Two-phase flow patterns in adiabatic refrigerant flow through capillary tubes

A gas-liquid two-phase flow in a capillary tube or a narrow passage is encountered in many applications, for example, the flow of coolant in evaporators of many kinds of heat exchangers. Sufficlent information on fundamental parameters, such as void fraction and pressure drop, however, are not available in designing such devices. In the present investigation, we made a detailed observation of the flow pattern of an air-water two-phase flow in a horizontal capillary tube with an inner diameter of 1.0mm to 4.9mm, and attempted to correlate and explain the behavior of the pressure drop changing with the flow rates of both phases by introducing a physical model.

The effects of the parameters of a refrigeration system working with R600a on the non-equilibrium subcooled two-phase flow of the refrigerant

Quality measurement of refrigerant two-phase flow in refrigeration cycles

Effect of liquid-vapor two-phase flow maldistribution on the thermal performance of brazed plate heat exchangers

Experimental and numerical investigation on the flow of mixed refrigerants through capillary tubes at cryogenic temperatures

Convolutional neural network for flow boiling patterns classification

The behaviour of two-phase gas-liquid flows in a stopper-rod controlled submerged entry nozzle (SEN) is investigated in water model experiments. The observed two-phase flow patterns can be classified into either bubble coring or bubbly slug. The scaling of the two-phase flows by means of similarity parameters is discussed. In the experiments, it is found that the liquid flow rates depend strongly on the two-phase flow patterns. Additionally, the influence of swirl on the flow patterns is investigated in detail. It is shown that swirl has a marked impact on the transition from bubble coring to bubbly slug. Finally, an estimation of the two-phase argon-steel flow patterns in industrialscale SEN flows is given.

Quantitative void fraction measurement method by neutron radiography and applications to two-phase flow researches

This paper presents correlations for sizing adiabatic capillary tubes which serves as an expansion device in split-type air-conditioner with LPG, novel hydrocarbon (HC) mixtures of butane (HC600) and propane (HC290) as refrigerant. A homogenous two-phase flow model developed by the authors and also experimental investigation of the Liquified Petroluem Gas (LPG) refrigerant flow in adiabatic capillary tubes were used in this study. The theoretical model was used to assess various percentage compositions of these HC mixtures and validated with the experimental data. For each HC refrigerant mixture, correlations for sizing adiabatic capillary tube which contains the relevant factors, viz. capillary tube inner diameter, inlet pressure, refrigerant mass flow rate, capillary tube surface roughness and capillary tube inlet subcooling was developed. The proposed correlations were compared with the authors measured data and found to be in good agreement. Further validation was made by comparing the mass flow rates predictions of the correlations with experimental data of previous studies and found that these correlations are consistent. The correlations can be used in small vapour compression refrigeration systems working with the HC refrigerant mixtures for practical design and optimization.

A two-phase flow is the simplest form of multi-phase flow. Two-phase flow has basic parameters, including flow behavior, flow pattern, void fraction, pressure gradient, or pressure drop. The development and application of fluid flow in small channels (mini and micro) are in the Micro Electromechanical System (MEMS). In general, the application of two-phase flow can be found in various applications in the industrial world, such as boilers, cores, and steam generators in nuclear reactors, petroleum transportation, electronic cooling, and different other types of chemical reactors. One of the most common challenges is void fractions and flow patterns in horizontal and vertical pipelines. The purpose of this study was to find out the significant difference in the characteristic value of fundamental parameters, primarily void fractions and flow patterns that occur in capillary pipes with a slope of 15o to horizontal. The fraction value and shape of this flow pattern are essential because it determines the pressure drop value, which means determining the level of danger that can occur if the pressure drop value reaches the extreme value. The fluid used a mixture of air-water and glycerin with 0, 10, 20, and 30% concentrations. To determine the void fraction is used digital image processing method with MATLAB R2014a application. A 1200 fps high-speed camera and 640 x 480-pixel resolution are used for video shooting. The experiment was conducted at superficial gas (JG) velocities of 0.025 - 66.3 m/s and superficial fluid velocities (JG) intervals of 0.033 – 4.935 m/s. The experiment results showed a significant difference between the void fraction value for the bubbly flow pattern and the churn flow pattern, which has not been widely discussed in previous studies. The analysis concluded that the higher the velocity of superficial gases, the void fraction value increases. This increase in the void fraction is why there is a significant change in flow patterns from bubble flow patterns to churn. In addition, it was also found that the increased viscosity of the fluid significantly affected changes in flow patterns, incredibly bubbly and plug, but its velocity decreased. It is also the result that the higher homogeneous void fraction (β) value affects the increase in the length of bubbly flow patterns and plugs.

A numerical and experimental study is reported for two-phase flow and heat transfer in a horizontal porous formation with water through flow and partial heating from below. Based on a newly developed two-phase mixture model, numerical results of the temperature distribution, liquid saturation, liquid and vapor phase velocity fields are presented for three representative cases with varying inlet velocities. It is found that the resulting two-phase structure and flow patterns are strongly dependent upon the water inlet velocity and the bottom heat flux. The former parameter measures the flow along the horizontal direction, while the latter creates a relative motion between the phases in the vertical direction. Experiments are also performed to measure temperature distributions and to visualize the two-phase flow patterns. Qualitative agreement between experiments and numerical predictions is achieved. Overall, this combined experimental and numerical study has provided new insight into conjugate single- and two-phase flow and heat transfer in porous media, although future research is required if accurate modeling of these complex problems is to be accomplished.

Flow pattern transition for vertical downward two-phase flow in capillary tubes. Inlet mixing effects

Numerical simulation for heat transfer and velocity field characteristics of two-phase flow systems in axially rotating horizontal cans

A physicomathematical model of a two-phase liquid flow in a discrete fracture network—taking into account a nonuniform fracture aperture, flow exchange between fractures, capillary and gravitational forces—is presented. Capillary forces are described by the Young-Laplace model that takes into account the rock wetting angle and surface tension. The influence of the structure of the conducting channels in a fracture, capillary and gravitational forces, and the pressure gradient, as well as the water-and-oil viscosity ratio on the flow dynamics and the oil recovery factor, is explored. It is shown that capillary forces and the structure of channels in a fracture can play a decisive role in the process of oil displacement by water.

Supercritical CO2 behaviour during water displacement in a sandstone core sample