Pressure drop calculating the

For estimating purposes in usual piping systems, the values of pressure drop across an orifice or nozzle will range from 2 to 5 psi. For more exact system pressure drop calculations, the loss across these devices should be calculated using some size assumptions. 

Recommendations The reader should consult Refs. 11 and 45 for the pressure drop calculations. The Hutton and Leung model should be verified with additional experimental data obtained with small particles and hydrocarbon systems. 

In measuring the flow of fluids in a pipeline, a differential manometer, as shown in Fig. El.26, can be used to determine the pressure difference across an orifice plate. The flow rate can be calibrated with the observed pressure drop. Calculate the pressure drop p — pi in pascal. 

Neglecting pressure drop, calculate the catalyst weight necessary to achieve 80 r conversion of ooctane in a CSTR and in a plug-flow reactor. If pressure drop is taken into account and the l-in. catalyst pellets are packed in ll-in. schedule SO pipes 35 ft lung, what catalyst weight is necessary to achieve SO "/ - conversion The void fraction is 40 and the density of the camlyst is 2.6 g/cm. ... 

TTie loss coefficient (K) of fittings and block valves are function of Reynolds number and the nominal line size (dfl, in inch). The three K (Kl, Ki, and Kd> and equivalent line length (U,) of different fittings and block valves are listed in Table 3. Eq. (30b) is used to calculate control valve K with known inlet line tnside diameter D (in fl), and control valve sizing coefficient (Cv). Control valve pressure drop calculation by this method is a rough estimate, For more accurate control valve pressure drop calculation, the methods in Chapter 7 should be used. 

Roughness of the pipe wall is an important design parameter for pressure drop calculation. The roughness depends on the type of pipe being used. Most commonly used pipe materials have roughnesses as given in Table 2.3. 

For two-phase flow, heat gain/loss is also an important consideration, because this dictates the vapor/liquid fraction of the flow. Apart from changing the overall physical properties, this also changes the flow regime and will have a substantial impact in pressure drop calculation. The heat loss/ gain can be used for compressible fluids for better results however, it is of less importance for multiphase flow, unless the thermodynamic correlations are used to estimate the vapor/liquid fraction of the fluid. 

For direct measurement from core samples, the samples are mounted in a holder and gas is flowed through the core. The pressure drop across the core and the flowrate are measured. Providing the gas viscosity (ji) and sample dimensions are known the permeability can be calculated using the Darcy equation shown below. 

In pipe distributors, the pressure drop requited for good gas distribution is 30% of the bed pressure drop for upward facing holes, but only 10% for downward facing ones. The pressure drop calculation and the recommended hole density are the same as for a perforated plate. To maintain good gas distribution within the header system, it is recommended the relation... 

Total pressure drop for vertical upflow of gases and solids includes acceleration and fric tional affec ts also found in horizontal flow, plus potential energy or hydrostatic effects. Govier and Aziz review many of the pressure drop calculation methods and provide recommendations for their use. See also Yang AIChE J., 24, 548-552 [1978]). 

Example 9 Pipe Distrihator A 3-in schedule 40 (inside diameter 7.793 cm) pipe is to be used as a distributor for a flow of 0.010 mVs of water (p = 1,000 kg/m, i= 0.001 Pa s). The pipe is 0.7 m long and is to have 10 holes of uniform diameter and spacing along the length of the pipe. The distributor pipe is submerged. Calculate the required hole size to limit maldistribution to 5 percent, and estimate the pressure drop across the distributor. 

Frictional Pressure Drop Usually this does not have a significant effect on the reaclor size, except perhaps when the flow is two-phase. Some approximate relations fbe cited that are adequate for pressure-drop calculations of homogeneous flow reactions in pipelines. The pressure drop is given by... 

The simplest continuous-distillation process is the adiabatic single-stage equihbrium-flash process pictured in Fig. 13-25. Feed temperature and the pressure drop across the valve are adjusted to vaporize the feed to the desired extent, while the drum provides disengaging space to allow the vapor to separate from the liquid. The expansion across the valve is at constant enthalpy, and this facd can be used to calculate To (or T to give a desired To). 

Pressure drop across the disperser is calculated by variations of the standard orifice equation ... 

Pressure drop through the aerated hquid [hf in Eq. (14-106)] is calculated by... 

Example 13 Packed Column Pressure Drop Air and water are flowing coiinterciirrently through a bed of 2-inch metal Pali rings. The air mass velocity is 2.03 kg/s-m (1500 Ihs/hr-fd), and the liquid mass velocity is 12.20 kg/s-m (9000 Ihs/hr-fr). Calculate the pressure drop hy the generalized pres-... 

The velocities are suggestive only and are to be used to approximate line size as a starting point for pressure drop calculations. 

Constants C and K can be determined from several measurements of filtrate volumes taken at different time intervals. There are some doubts as to the actual constancy of C and K during constant pressure filtration. Constants C and K depend on r (specific volumetric cake resistance), which, in turn, depends on the pressure drop across the cake. This AP causes some changes in the cake, especially during the initial stages of filtration. When the cake is very thin, the main portion of the total pressure drop is exerted on the filter medium. As the cake becomes thicker, the pressure drop through the cake increases rapidly but then levels off to a constant value. Isobaric filtration shows insignificant deviation from the expressions developed. For approximate calculations, it is possible to neglect the resistance of the filter plate, provided the cake is not too thin. Then the filter plate resistance, Rf, is equal to zero, C = 0, and r = 0. Hence, a simplified equation is = Kr. 

Another important objective which must be considered is to provide adequate cyclone capacity for the application. The volume of feed slurry that a given cyclone can handle is related to the pressure drop across the cyclone. The relationship between flow rate and pressure drop for several different sizes of standard cyclones is shown in Figure 56. As shown, the flow rate increases as the pressure drop increases. In order to utilize this graph, the pressure drop used for calculating the separation is used to determine the flow rate for the cyclone diameter which was... 

Pressure drop calculations for shnple geometries like pipe flows are straightforward. The Farming friction factor is given by ... 

The equivalent length of the main flare header is then calculated from the flare stack to the last safety valve, taking into consideration the straight length of the pipe and approximate equivalent lengths for bends, etc. If the achial location of the flare stack is not known by that time, it maybe assumed to be 500 ft from the last piece of equipment. Later on, even if it varies from 500 ft, it will not affect the pressure drop calculation at all compared with the entire length of the pipe. 

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