Study on Liquid Film Thickness of Accelerated Slug Flow in Micro Tubes

Liquid film thickness data in slug flow in a 320 μm diameter capillary tube have been obtained and are compared with existing data and correlations. Solutions of glycerol in water at varying concentrations between 50 and 70% were injected into the capillary tube along with air, at ambient temperature. The thickness of the liquid film was measured using a laser confocal displacement sensor. Gas slug velocity data were obtained from high speed video images recorded at 40,000 frames per second. As liquid viscosity and hence capillary number was reduced, the film thickness around the gas slugs in the capillary tube decreased as expected. The liquid film thickness data were slightly underpredicted by existing correlations.

Download Full-text

Liquid Film Thickness in Micro Channel Slug Flow

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

10.1115/icnmm2009-82150 ◽

2009 ◽

Cited By ~ 1

Author(s):

Naoki Shikazono ◽

Youngbae Han

Keyword(s):

Boundary Layer ◽

Film Thickness ◽

Liquid Film ◽

Capillary Number ◽

Slug Flow ◽

Thin Liquid Film ◽

Inertial Force ◽

Liquid Film Thickness ◽

Micro Channel ◽

Viscous Boundary Layer

Slug flow is the representative flow regime of two-phase flow in micro channels. It is well known that the thin liquid film formed around the confined vapor bubble plays an important role in micro channel heat transfer. In the present study, experiments are carried out to clarify the effects of parameters that affect the formation of the thin liquid film in micro channel slug flow. Laser focus displacement meter is used to measure the thickness of the thin liquid film. Air, ethanol, water and FC-40 are used as working fluids. Circular tubes with five different diameters, D = 0.3, 0.5, 0.7, 1.0, 1.3 mm, and square channels with two different sizes, 0.3 × 0.3 and 0.5 × 0.5 mm, are used. It is confirmed that the liquid film thickness is determined only by capillary number at small capillary numbers. However, the effect of inertial force and flow acceleration cannot be neglected as capillary number increases. The effect of cross sectional shape is also investigated. Experimental correlation for the adiabatic liquid film thickness in circular tubes based on capillary number, Reynolds number and Weber number is proposed. When viscous boundary layer is thin, liquid film thickness is limited by the viscous boundary layer thickness. Thus, in order to develop precise flow boiling models in micro tubes, it is important to consider the effects of inertial force and boundary layer thickness on the liquid film thickness.

Download Full-text

Experimental Investigation of Annular Flow Behaviour in Horizontal Pipe

International Journal of Integrated Engineering ◽

10.30880/ijie.2021.13.06.014 ◽

2021 ◽

Vol 13 (6) ◽

Author(s):

Osokogwu Osokogwu ◽

◽

Uche Uche ◽

Keyword(s):

Film Thickness ◽

Liquid Film ◽

Slug Flow ◽

High Speed ◽

Annular Flow ◽

Flow Behavior ◽

Liquid Film Thickness ◽

Experimental Investigations ◽

Internal Diameter ◽

Horizontal Pipe

The experimental investigations of annular flow were conducted in horizontal pipe using water/air in a 0.0504m internal diameter pipe loop with a total length of 28.68m. To understand annular flow behaviors, conductivity ring sensors, conductance probe sensors and Olympia high speed digital camera were used. In all the experiments, emphasis were on annular flow behavior, phase distribution and liquid film thickness. Liquid film thickness was observed to be thicker mostly when the superficial gas velocities were within 8.2699 m/s to 12.0675 m/s. Above the aforementioned superficial gas velocities, the flow became uniformly distributed on the walls of the internal pipe diameter hence reducing the thicker liquid film at the bottom with gas core at the center of the pipe. More so, annular-slug flow was discovered in the investigation. At superficial liquid velocity of 0.0505 m/s-0.1355 m/s on superficial gas velocities of 8.2699 m/s – 12.0675 m/s, annular-slug flow was prominent. Also discovered was at superficial liquid velocities of 0.0903 m/s - 0.1355 m/s with respect to superficial gas velocities of 13.1692 m/s – 23.4575 m/s, the pipe walls are fully covered with liquid film at very high speed at the entire walls (upper walls and bottom). Also discovered in this experiment is the wavy flow of the upper walls. The liquid film thickness that flows at the upper pipe walls, creeps in a wavy flow. Therefore, the entire flow behavior in an annular flow could be grouped into; wavy-flow at the upper walls, annular-slug flow and thicker liquid film at the bottom with gas core at the center.

Download Full-text