The Flow of Gases

Here m is the mass of a molecule with an effective diameter of re and a mean speed of c (which of course is also a function of mass). This equation was first derived by Maxwell in 1860. We can immediately see the importance of the nature of the molecules through their mass and through the effective diameter, which is not just a geometric size but includes a contribution from the interaction with its neighbours. 

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For the flow of gases, expansion factor Y, which allows for the change in gas density as it expands adiabaticaUy from pi to po, is given by... 

Experience has shown that the concave-upward type is a better arrangement than the concave-downward type, as it tends to increase the flow of gases in the outer portion of the bed. This counteracts the normal tendency of higher gas flows in the center of the bed. 

Piping, manifolds, switching valves and controls to direct and control the flow of gases according to the process requirements. 

Wliere possible, all flame arresters should be installed so that the elements will be self-draining. If liquid can accumulate in the housing, provision should be made to drain any accumulated liquid that could block the flow of gases through the flame arrester. 

Aerodynamics deals with the flow of gases, particularly air, and the interaction with objects immersed in the flow. The interaction takes the form of an aerodynamic force and moment exerted on the object by the flow, as well as heat transfer to the object (aerodynamic heating) when the flow velocities exceed several times the speed of sound. 

In this chapter consideration is given to the flow of gases through orifices and nozzles, and to flow in pipelines. It is found that, in all these cases, the flow may reach a limiting maximum value which is independent of the downstream pressure this is a phenomenon which does not arise with incompressible fluids. 

The hot-wire anemometer is very accurate even for very low rates of flow. It is one of the most convenient instruments for the measurement of the flow of gases at low velocities accurate readings are obtained for velocities down to about 0.03 m/s. If the ammeter has a high natural frequency, pulsating flows can be measured. Platinum wire is commonly used. 

Gamso.v B.W., Thodos. G. and Hougfn. O.A. Trans Am. Inst. Chem. Eng. 39 (1943) 1. Heat mass and momentum transfer in the flow of gases through granular solids. 

Experience has shown that a concave-downward (Fig. 17-10f) gas distributor is a better arrangement than a concave-upward (Fig. 17-10-e) gas distributor, as it tends to increase the flow of gases in the outer ortion of the bed. This counteracts the normal tendency of the gas to ow into the center of the bed after it exits the gas distributor. In addition, the concave-downward type of gas distributor tends to assist the eneral solids flow pattern in the bed, which is up in the center and own near the walls. The concave-upward gas distributor tends to have a slow-moving region at the bottom near the wall. If solids are large (or if they are slightly cohesive), they can build up in this region. 

In Section 3.13 the characteristics of low-speed flows (low Mach number) are discussed further. Even in the flow of gases, where temperature and species variations cause large density variations, low-speed flows still retain some very useful attributes of incompressible flow. 

Baffles are built in coagulation basins to impede the flow of liquids, and are also found in exhaust mufflers, where their purpose is to mix the flow of gases in adjacent exhaust puffs so that they may emerge from the muffler in a silent steady stream. 

A sample of 41 Ar, a radioisotope used to measure the flow of gases from smokestacks, decays initially at a rate of 34,500 disintegrations/min, but the decay rate falls to 21,500 disintegrations/min after 75.0 min. What is the half-life of 41Ar ... 

The flow of gases from a smokestack can be measured by releasing 41 Ar and monitoring its passage. 

To demonstrate the capability of the code to handle different mass flow rates among the cells, hypothetical cases are simulated where the flow of gases is redistributed such that a few randomly selected cells receive lesser flow rates than the rest of the cells in the stack. The total flow rate to the stack, however, is same as in the base line presented above. These cases are representative of some of the cells in a stack being partially blocked due to say clogging. The results shown in Figure 5.29 correspond to the case where three cells are partially blocked, allowing only 70% of... 

Chapter 2 acknowledges the fact that in the design of vacuum systems, pump sets and pipework of an appropriate size must be used and that it is vital that the flow of gases into and out of the system be quantified. Terms widely used in vacuum technology are defined and the calculation of flow and related quantities under the three major types of gas flow is discussed. 

The flow of gases through beds of broken solids. U. S. Bur. Mines Rept Investigations 2904. 

For the flow of gases, the two boundary layer thicknesses are generally, approximately equal. For the flow of liquids, however, the two thicknesses are generally... 

Basic equations for the design and operation of orifice meters, venturi meters, and rotameters can be derived from the total energy balances presented at the beginning of this chapter. The following equations apply when the flowing fluid is a liquid, and they also give accurate results for the flow of gases if the pressure drop caused by the constriction is less than 5 percent of the upstream pressure ... 

Status reviews on multiple step cycles have been presented,46,47 and include the leading candidates GA s 3-step cycle based on the thermal decomposition of H2SO4 at 1130 K,48 and the UT3 s 4 step cycle based on the hydrolysis of CaBn and FeBn at 1020 and 870 K 49 This process involving two Ca and two Fe compounds has received some attention.4 The process is operated in a cyclic manner in which the solids remain in their reaction vessels and the flow of gases is switched when the desired reaction extent is reached ... 

There are methods for measuring the surface area using the flow of gases through a porous medium, by finding a pressure drop across the particle. The equation relating the mole gas flow rate J and the pressure drop AP can be written as [13]... 

The flow of gases and simple liquids can be described by a single property the shear viscosity or viscosity for short. You can measure the viscosity by shearing the liquid between two parallel plates (as in Figure C4-1). This causes a velocity gradient normal to the direction of the motion (also known as the shear rate). The viscosity is the ratio of the shear stress to the... 

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