Multi-phase Flow: Complex Flow Regimes and Phase Behaviours
We use a variety of test fluids to simulate mixtures of liquids and gases. Liquids usually include combinations of water and oil either in segregated flow or as emulsions. Gases used in flow testing are generally inert and non-condensable under the test conditions. The most complex flow tests include conditions where components of the test fluids change phase: vaporizing at one point and condensing at another. In most industrial applications, water is the most likely to change phases. Liquid hydrocarbons and liquids with dissolved gases can also show very complex behaviours under pressure and temperature conditions that are common in industry.
Water: Phase Changes and Steam Quality
We test equipment over a range of pressure and temperature conditions where water may exist as a liquid or steam. Some tests require precise control of the ratio of gaseous to liquid water (steam quality) to mimic field conditions. Other tests monitor pressure and temperature to determine how changing operating conditions affect how much steam is present. This allows us to evaluate phenomena like steam flashing and gas locking in high temperature pumps. The liquid water phase in a flow test can also include a variety of additives to change the behaviour of the water. Chemical additives are used to increase density, change pH, increase viscosity or impede or stabilize emulsions.
Oil: Everything from Canola to Diluted Bitumen
We use stable, refined oil products to ensure repeatability in testing programs. Where high viscosity liquids are required, we use silicone oils prepared with specific viscosity characteristics. Heat transfer oil is used for high-temperature applications to minimize vaporization and fire hazards. Flammable products such as crude oil, diluted bitumen, oil-based drilling mud and refined petroleum products can also be used for testing. “Edible oils” have been used in some instances where environmental exposure concerns are heightened but these products are not generally stable for long-duration testing programs.
Gas: Non-condensable but Soluble
We typically use nitrogen for the gas phase in tests in place of more hazardous gases such as methane, carbon dioxide and hydrogen sulfide. Even air can be hazardous at high pressure as there may be residual oil products in the flow loop that could auto-ignite at high pressure. Using an inert gas greatly reduces safety concerns and minimizes corrosion damage to the test setup.
Hazardous gases are required in some tests to properly represent the flow characteristics. This can include:
- Partial pressure and phase change behaviour in the presence of other components, such as steam;
- Solubility of the gas in the liquid phase; and
- Corrosion of equipment components.