Mass-velocity

A bimoleciilar reaction can be regarded as a reactive collision with a reaction cross section a that depends on the relative translational energy of the reactant molecules A and B (masses and m ). The specific rate constant k(E ) can thus fonnally be written in tenns of an effective reaction cross section o, multiplied by the relative centre of mass velocity... 

Here one has the thennal average centre of mass velocity... 

In a sector instrument, which acts as a combined mass/velocity filter, this difference in forward velocity is used to effect a separation of normal and metastable mj" ions (see Chapter 24, Ion Optics of Magnetic/Electric-Sector Mass Spectrometers ). However, as discussed above, the velocity difference is of no consequence to the quadmpole instrument, which acts only as a mass filter, so the normal and metastable mj ions formed in the first field-free region (Figure 33.1) are not differentiated. 

Scanning method. The sequence of control over operating parameters of a mass spectrometer that results in a spectrum of masses, velocities, momenta, or energies. 

Basically, Newtonian mechanics worked well for problems involving terrestrial and even celestial bodies, providing rational and quantifiable relationships between mass, velocity, acceleration, and force. However, in the realm of optics and electricity, numerous observations seemed to defy Newtonian laws. Phenomena such as diffraction and interference could only be explained if light had both particle and wave properties. Indeed, particles such as electrons and x-rays appeared to have both discrete energy states and momentum, properties similar to those of light. None of the classical, or Newtonian, laws could account for such behavior, and such inadequacies led scientists to search for new concepts in the consideration of the nature of reahty. 

Mass velocity through minimum free area between rows of tubes kg/(m -s) IV(h-ft )... 

Mass flux of A by diffusion with respect to the mean mass velocity kmoP(m -s) or moP(cm -s) lbmol/(fF-h)... 

Leveque s approximation Concentration BL is thin. Assume velocity profile is linear. High mass velocity. Fits liquid data well. 

The effective interfacial area depends on a number of factors, as discussed in a review by Charpentier [C/j m. Eng.J., 11, 161 (1976)]. Among these factors are (1) the shape and size of packing, (2) the packing material (for example, plastic generally gives smaller interfacial areas than either metal or ceramic), (3) the liquid mass velocity, and (4), for smaU-diameter towers, the column diameter. 

The mass velocity G = w/A, where w is the mass flow rate and A is the nozzle exit area, at the nozzle exit is given by... 

The exit Mach number Mo may not exceed unity Mo = 1 corresponds to choked flow sonic conditions may exist only at the pipe exit. The mass velocity G in the charts is the choked mass flux for an isentropic nozzle given by Eq. (6-118). For a pipe of finite length. 

G Mass velocity kg/(s-m") lb/(s-fP) q Volume flow rate mVs ftVs... 

Dp = particle diameter, Df = vessel diameter, (note that D /Df has units of foot per foot in the equation), G = superficial mass velocity, k = fluid thermal conductivity, [L = fluid viscosity, and c = fluid specific heat. Other correlations are those of Leva [Jnd. Eng. Chem., 42, 2498 (1950)] ... 

D, 5 = average drop diameter, ft / = disk radius, ft F = spray mass velocity, lb/(min ft of wetted disk periphery) P/ = hquid density, Ib/fo N = disk speed, r/min p = hquia viscosity, lb/(ft min) a = surface tension, Ib/min"... 

Solution. By assuming that the mass-transfer coefficient varies as the 0.8 power of the local gas mass velocity, we can derive the following relation ... 

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