimizing of Producing Recycled PET from Fabrics Waste via Falling Film-Rotating Disk Combined Reactor

International Journal of Polymer Science ◽

10.1155/2017/1062493 ◽

2017 ◽

Vol 2017 ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Dan Qin ◽

Chaosheng Wang ◽

Huaping Wang ◽

Ye Chen ◽

Peng Ji ◽

...

Keyword(s):

Liquid Phase ◽

Product Quality ◽

Intrinsic Viscosity ◽

Rotating Disk ◽

Plant Production ◽

Utilization Rate ◽

Falling Film ◽

Recycled Pet ◽

Specific Product ◽

Material Characteristics

Recycling and reusing of poly (ethylene terephthalate) (PET) fabrics waste are essential for reducing serious waste of resources and environmental pollution caused by low utilization rate. The liquid-phase polymerization method has advantages of short process flow, low energy consumption, and low production cost. However, unlike prepolymer, the material characteristics of PET fabrics waste (complex composition, high intrinsic viscosity, and large quality fluctuations) make its recycling a technique challenge. In this study, the falling film-rotating disk combined reactor is proposed, and the continuous liquid-phase polymerization is modeled by optimizing and correcting existing models for the final stage of PET polymerization to improve the product quality in plant production. Through modeling and simulation, the weight analysis of indexes closely related to the product quality (intrinsic viscosity, carboxyl end group concentration, and diethylene glycol content) was investigated to optimize the production process in order to obtain the desired polymer properties and meet specific product material characteristics. The model could be applied to other PET wastes (e.g., bottles and films) and extended to investigate different aspects of the recycling process.

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