Compressible fluids impact pressure

The forces associated with slug flow of cryogenic fluids are considerably less than those calculated because of the effect of gas evolution. The compressible gas present in the flow stream absorbs energy and cushions the hammer at an elbow. Also, the elasticity of the pipe will reduce the effective velocity of a sonic pressure wave by about l io and consequently reduce the head rise at an elbow. The use of long-sweep elbows also reduces impact pressures by increasing the impact area. 

For two-phase flow, heat gain/loss is also an important consideration, because this dictates the vapor/liquid fraction of the flow. Apart from changing the overall physical properties, this also changes the flow regime and will have a substantial impact in pressure drop calculation. The heat loss/ gain can be used for compressible fluids for better results however, it is of less importance for multiphase flow, unless the thermodynamic correlations are used to estimate the vapor/liquid fraction of the fluid. 

Devices which are used for transporting fluids (liquids and gases) may be divided into pumps, ejectors, injectors, elevators, conveyors, air and gas pressure devices (such as acid eggs, air lifts, pulsometers etc). Pumps may be divided into piston (reciprocating), centrifugal, propeller, rotary-displacement, density, impact and momentum and turbine pumps. Pumps which are used for compressing gases are called "compressors ... 

The simulated evolution of compressive stress in the buffer is very similar for CEA and KTH, whereas CNSC obtained a substantially higher compressive stress (Figure 5c). The results by CEA and KTH indicate that the impact of the fluid pressure restoration is a dominant component contributing about 90% of the total compressive stress. 

The cell compressive strain (Fig. 2) was maximal at the 5 %/s loading rate, and was smallest when loaded at the impact loading rate (500%/s). Fluid pressure changes in the cells (Fig. 3) increased about 50 times when loading rates were increased from 0.17 %/s to 500 %/s. 

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