Bulk kinetic energy

The contents of a process vessel will be subject to some degree of turbulence or mixing, and so we may normally regard their bulk velocity, gas or liquid, as zero. Thus 

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The quantity is the bulk kinetic energy of the system in the lab frame—that is, the... 

SOLUTION Can you draw a schematic of this process We need to write the energy balance. This system is at steady-state, with one stream in and one stream out. When working with macroscopic potential energy, it is often convenient to write the balance on a mass (rather than mole) basis. We will neglect the bulk kinetic energy of the water at the inlet and outlet and the heat loss through the pipe. Since there are no frictional losses, the exit temperature is the same as the inlet therefore, their enthalpy is equal. Thus, the first law simplifies to ... 

This example has two inlet streams in, so Equation (2.50) does not apply. If we assume that the rate of heat transfer and the bulk kinetic energy of the streams are negligible and the bulk potential energy and shaft work are set to zero, an energy balance reduces to ... 

A steady-state energy balance with one stream in and one stream out is appropriate for this system. We will assume that the bulk kinetic energy of the stream is negligible and that the porous plug is sufficiently small as not to allow a significant rate of heat transfer. Rewriting Equation (2.50) on a mass basis, we get ... 

The Permeation Process Barrier polymers limit movement of substances, hereafter called permeants. The movement can be through the polymer or, ia some cases, merely iato the polymer. The overall movement of permeants through a polymer is called permeation, which is a multistep process. First, the permeant molecule coUides with the polymer. Then, it must adsorb to the polymer surface and dissolve iato the polymer bulk. In the polymer, the permeant "hops" or diffuses randomly as its own thermal kinetic energy keeps it moving from vacancy to vacancy while the polymer chains move. The random diffusion yields a net movement from the side of the barrier polymer that is ia contact with a high concentration or partial pressure of the permeant to the side that is ia contact with a low concentration of permeant. After crossing the barrier polymer, the permeant moves to the polymer surface, desorbs, and moves away. 

The major variable in setting entrainment (E, weight of liquid entrained per weight of vapor) is vapor velocity. As velocity is increased, the dependence of E on velocity steepens. In the lowest velocity regime, E is proportional to velocity. At values of E of about 0.001 (around 10 percent of flood), there is a shift to a region where the dependence is with (velocity) ". Near flood, the dependence rises to approximately (velocity). In this regime, the kinetic energy of the vapor dominates, and the bulk of the dispersion on the plate is often in the form of a coarse spray. 

In addition to primary features from copper in Eig. 2.7 are small photoelectron peaks at 955 and 1204 eV kinetic energies, arising from the oxygen and carbon Is levels, respectively, because of the presence of some contamination on the surface. Secondary features are X-ray satellite and ghost lines, surface and bulk plasmon energy loss features, shake-up lines, multiplet splitting, shake-off lines, and asymmetries because of asymmetric core levels [2.6]. 

The kinetic energy kin A (see Fig. 1), however, will be measured by use of an analyzer and may differ at the analyzer from the kinetic energy Ekin the electron had at the sample. Therefore the work function A of the analyzer, which can be considered as constant for a given measuring period, has to be used in equation (2). The work function of the sample has no influence in this simple picture on the kinetic energy measured for an electron excited from the bulk of the sample, because fikin is measured with respect to r/>A of the analyzer. 

Fig. 30. XPS core level (Cu2p) shifts for copper deposited on Pt. Different symbols correspond to separate experiments (new electrolyte, new electrode). Arrows indicate kinetic energy of bulk Cu and reversible potential for Cu deposition respectively. MgKa source.

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