Experimental Characterization of Oil-Refrigerant Two-Phase Flow

Mapping Intimacies ◽

10.1115/imece2000-1302 ◽

2000 ◽

Author(s):

V. T. Lacerda ◽

A. T. Prata ◽

F. Fagotti

Keyword(s):

Flow Visualization ◽

Two Phase Flow ◽

Working Fluid ◽

Phase Flow ◽

Oil Viscosity ◽

Two Phase ◽

Mixture Flow ◽

Horizontal Tubes ◽

Constant Diameter ◽

Oil Flow

Abstract Several phenomena occurring inside refrigerating systems depend on the interaction between the refrigeration oil and the refrigerant working fluid. Regarding the refrigeration cycle, good miscibility of oil and refrigerant assure easy return of circulating oil to the compressor through the reduction of the oil viscosity. Inside the compressor the lubricant is mainly used for leakage sealing, cooling of hot elements and lubrication of sliding parts. In the compressor bearing systems the presence of refrigerant dissolved in the oil greatly influences the performance and reliability of the compressor due to the outgassing experienced by sudden changes in temperature and pressure resulting in a two-phase mixture with density and viscosity strongly affecting the lubricant characteristics. A general understanding of the oil-refrigerant mixture flow is crucial in developing lubrication models to be used in analysis and simulation of fluid mechanics problems inside the compressor. In the present investigation the refrigeration oil flow with refrigerant outgassing is explored experimentally. A mixture of oil saturated with refrigerant is forced to flow in two straight horizontal tubes of constant diameter. One tube is used for flow visualization and the other is instrumented for pressure and temperature measurements. At the tubes inlet liquid state prevails and as flow proceeds the pressure drop reduces the gas solubility in the oil and outgassing occurs. Initially small bubbles are observed and eventually the bubble population reaches a stage where foaming flow is observed. The flow visualization allowed identification of the two-phase flow regimes experienced by the mixture. Pressure and temperature distributions are measured along the flow and from that mixture quality and void fraction were estimated.

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Numerical Investigation of Two-Phase Flow in 45 Degrees “Y” Junctions

Volume 7B: Fluids Engineering Systems and Technologies ◽

10.1115/imece2015-50631 ◽

2015 ◽

Author(s):

Carlos Chacon ◽

Carlos Moreno ◽

Miguel Arbej ◽

Miguel Asuaje

Keyword(s):

Oil And Gas ◽

Two Phase Flow ◽

Petroleum Industry ◽

Continuous Phase ◽

Working Fluid ◽

Phase Flow ◽

Two Phase ◽

Flow Energy ◽

Oil Flow ◽

Oil Gas

Frequently, Two-phase flow occurs in petroleum industry. It takes place on production and transportation of oil and natural gas. Initially, the most common patterns for vertical flow are Bubble, Slug, Churn and Annular Flow. Then, for horizontal flow, the most common patterns are Stratified Smooth, Stratified Wavy, Elongated Bubble, Slug, Annular, Wavy Annular and Dispersed Bubble Flow. It is also known that after separation, each fluid is carried through pipes, so oil is moved long distances. However, as it is known, the oil energy diminishes on the way. For that reason, it is needed a pumping station for keeping the oil flow energy high for proper movement. Additionally, that fluid is transported through a network, so fittings are present, like elbows, “T” and “Y” junctions, and others. As known, on a piping network, the losses can be classified in two groups: large and localized. The former consists on losses due to wall roughness-fluid interaction. The latter is related with fittings. This study is focused on 45° “Y” junctions. The main purpose of this study is to simulate the fluid flow on a 45° “Y” junction, using a 0.1143 m diameter 2 m length pipe, in which a 0.0603 m diameter 1 m length pipe confluences, using oil-gas as the working fluid, considering Dispersed Bubble Pattern. It can be attributed a “K” flow loss coefficient for each path, from each entry to the exit of the junction. For the Two-Phase Flow, it was supposed a horizontal Dispersed Bubble Pattern, which takes place at very high liquid flow rates. So the liquid phase is the continuous phase, in which the gas phase is dispersed as discrete bubbles. Particularly three API Grades were considered for the oil, corresponding to three main types of continuous phase. For the numerical model, it was generated several non-structured grids for validation, using water as a fluid. Then the simulations were carried out, using non-homogenous model, with oil and gas, changing the gas void fraction, and the superficial velocities for gas and liquid. A commercial package was used for numerical calculations. It was encountered that changing the value of the referred variables, in some cases the exit pressure of the “Y” junction diminishes. For validation of the results, a literature model was used for comparing both “K” loss coefficients: numerically and from the bibliography. It is important to highlight that these results, permit to analyze a way of diminishing the fluid energy losses in a Two-Phase oil-gas piping network, particularly in 45° “Y” junctions which represents economically saving.

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Developments of a Flow Visualization Borescope and a Two-Phase Flow Probe for Aeroengine Transmission Gears

Volume 1: Aircraft Engine; Fans and Blowers; Marine ◽

10.1115/gt2018-75083 ◽

2018 ◽

Author(s):

Hidenori Arisawa ◽

Yuji Shinoda ◽

Yoshiyuki Noguchi ◽

Tatsuhiko Goi ◽

Takahiko Banno ◽

...

Keyword(s):

Flow Visualization ◽

Flow Velocity ◽

Two Phase Flow ◽

High Speed Photography ◽

Phase Flow ◽

Flow Probe ◽

Two Phase ◽

Peripheral Speed ◽

Diameter Pipe ◽

Oil Flow

In order to reduce oil dynamic power loss in aeroengine gearboxes, visualizations and measurements of the oil-flow are effective. In the research presented in this paper, we developed a flow visualization borescope which can qualitatively visualize oil flow and a two-phase flow probe which can quantitatively measure oil/air ratio and the flow velocity. The flow visualization borescope consists of a 16mm diameter pipe in which an air purge passage for removing oil mist and a borescope are integrated with an illumination laser light and optical lenses, enabling clear high-speed photography. The two-phase probe consists of a 5mm diameter pipe with a 1mm diameter measurement hole and has a pressure adjustment pipe inside the pipe. For a demonstration, a shrouded spur gear with 100 m/s peripheral speed and 20 liters/min oil supply was used. Flow visualization at 30000 frame/sec imaging shows that oil outflow from the shroud opening spreads turbulently over the whole width of the opening. Oil/air ratio and flow velocity measurement by the two-phase flow probe show that there was thin oil-rich layer on the shroud wall and the flow speed was slow compared with the gear peripheral speed. The measurement equipment we developed was easily installed to the gearbox and therefore it is expected to apply to real aeroengine gearboxes.

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Modeling of Two-Phase Flow through a Rotating Tube with Twin Exit Branches

International Journal of Rotating Machinery ◽

10.1155/s1023621x00000154 ◽

2000 ◽

Vol 6 (3) ◽

pp. 159-166 ◽

Cited By ~ 1

Author(s):

Sun-Wen Cheng ◽

Wen-Jei Yang

Keyword(s):

Single Phase ◽

Two Phase Flow ◽

Automatic Transmission ◽

Flow Regimes ◽

Working Fluid ◽

Drilling Process ◽

Phase Flow ◽

Two Phase ◽

Flow Rates ◽

Oil Flow

A numerical model is proposed to determine the dynamic behavior of single-phase and twophase, two-component flows through a horizontal rotating tube with identical twin exit branches. The working fluid, oil, enters the tube through a radial duct attached at one end and exits into open air through the twin radial branches, one located at midway and the other at the end of the tube. The branch-to-tube diameter ratio, rotational speed, and total oil flow rate are varied. It is experimentally revealed in previous study that the air cavitation occurs at lower speeds, leading to a two-phase flow with the air-oil ratio (void fraction) varying with the rotating speed. A unique characteristic in two-phase flow, i.e., hysteresis, is found to exist in both oil flow rates and inlet pressure. In theoretical modeling, the governing flow equations are incorporated by empirical equations for hydraulic head losses. The predicted and measured exit oil flow rates are compared with good agreement in both the single-phase and annular flow regimes. Only qualitative agreement is achieved in the bubbly and bubbly-slug flow regimes. The model can be applied to improve the design and thus enhance the performance of automatic transmission lines, and the cooling efficiency of rotating machines and petroleum drilling process.

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