Local resistance coefficient

Some of the structural factors, such as the changes in cross section area of flow passage and flow direction etc., may also cause pressure losses. Obviously, these factors depend on the specific structure of the device under consideration and vary from device to device. For convenience, and for more generalization, the resistance resulting from all the structural factors is represented in terms of the combined local resistance coefficient, 1s, which is also related to the velocity of the gas flow in the accelerating tube, i.e., the impinging velocity, utl. i.e.. 

Figure 4.5 Part of the data measured for the local resistance coefficient lcp ( pi)=3.51-6.42 m-s l) — averaged over 490 sets of data + rape seeds, S/d=4.0 Op Ax omillets, Sld=5.0.

The local resistance coefficient IC ) is calculated for a total of 490 sets of measured data, and the results are given in Fig. 4.5. 

As can be seen from the table, the mass flow rate ratio m m, has no effect on -Apim, and the equivalent local resistance coefficient jm calculated with Eq. (4.13) is essentially kept constant. This implies that the pressure drop across the impingement zone is independent of the presence of particles. The value for averaged over a total of 490 sets of data is equal to 0.096. So, the pressure drop across the impingement zone can be calculated with the relationship below ... 

When normal sites in a crystal structure are replaced by impurity atoms, or vacancies, or interstitial atoms, the local electronic structure is disturbed and local electronic states are introduced. Now when a dislocation kink moves into such a site, its energy changes, not by a minute amount but by some significant amount. The resistance to further motion is best described as an increase in the local viscosity coefficient, remembering that plastic deformation is time dependent. A viscosity coefficient, q relates a rate d8/dt with a stress, x ... 

The motion of a spherical particle in a non-local fluid was considered by Pokrovskii and Pyshnograi (1988). We reproduce the calculation of the resistant coefficient here. 

The constant triadic and pseudotriadic in square brackets are intrinsic resistance coefficients. Furthermore, the latter is independent of choice of origin, as can be seen from the fact that neutrally buoyant particle immersed in a shear flow is, in general, unable to follow the local fluid motion. Rather, linear and angular slip must obtain. 

Considering the water beam shrinkage and head loss for local resistance and other factors, the actual flow is less than the ideal flow it need to correction by multiply a flow coefficient C therefore the actual flow is ... 

In weir flow calculation formula, the flow coefficient is relate to the weir flow shrinkage and head loss for local resistance non-uniform velocity coefficient a is relate to the inhomogeneous degree of approach velocity in flume cross section and the ratio of weir head H and weir height P. Therefore, the value or expression of and a are not identical by test in specific conditions and certain circumstances at home and abroad. 

Hydraulic resistance of centrifugal machines is generally viewed as the local resistance. Hydraulic resistance coefficient, pressure losses in the unit determined experimentally and are mainly as a function of the geometry and the Reynolds number [9]. 

In order to improve the cooling effect of the PM motor, the water in the channel of jacket should be turbulent for the high convective heat transfer coefficient. In order to decrease the local resistance of water flow path, the section profile of the channel is designed as semielliptical type. 

The classical approach to analysis of this problem still relies on Eq. (1). Consider the cooling of a solid surface by a fluid. One hypothesizes a stagnant film of the fluid that possesses all the fluid-phase resistance to heat transfer. The properties of the fluid and the thickness of the film determine the magnitude of the resistance. Boundary-layer theory enables estimation of various film thicknesses, but normal engineering practice is based on the use of individual coeflflcients that are empirically determined. Thus, the local individual coefficient for the film at a surface is defined by the Newton relation... 

Hydrodynamic resistance to the motion of the dispersed (spherical) particles from the continuum solvent is generally taken into account through a local friction coefficient... 

The coefficient of local resistance to the unit area with sudden expansion is calculated (in the calculation of the velocity head speed in a smaller cross section) by the formula (l-Sj/S (Fig. 13.1), and cylindrical por-... 

FIGURE 13.1 Scheme for calculation of coefficient of local resistance. 

By analogy with flow of water alone it is possible to introduce a coefficient of local resistance also for capsules flow and to define total pressure losses in a bend as the sum of friction losses in the straight pipe, he, and local losses in the bend... 

Hard plating is noted for its excellent hardness, wear resistance, and low coefficient of friction. Decorative plating retains its brilliance because air exposure immediately forms a thin, invisible protective oxide film. The chromium is not appHed directiy to the surface of the base metal but rather over a nickel (see Nickel and nickel alloys) plate, which in turn is laid over a copper (qv) plate. Because the chromium plate is not free of cracks, pores, and similar imperfections, the intermediate nickel layer must provide the basic protection. Indeed, optimum performance is obtained when a controlled but high density (40—80 microcrack intersections per linear millimeter) of microcracks is achieved in the chromium lea ding to reduced local galvanic current density at the imperfections and increased cathode polarization. A duplex nickel layer containing small amounts of sulfur is generally used. In addition to... 

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