Conduit gases

Laser Doppler Velocimeters. Laser Doppler flow meters have been developed to measure Hquid or gas velocities in both open and closed conduits. Velocity is measured by detecting the frequency shift in the light scattered by natural or added contaminant particles in the flow. Operation is conceptually analogous to the Doppler ultrasonic meters. Laser Doppler meters can be appHed to very low flows and have the advantage of sensing at a distance, without mechanical contact or interaction. The technique has greatest appHcation in open-flow studies such as the deterrnination of engine exhaust velocities and ship wake characteristics. 

Circulating fluidized beds (CFBs) are high velocity fluidized beds operating well above the terminal velocity of all the particles or clusters of particles. A very large cyclone and seal leg return system are needed to recycle sohds in order to maintain a bed inventory. There is a gradual transition from turbulent fluidization to a truly circulating, or fast-fluidized bed, as the gas velocity is increased (Fig. 6), and the exact transition point is rather arbitrary. The sohds are returned to the bed through a conduit called a standpipe. The return of the sohds can be controUed by either a mechanical or a nonmechanical valve. 

Explosion-proof enclosures are characterized by strong metal enclosures with special close-fitting access covers and breathers that contain an ignition to the inside of the enclosure. Field wiring in the hazardous environment is enclosed in a metal conduit of the mineral-insulated-cable type. All conduit and cable connections or cable terminations are threaded and explosion-proof. Conduit seals are put into the conduit or cable system at locations defined by the National Electric Code (Article 501) to prevent gas and vapor leakage and to prevent flames from passing from one part of the conduit system to the other. 

Pipe Lines For quantities of fluid which an economic investigation indicates are sufficiently large and continuous to justify the investment, pipe lines are one of the lowest-cost means of transportation. They have been built up to 1.22 m (48 in) or more in diameter and about 3200 km (2000 mi) in length for oil, gas, and other products. Water is usually not transported more than 160 to 320 km (100 to 200 miles), but the conduits may be much greater than 1.22 m (48 in) in diameter. Open canals are also used for water transportation. 

In 110-kV high-voltage grids, gas pressure cables (external and internal gas pressure cables) are mainly laid in steel conduit. In service, the steel pipe is filled with nitrogen at a gas pressure of 15 to 16 bar. Figure 14-1 shows the cross-section of such an external gas pressure cable. 

ISO 4053-1 1977. Measurement of Gas Flow in Conduits—Tracer Methods—Part 1 Cjcncrai. International Organisation for Standardisation, 1977. 

Flow The movement of a vapor, fluid, sludge, or gas in a conduit. The flow may be forced or due to gravity. 

Prevent process gas or liquid in process piping from entering conduit or cable systems. 

Except for conduit or cable entries into explosion-proof enclosures containing arcing or high-temperature devices (as described in Item I above), cables that will leak gas through the core at a rate of less than 0.007 ft /hr at 6 in. of water pressure need not be sealed if they are provided with a continuous gas/vapor-tight sheath. Cables with such a sheath that will transmit gas at or above this rate must be sealed if connected to process equipment that may cause a pressure of 6 in. of water at the cable end. 

In another incident a backhoe ruptured a 3-in. polyethylene natural gas pipeline fortunately the gas did not ignite. The drawings were complex and cluttered, and the contractor overlooked the pipeline. A metal detector was not used. This would have detected the pipe as a metal wire was fixed to it, a good practice. In a third incident a worker was hand-digging a trench, as an electric conduit was believed to be present. It was actually an old transfer line for radioactive waste, and he received a small dose of radioactivity. The planner had misread the drawing. 

Kanal, m. canal channel conduit sewer flue tunnel, -gas, n. sewer gas. 

Kanalisations-rohr, n., -rohre, /. sewer pipe, water pipe, gas pipe, or electric conduit. 

Oil and gas are usually associated with sedimentary rocks. The three basic types of sedimentaiy rocks are shales, sands, and carbonates. The shales are the sources of the hydrocarbons while the sands and carbonates act as the conduits and/or the containers. 

Most of heat transfer correlations are based on data obtained in flow boiling from relatively large diameter conduits and the predictions from these correlations show considerable variability. Effects of superficial liquid and gas velocity on heat transfer in gas-liquid flow and its connection to flow characteristics were studied by Hetsroni et al. (1998a,b, 2003b), Zimmerman et al. (2006), Kim et al. (1999), and Ghajaret al. (2004). However these investigation were carried out for tubes of D = 25—42 mm. These data, as well as results presented by Bao et al. (2000) in tubes of L> = 1.95 mm and results obtained by Hetsroni et al. (2001), Mosyak and Hetsroni (1999) are discussed in the next sections to clarify how gas and liquid velocities affect heat transfer. Effects of the channel size and inclination are considered. 

Bao ZY, Fletcher DF, Haynes BS (2000) An experimental study of gas-liquid flow in a narrow conduit. Int J Heat Mass Transfer 43 2313-2324... 

The liquid enters the micro channel device via a large bore that is connected to a micro channel plate via a slit (Figure 5.2). The slit acts as a flow restrictor and serves for equipartition of the many parallel streams [1, 3, 4]. The liquid streams are re-collected via another slit at the end of the micro structured plate and leave the device by a bore. The gas enters a large gas chamber, positioned above the micro channel section, via a bore and a diffuser and leaves via the same type of conduit. 

Certain alkylated ammonium, phosphonium, or sulfonium compounds are effective, in relatively low concentrations, in interfering with the growth of gas hydrate crystals [972] and therefore are useful in inhibiting plugging by gas hydrates in conduits containing low-boiling hydrocarbons and water. For example, tetrabutylammonium bromide will be active. Gas hydrate or ice formation is further inhibited in lines by adding amino acids or amino alcohols [523]. 

Dispersantfor Sulfur. The deposition of elemental sulfur in conduits through which a sulfur-containing gas is flowing can be reduced by providing a sulfur dispersant. The dispersant is an adduct of a primary alcohol and epichloro-hydrin, mixed with an aliphatic amine component [554]. 

The gas phase exists as a continuum in the central core of the conduit, and the liquid phase exists as a continuous film along the tube wall and as droplets in the gas phase. New droplets are continually being formed at the gas-liquid interface. The motion of the gas phase accelerates the droplets to a velocity approaching that of the gas phase. Droplets in the central core... 

In part II of the present report the nature and molecular characteristics of asphaltene and wax deposits from petroleum crudes are discussed. The field experiences with asphaltene and wax deposition and their related problems are discussed in part III. In order to predict the phenomena of asphaltene deposition one has to consider the use of the molecular thermodynamics of fluid phase equilibria and the theory of colloidal suspensions. In part IV of this report predictive approaches of the behavior of reservoir fluids and asphaltene depositions are reviewed from a fundamental point of view. This includes correlation and prediction of the effects of temperature, pressure, composition and flow characteristics of the miscible gas and crude on (i) Onset of asphaltene deposition (ii) Mechanism of asphaltene flocculation. The in situ precipitation and flocculation of asphaltene is expected to be quite different from the controlled laboratory experiments. This is primarily due to the multiphase flow through the reservoir porous media, streaming potential effects in pipes and conduits, and the interactions of the precipitates and the other in situ material presnet. In part V of the present report the conclusions are stated and the requirements for the development of successful predictive models for the asphaltene deposition and flocculation are discussed. 

That is, as P2 decreases, the mass velocity will increase up to a maximum value of G, at which point the velocity at the end of the pipe reaches the speed of sound. Any further reduction in the downstream pressure can have no effect on the flow in the pipe, because the speed at which pressure information can be transmitted is the speed of sound. That is, since pressure changes are transmitted at the speed of sound, they cannot propagate upstream in a gas that is already traveling at the speed of sound. Therefore, the pressure inside the downstream end of the pipe will remain at P 2, regardless of how low the pressure outside the end of the pipe (P2) may fall. This condition is called choked flow and is a very important concept, because it establishes the conditions under which maximum gas flow can occur in a conduit. When the flow becomes choked, the mass flow rate in the pipe will be insensitive to the exit pressure but will still be dependent upon the upstream conditions. 

The adiabatic flow of an ideal gas flowing through a frictionless conduit or a constriction (such as an orifice nozzle, or valve) can be analyzed as follows. The total energy balance is... 

Until recently, epithelial cells were considered to function solely as the ciliated barrier lining in the airways and as conduits for gas exchange at the air/blood interphase. As techniques have improved to isolate and culture these cells and measure their gene products, it has become clear that they have a key role in lung defense and repair. Epithelial cells secrete a number of anti-microbial compounds and immunoregulatory cytokines [52], and are also capable of ingesting and killing bacteria [53],... 

Kling, G.W., Kipphut, G. W. Miller, M.C. 1991. Arctic lakes and streams as gas conduits to the atmosphere Implications for tundra carbon budgets. Science, 251, 298-301. 

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