No abstract

In this work, the slug flow regime in an air-water horizontal pipe flow has been simulated using the CFD technique. The variables identified to characterise the slug regime are the slug length and slug initiation. Additionally, the pressure drop and the pressure distribution within the simulated pipe segment have been predicted. The volume of fluid method was employed assuming unsteady, immiscible airwater flow, constant fluid properties and coaxial flow. The model was developed in the STAR-CCM+ environment, and the grid was designed in the three dimensional domain using directed mesh. A grid independency study was carried out through the monitoring of the water velocity at the outlet section. 104,000 hexahedral cells for the entire geometry were decided on as the best combination of computing time and accuracy. The simulated pipe segment was 8 m long and had a 0.074 m internal diameter. Three cases of air-water volume fractions have been investigated, where the water flow rate was pre-set at 0.0028 m 3 /s, and the air flow rate was varied at three dissimilar values of 0.0105, 0.0120 and 0.015 m 3 /s. These flow rates were converted to superficial velocities and used as boundary conditions at the inlet of the pipe. The simulation was validated by bench marking with a Baker chart, and it had successfully predicted the slug parameters. The computational fluid dynamics simulation results revealed that the slug length and pressure were increasing as the air superficial velocity increased. The slug initiation position was observed to end up being shifted to a closer position to the inlet. It was believed that the strength of the slug was high at the initiation stage and reduced as the slug progressed to the end of the pipe. The pressure gradient of the flow was realised to increase as the gas flow rate was increasing, which in turn was a result of the higher mean velocity.

Nowadays, many industrial and modern applications depend on heat transport in porous zones. An experimental study of the natural convection heat transfer in a corrugated cavity with dimensions of (200, 250, 300) mm in length, a width of 200 mm, a depth of 27 mm, and an amplitude of 30 mm was filled with porous materials: glass balls (3, 6, 10) mm and alumina balls (6) mm, where the water was the working fluid. The top surface was exposed to the environment, while the bottom surface was subjected to constant heat flux (300, 500, 700, 900, 1100 W/m2), The front face, back face, and sides were insulated. In this study, temperature distribution, modified Rayleigh number, and Nusselt number values are foremost criteria, which are presented for three levels of aspect ratio. The influence of various aspect ratios on heat transfer is investigated. The results showed that the heat transfer coefficient decreases with the increase in aspect ratio. The highest value is when aspect ratio = 1. The enhanced Rayleigh number decreases as the aspect ratio increases by 10%.

The sustainable transportation of liquid fuels in a piping system can be interrupted due to slug flow, which causes the severe unsteady loading on pipelines. A feature that is particularly affected by this problem is the oil transportation pipeline, where gas is often combined with the produced oil. In order to fully understand the behavior of such flows, it is imperative to simulate the effective zones along the span of the pipelines. This will allow the designer of the piping system to estimate the required pumping power through the evaluation of the pressure drop in the slug oil/gas flow. This paper reports the oil/gas flow phenomena in a horizontal pipe with a large diameter of 0.16 m, with 3-dimensional, transient, incompressible fluids, utilizing STAR-CCM+ commercial software. The volume of fluid (VOF) model was adopted to track the interface between the two phases. The operational conditions for the cases studied were extracted for the slug zone from the Baker chart. The slug flow was achieved accordingly, which gives us granted validation with the experimental source. The numerical procedure allowed the determination of the pressure drop. Also, the transient behavior of the slug flow was predicted through the tracking of the slug development in the pipe segment. Moreover, the proposed model could be extended to simulate other types of two-phase flow regimes.

No abstract