Viscosity of air

Before accepting this solution, the Reynolds number should be checked. At the pipe exit, the temperature is given by Eq. (6-120) since the flow is choked. Thus, T[Pg.651]

Figure 2-45. Absolute viscosity of air. By permission. Standards for Steam Jet Ejectors, 3rd Ed., Heat Exchange Institute, 1956 [54] also. Standards for Steam Jet Vacuum Systems, 4th Ed., 1988 [58].

Two principal types of fabric are adaptable to filter use woven fabrics, which are used in shaker and reverse-flow filters and felts, which are used in reverse-pulse filters. The felts made from synthetic fibers are needle felts (i.e., felted on a needle loom) and are normally reinforced with a woven insert. The physical properties and air permeabilities of some typical woven and felt filter fabrics are presented in Tables 17-6 and 17-7. The air permeability of a filter fabric is defined as the flow rate of air in cubic feet per minute (at 70°F, 1 atm) that will pass through 1 ft2 of clean fabric under an applied differential pressure of Vt in water. The resistance coefficient KF of the clean fabric is defined by the equation in Table 17-6, which may be used to calculate the value of KF from the air permeability. If Ap, is taken as 0.5 in water, t as 0.0181 cP (the viscosity of air at 70°F and 1 atm), and Vj as the air permeability, then //, = 27.8/air permeability. 

Sampling rates for the case of total boundary layer-control can be expected to be nearly independent of temperature, since both the diffusion coefficients in air, and the kinematic viscosity of air are only weak functions of temperature (Shoeib and Harner, 2002). This leaves the air-flow velocity as the major factor that can be responsible for the seasonal differences among sampling rates observed by Ockenden et al. (1998). The absence of large R differences between indoor and outdoor exposures may be indicative of membrane-control, but it may also reflect the efficient damping of high flow velocities by the deployment devices used for SPMD air exposures (Ockenden et al., 2001). 

When the viscosities of air-entrained pastes were measured by the same means, the results shown in Fig. 3.7 were obtained for sodium abietate at 0.05% by weight of cement. It can be seen that the magnitude of the effect due to the presence of the admixture itself is small in relation to the effect of the air it causes to be entrained. 

Kg, gas film coefficient A, surface area of water body 7), diffusion coefficient of compound in air W, wind velocity at 2 m above the mean water surface v, kinematic viscosity of air a, thermal diffusion coefficient of air g, acceleration of gravity thermal expansion coefficient of moist air AP, temperature difference between water surface and 2 m height APv virtual temperature difference between water surface and 2 m height. 

Using the reduced-viscosity chart (Fig. 3.3) and knowledge of the critical properties, develop an approximate temperature-dependent expression for the viscosity of air at atmospheric pressure and in a temperature range 300 [Pg.136]

Example 7.3 Consider a clean house bag filter filled with randomly assembled fibers. The porosity of the filter is 0.97, and the fibers have an effective diameter of 10 pm. The length of the filter is 0.1 m. If the flow velocity of the dust-laden air is 0.2 m/s, estimate the pressure drop across the filter. The viscosity of air is 1.8 x 10-5 kg/m s. 

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