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In fluid measurement, the fluid's flow conditions (or flowing conditions) refer to quantities like temperature and static pressure of the metered substance. The flowing conditions are required data in order to calculate the density of the fluid at flowing conditions. The flowing density is in turn required in order to compensate the measured volume to quantity at base conditions.
The density of a gas is calculated using the ideal gas law and an equation of state calculation such as the one described in AGA Report No. 8.
There are broad general methodologies used to calculate the density of a liquid at specific conditions. In order to discuss a specific methodology, one must choose a liquid that holds sufficient interest to warrant a calculation specific to it. EOS 87.3 is a density calculation for seawater; API chapter 11 specifies calculations pertaining to oil, fuels and natural gas liquids.
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The density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics and hydrodynamics. Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.
A turbine (from the Greek τύρβη, tyrbē, meaning "vortex", related to the Latin turbo, meaning a vortex, is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating electrical power when combined with a generator. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels.
In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid's potential energy. The principle is named after Daniel Bernoulli who published it in his book Hydrodynamica in 1738. Although Bernoulli deduced that pressure decreases when the flow speed increases, it was Leonhard Euler who derived Bernoulli's equation in its usual form in 1752. The principle is only applicable for isentropic flows: when the effects of irreversible processes and non-adiabatic processes are small and can be neglected.
Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. The common types of flowmeters with industrial applications are listed below:
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems. Ongoing research yields software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows. Initial validation of such software is typically performed using experimental apparatus such as wind tunnels. In addition, previously performed analytical or empirical analysis of a particular problem can be used for comparison. A final validation is often performed using full-scale testing, such as flight tests.
Permeability in fluid mechanics and the Earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.
A gas meter is a specialized flow meter, used to measure the volume of fuel gases such as natural gas and liquefied petroleum gas. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, because measured volumes are highly affected by temperature and pressure. Gas meters measure a defined volume, regardless of the pressurized quantity or quality of the gas flowing through the meter. Temperature, pressure, and heating value compensation must be made to measure actual amount and value of gas moving through a meter.
Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum.
Originally the gas flow computer was a mechanical or later a pneumatic or hydraulic computing module, subsequently superseded in most applications by an electronic module, as the primary elements switched from transmitting the measured variables from pneumatic or hydraulic pressure signals to electric current as explosion-proof ) and then intrinsically safe transmitters became available, that simply provided a dedicated gas flow computer function. Today "gas flow computers" as such have become uncommon, since gas flow computing is a subfunction of a data acquisition and control program implemented with programmable logic controller (PLCs) and remote terminal unit (RTUs); with the rise of smart transmitters in the early 1980s, these functions have also been incorporated within the field transmitters themselves.
Choked flow is a compressible flow effect. The parameter that becomes "choked" or "limited" is the fluid velocity.
The plug flow reactor model is a model used to describe chemical reactions in continuous, flowing systems of cylindrical geometry. The PFR model is used to predict the behavior of chemical reactors of such design, so that key reactor variables, such as the dimensions of the reactor, can be estimated.
Gas kinetics is a science in the branch of fluid dynamics, concerned with the study of motion of gases and its effects on physical systems. Based on the principles of fluid mechanics and thermodynamics, gas dynamics arises from the studies of gas flows in transonic and supersonic flights. To distinguish itself from other sciences in fluid dynamics, the studies in gas dynamics are often defined with gases flowing around or within physical objects at speeds comparable to or exceed the speed of sound and causing a significant change in temperature and pressure. Some examples of these studies include but are not limited to: choked flows in nozzles and valves, shock waves around jets, aerodynamic heating on atmospheric reentry vehicles and flows of gas fuel within a jet engine. At the molecular level, gas dynamics is a study of the kinetic theory of gases, often leading to the study of gas diffusion, statistical mechanics, chemical thermodynamics and non-equilibrium thermodynamics. Gas dynamics is synonymous with aerodynamics when the gas field is air and the subject of study is flight. It is highly relevant in the design of aircraft and spacecraft and their respective propulsion systems.
In fluid flow, friction loss is the loss of pressure or “head” that occurs in pipe or duct flow due to the effect of the fluid's viscosity near the surface of the pipe or duct. In mechanical systems such as internal combustion engines, the term refers to the power lost in overcoming the friction between two moving surfaces, a different phenomenon.
A flow computer is an electronic computer which implements algorithms using the analog and digital signals received from flow meters, temperature, pressure and density transmitters to which it is connected into volumes at base conditions. They are used for custody or fiscal transfer.
Custody Transfer in the oil and gas industry refers to the transactions involving transporting physical substance from one operator to another. This includes the transferring of raw and refined petroleum between tanks and tankers; tankers and ships and other transactions. Custody transfer in fluid measurement is defined as a metering point (location) where the fluid is being measured for sale from one party to another. During custody transfer, accuracy is of great importance to both the company delivering the material and the eventual recipient, when transferring a material.
Base conditions, also known as standard conditions, consist of a specified absolute pressure and temperature. To ensure accuracy, it is important to refer to base conditions when measuring the volume of a sample of liquid or gas. This applies to both static measurement and flow measurement.
In fluid mechanics, a shell balance can be used to determine how fluid velocity changes across a flow.
Gas is one of the four fundamental states of matter. A pure gas may be made up of individual atoms, elemental molecules made from one type of atom, or compound molecules made from a variety of atoms. A gas mixture, such as air, contains a variety of pure gases. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible, as indicated by the constant velocity vectors in the image.
The flow in many fluids varies with density and depends upon the gravity. Due to which the fluid with lower density is always above the fluid with higher density. Stratified flows are very common such as the Earth's ocean and its atmosphere.