Liquids pressure

Cavitation Loosely regarded as related to water hammer and hydrauhc transients because it may cause similar vibration and equipment damage, cavitation is the phenomenon of collapse of vapor bubbles in flowing liquid. These bubbles may be formed anywhere the local liquid pressure drops below the vapor pressure, or they may be injected into the hquid, as when steam is sparged into water. Local low-pressure zones may be produced by local velocity increases (in accordance with the Bernouhi equation see the preceding Conservation Equations subsection) as in eddies or vortices, or near bound-aiy contours by rapid vibration of a boundaiy by separation of liquid during water hammer or by an overaU reduction in static pressure, as due to pressure drop in the suction line of a pump. 

In addition to the surface area of the particles, several other parameters have some influence on the necessary resin consumption, e.g. the type of the boards, thickness of the sanding zone, type and capacity of the blenders, separation and spraying of the glue resin (only wiping effect or spraying of the resin by air or liquid pressure), shape of the panicles for the same particle sizes, dependence of... 

Head loss The reduction in liquid pressure associated with the passage of a solution through a bed of exchange material a measure of the resistance of a resin bed to the flow of the liquid passing through it. 

The type of reaetor is seleeted in the light of numerous faetors sueh as volume ratio of gas to liquid, pressure drop, heat transfer and mixing intensity. 

The aerated liquid pressure drop includes that generated by forming bubbles [193] due to surface tension effects. The equivalent height of clear liquid on the tray is given [193] ... 

Figure 8-149. Correlation for aerated-tray-liquid pressure drop developed from published data for various valves. Note (j> = relative froth density. Reference numbers are from original article [201 ]. Used by permission, Klein, G. F., Chem. Eng. V. 89, No. 9 (1982), p. 81 all rights reserved.

Aerated tray, liquid pressure drop or equivalent clear liquid on tray, in. tray liquid Height of clear liquid on inlet side of tray, in. Height of clear liquid at overflow weir, in. 

Cap assembly partial pressure drop, including drop through riser, reversal, annulus, slots, in. liquid Pressure drop through risers, in. liquid Pressure drop through reversal and annulus, in. liquid... 

The vertical thermosiphon reboiler is a popular unit for heating distillation column bottoms. However, it is indeed surprising how so many units have been installed with so little data available. This indicates that a lot of guessing, usually on the very conservative side, has created many uneconomical units. No well-defined understanding of the performance of these units exists. Kern s recommended procedure has been found to be quite conservative on plant scale units yet it has undoubtedly been the basis for more designs than any other single approach. For some systems at and below atmospheric pressure operation, Kern s procedure gives inconsistent results. The problem is in the evaluation of the two-phase gas-liquid pressure drop under these conditions. 

Figure 10-136. Tube-side liquid pressure drop for cascade cooler. For nonwater liquids, multiply pressure drop by (n, ) " (s) (Used by permission SGL Technic, Inc., Karbate Division.)...

The bund walls must be oil proof and be capable of withstanding considerable liquid pressure in the event of an overflow or other emergency. No permanent drain must be incorporated into a bund area, but suitable facilities should be provided to remove rainwater that may accumulate. A sump and semi-rotary hand pump are suitable for this purpose. 

Face lubricated-type seals must be connected from the source of lubrication to the tap openings in the seal gland before startup. This is another predetermined environmental control feature that is mandatory for proper seal function. Where double seals are to be operated, it is necessary that the lubrication feed lines be connected to the proper ports for both circulatory or dead-end systems before equipment startup. This is very important because all types of double seals depend on the controlled pressure and flow of the sealing fluid to function properly. Even before the shaft is rotated, the sealing liquid pressure must exceed the product pressure opposing the seal. Be sure a vapor trap does not prevent the lubricant from reaching the seal face promptly. 

It is seen in figure (4) that the total air pressure on the piston, diameter (y), is transferred to a piston controlling the liquid pressure of diameter (x). Because the radii of the pistons differ, there will be a... 

The calculations show that the liquid pressure monotonically decreases along the heating region. Within the evaporation region a noticeable difference between the vapor and liquid pressures takes place. The latter is connected with the effect of the Laplace force due to the curvature of the interface surface. In the superheated region the vapor pressure decreases downstream. 

The effect of various parameters on the difference between vapor and liquid pressure is illustrated in Figs. 8.3 and 8.4. The effect of the Fuler and Weber numbers as well as the thermal parameter is highly noticeable. An increase in Fu, We and d- leads to a decrease in AP, whereas the difference of both phase pressures is practically independent of Reynolds number. An increase in the Froude number is accompanied by an increase in AP for a small Fr. At Fr > 10 the effect of Fr on AP is negligible. 

The effect of gravity on the liquid and vapor parameters in the inlet and outlet cross-section is presented in Figs. 8.12 and 8.13. It is seen that an increase in the gravity is accompanied by a significant growth of the liquid pressure (Fig. 8.12a). At the same time an increase of the vapor pressure in the outlet cross-section is observed. However, the rate of liquid and vapor pressure growth are very different. This causes an increase of the difference AP = gravity... 

Fig. 8.12a,b The effect of gravity on inlet liquid pressure and pressure difference between the inlet and outlet cross-section of the capillary (a) the dependence of (g), (b) the dependence of AP(g), (AP = — Pout). Reprinted from Peles et al. (2000) with permission... 

The vapor pressure, density and temperature practically do not change along the evaporation region in physieally realistic systems. The latter allows one to simplify the system of governing equations and reduce the problem to a successive solution of the shortened system of equations to determine the velocity, liquid pressure and gaseous phases as well as the interface shape in a heated capillary. 

At the interface the mass and thermal balance equations are valid. If one assumes that the liquid-vapor interface curvature is constant, accordingly (7)3-71)1111 = c/T men, Where Pq and Pl are the vapor and liquid pressure at the interface, a is the surface tension, and/ men is the meniscus radius. 

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