Datum head

The driving force associated with the seepage velocity v is the reduced Bernoulli potential, which consists of the pressure head and the datum head thus Darcy s law takes the form... 

NPSHR) The NPSH, iu meters (feet), deterruiued by veu-dor testing with water. NPSHR is measured at the suction flange and corrected to the datum elevation. NPSHR at rated and other capacities is equal to the NPSH that produces a 3 percent head drop (first stage head in multistage pumps) due to cavitation within the pump. 

Once the hydrocarbons have been solubilized in the formation water, they move with the water under the influence of elevation and pressure (fluid), thermal, electroosmotic and chemicoosmotic potentials. Of these, the fluid potential is the most important and the best known. The fluid potential is defined as the amount of work required to transport a unit mass of fluid from an arbitrary chosen datum (usually sea level) and state to the position and state of the point considered. The classic work of Hubbert (192) on the theory of groundwater motion was the first published account of the basinwide flow of fluids that considered the problem in exact mathematical terms as a steady-state phenomenon. His concept of formation fluid flow is shown in Figure 3A. However, incongruities in the relation between total hydraulic head and depth below surface in topographic low areas suggested that Hubbert s model was incomplete (193). Expanding on the work of Hubbert, Toth (194, 195) introduced a mathematical mfcdel in which exact flow patterns are... 

Either Qi or Q2 or both may be variable and functions of z, or one of the two may be either constant or zero. For example, if liquid is discharged through an orifice or a pipe of area A under a differential head z, Q2 = Cd (2gz)m, where Cd is a numerical discharge coefficient and z is a variable. If the liquid flows out over a weir or a spillway of length B, Q2 = CBz3/2, where C is the appropriate coefficient. (For steady flow, z would be the constant H.) In either case z is the variable height of the liquid surface above the appropriate datum. In like manner, Qi may be some function of z. 

With point 1 as the datum, Z2 is equal to 0. hp is the head loss in the suction side from point 1 to the inlet of the pump and hf is the head loss in the discharge side from the outlet of the pump to point 2. Because the distances are very short, they can be neglected compared to the other terms in the equation. Pg is equal to the gage pressure at point 2, Pgs, plus the barometric pressure. In terms of P b, Pb is then equal to PgB + Pam- The most complete treatment will also include the vapor pressure of water. Neglecting vapor pressure since it is negligible, however, the previous... 

Static Head. Fluid elevation above or below the datum line. For horizontal centrifugal pumps, static head is calculated from the pump center line with vertical pumps, it is taken from the eye of the first-stage impeller. 

Suction Lift. The manometer reading in feet of liquid at the pump suction (corrected to a datum), minus the velocity head. This term expresses the suction head when it is below atmospheric pressure. 

Except where noted, the pressure in the quenching chamber is kept at 350 =b 20 torr. The actual pressure of each sample is known to 1 torr but that is not a significant datum in the analysis and is used only as a consistency check. Quench section pressure measures intermediate section pressures fairly well, but probably not the arc pressures because of the pressure drop through the front orifice of the plasma jet. These arc units are not instrumented to measure the pressure inside the head. 

Every term in Eq. 5.11 has the dimension of a length. The lengths are at least conceptually convertible to elevation Az above some datum plane. These elevations are commonly referred to as heads Thus, we refer to the various... 

This head is graduated from 0° to 180°, is adjustable through this range, and is used when scribing lines at an angle to a workpiece datum. 

Using an equation of equilibrium or motion, which determines the deformation of the solid skeleton, and (5.58), a system of differential equations for specifying the mean velocity v (i.e., the conventional consolidation problem) is achieved. Note that in (5.58)

total head excluding the velocity potential), k is the hydraulic conductivity tensor, p is the pore pressure of the fluid, g is the gravity constant, and is the datum potential. Thus by starting with the mass conservation laws for both fluid and solid phases, we can simultaneously obtain the diffusion equation and the seepage equation which includes a term that accounts for the volumetric deformation of the porous skeleton. 

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