Loss coefficient

Fig. 7. (a) Configuration for flow turning. The frictional resistance resulting from the bend length must be added (b) pressure—loss coefficient, K, for 90°... 

For a trumpet-shaped rounded entrance, with a radius of rounding greater than about 15 percent of the pipe diameter (Fig. 6-13Z ), the turbulent flow loss coefficient K is only about 0.1 (Vennard and Street, Elementary Fluid Meehanies, 5th ed., Wiley, New York, 1975, pp. 420-421). Rounding of the inlet prevents formation of the vena eontraeta, thereby reducing the resistance to flow. 

Miller Internal Flow Systems, 2d ed.. Chap. 13, BHRA, Cranfield, 1990) gives the most complete information on losses in bends and curved pipes. For turbulent flow in circular cross-seclion bends of constant area, as shown in Fig. 6-14 7, a more accurate estimate of the loss coefficient K than that given in Table 6-4 is... 

FIG. 6-14 Loss coefficients for flow in hends and curved pipes (a) flow geometry, (h) loss coefficient for a smooth-waUed hend at Re = 10, (c) Re correction factor, (d) outlet pipe correction factor (From D S. Millet] Internal Flow Systems, 2d. ed., BHRA, Cranfield, V.K., 1990.)... 

Benson, R.S., A Review of Methods for Assessing Loss Coefficients in Radial Gas Turbines, International Journal of Mechanical Sciences, 12 (1970), pp. 905-932. 

Brown, L.E., Axial Flow Compressor and Turbine Loss Coefficients A Comparison of Several Parameters, Journal of Engineering for Power, ASME Transactions 94A, pp. 193-201, 1972. 

Liner holes. Liner area to casing area and liner hold area to casing area are important to the performance of combustors. For example, the pressure loss coefficient has a minimum value in the range of 0.6 of the liner area/ casing area ratio with a temperature ratio of 4 1. 

A circular plate of diameter 0.5 m is to be moulded using a sprue gate in its centre. If the melt pressure is 50 MN/m and the pressure loss coefficient is 0.6 estimate the clamping force required. 

The container shown at the top of p. 341 is injection moulded using a gate at point A. If the injection pressure at the nozzle is 140 MN/m and the pressure loss coefficient, m, is 0.5, estimate (i) the flow ratio and (ii) the clamping force needed. 

The minor loss coefficient depends on the Reynolds number because this dependency is weak, it is normally ignored. The minor loss coefficients for different resistances are given in textbooks. 

TABLE 10.7 Heat Loss Coefficients (h by Natural Convection ... 

Equation (14.91) contains only the mass flow ratio /u as a characteristic number of the mechanics of similitude of the mixture. All the other irnpor rant factors, such as particle size, solid density, etc., are contained in the additional pressure-loss coefficient of the solid particles, A, which is determined separately for each material. 

But how can we estimate the pressure-loss coefficient A Stegmaier - has summarized horizontal transport for several fine-granular solids by a correla tion which contains some characteristics of the material. The same idea has been used by Weber, who has found a correlation of the pressure-loss coefficient for vertical pneumatic conveyance based on data measured by Flatow. In order to express these models, we first introduce two dimensiitnless numbers... 

It is known from experience with vertical pneumatic transport that the influence of weight prevails at low velocities, but as the velocity increases friction gains importance. Therefore, in the calculation of the pressure loss one must find not only the weight of the solids, which could be set up theoretically, but also an empirical relationship for vertical transport from the measured data. A correlation of the pressure-loss coefficient for vertical pneumatic conveyance according to data measured by Flatow " has been developed by Weber, and the result is... 

FIGURE M.I3 Pressure-loss coefficient for horizontal transport according to Stegmaier. ... 

FIGURE 14.14 Correiabon of the pressure loss coefficient for vetnca pneumatic conveyance based on Flatow s data according to Weber. ... 

In this chapter the pressure drop for pneumatic conveying pipe flow is studied. The conventional calculation method is based on the use of an additional pressure loss coefficient of the solid particles. The advantage of this classical method is that in principle it can be applied to any type of pneumatic flow. On the other hand, its great disadvantage is that the additional pressure loss coefficient is a complicated function of the density and the velocity of the conveying gas. z lso, it is difficult to illustrate the additional pressure loss coefficient and this makes the theoretical study of it troublesome. 

The new pressure loss equation presented here is based on determining two parameters the velocity difference between gas and conveyed material and the falling velocity of the material. The advantage of this method is that no additional pressure loss coefficient is needed. The two parameters are physically clear and they are quite easily modeled for different cases by theoretical considerations, which makes the method reliable and applicable to various ap>-plications. The new calculation method presented here can be applied to cases where solids are conveyed in an apparently uniform suspension in a so-called lean or dilute-phase flow. 

Discharge or entry loss of a louver The reduction in airflow caused by a louver. The discharge loss coefficient is equal to the actual airflow rate divided by the theoretical airflow rate at given pressure difference across the louver. If tested with the airflow in the reverse direction, the coefficient becomes the entry loss coefficient. 

In addition to the irreversibilities associated with these components, pressure losses (Ap) may occur in various parts of the plant (e.g. in the entry and exit ducting, the combustion chamber, and the heat exchanger). These are usually expressed in terms of non-dimensional pressure loss coefficients, Ap/(p) N, where (/ )in is the pressure at entry to the duct. (Mach numbers are assumed to be low, with static and stagnation pressures and their loss coefficients approximately the same.)... 

Calculation of the specific work and the arbitrary overall efficiency may now be made parallel to the method used for the a/s cycle. The maximum and minimum temperatures are specified, together with compressor and turbine efficiencies. A compressor pressure ratio (r) is selected, and with the pressure loss coefficients specified, the corresponding turbine pressure ratio is obtained. With the compressor exit temperature T2 known and Tt, specified, the temperature change in combustion is also known, and the fuel-air ratio / may then be obtained. Approximate mean values of specific heats are then obtained from Fig. 3.12. Either they may be employed directly, or n and n may be obtained and used. 

Note that a somewhat more accurate result may be obtained by following the detailed loss coefficients given in Figures 2-12 through 2-16. However, most preliminary engineering design calculations for this type of water system do not warrant the extra detail. 

Cvw eddy loss coefficient, dimensionless. Table 8-22 K<. = loss coefficient, valves closed (sec) (in.)/ft, see Table 8-23... 

Closed and Open Loss Coefficients for Dry Tray Pressure Drop Equations 8-314 and 8-315... 

Capacity factor based on tower area, ft/sec Capacity fector at flood, ft/sec Liquid gradient vapor load correction factor or Discharge coefficient (see accompanying table) or Gas phase loading factor, ft/sec. Equation 8-281 Eddy loss coefficient, dimensionless. Table 8-22 Wet cap pressure drop correction factor. Figure 8-115... 

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