Pressure drop curve

Figure 4-21. Typical wire mesh mist eliminator pressure drop curves for one style of mesh at three different liquid loadings. Others follow similar pressure drop patterns. By permission, Otto H. York Co., Inc.

For Figure 9-21A the loading region is centered about the 0.75 in/ft pressure drop curve the preferred design range being 0.35 to a maximum of 1.0 in. of water/ft. 

Figure 9-21F is the most current updated version of the GPDC as presented by Strigle [139] to facilitate interpolation of the ordinate and pressure drop curves on the chart. The flooding and loading regions are not identified. For this chart ... 

Strigle [82] and Kister [93] point out the importance of evaluating data where available to reduce the need for interpolating the GPDC charts. The question of reasonably accurate ( 10 to 15%) flooding pressure drop data has been studied by Kister [93], and the results suggest that the establishment of flooding pressure drop curves... 

As a comparison or alternate procedure, the pressure drop at the flooding point as indicated by the upper break in the pressure drop curve can be estimated from Table 9-33 and Figure 9-34D for rings and saddles [81]. The values in the table multiplied by the correction ratio gives the pressure drop for the liquid in question, expressed as inches of water. 

Values of B, C and Sp are given in Table 9-50. Pressure drop values, AP /N, per individual deck range from 0.003-0.006 in. water for low L and Ga rates to 0.03-0.06 in. water for high L (3,500) and Ga (2,000) rates [19]. Values of Ge are taken from Figure 9-119. Typical pressure drop curve is shown in Figure 9-120. 

The gas pressure drop is a function of the gas and liquid flow rates and the size and type of packing. It relates to the overall cost of the air stripper and to its performance. The gas pressure drop through a stripping unit can be determined from the pressure drop curve. 

Figure 2 Typical pressure drop curve as a function of gas velocity. Source Adapted from Ref. 19.

Fig. 4 illustrates the two previously discussed pressure drops across the 35-mm (1.4-in.] hydrocyclone. The reject curve is based on a reject ratio of -1 %. A family of reject-pressure-drop curves can be generated for a range of reject ratios. Fig 5 illustrates a family of reject curves ranging from 0 to 3% for the 60-mm (2.4-in.] cyclones used on the Hutton TLP. 

Equation (14-142) permits finding the pressure drop curve in Fig. 14-55 or 14-56 at which incipient flooding occurs. 

For low-capacity random packings, such as the small first-generation packings and those smaller than 1-in diameter (Fp > 60 ft-1), calculated flood pressure drops are well in excess of the upper pressure drop curve in Fig. 14-55. For these packings only, the original Eckert flood correlation Chem. Eng. Prog. 66(3), 39 (1970)] found in pre-1997 editions of this handbook and other major distillation texts is suitable. 

A transparent PEM fuel cell with a single straight channel was designed by Ma et al.11 to study liquid water transport in the cathode channel (this study is also mentioned in Section 2.5). The pressure drop between the inlet and outlet of the channel on the cathode side was used as a diagnostic signal to monitor liquid water accumulation and removal. The proper gas velocities for different currents were determined according to the pressure drop curves. 

The constraint of the pressure drop across the downcomer is graphically illustrated in Fig. 10.8. For a given solids inventory in the downcomer and given gas and solids flow rates, the pressures at the bottom of the riser and the downcomer can be determined at steady state. Under normal operating conditions (point A in the figure), the pressure drop across the riser is balanced by the pressure drop across the recirculation loop. If a small reduction in gas velocity takes place, the flow in the riser responds by moving upward along the pressure drop curve of the riser to point B. On point B of line AB, the decrease in the gas velocity causes the pressure drop across the riser to rise by SPt, which has to be balanced by the... 

As liquid rates are raised, the liquid occupies some of the cross-section area, making the openings for gas flow smaller. The pressure drop curve will parallel A-B but will be somewhat above it. At high liquid flow rates, the packing voids fill up with frothy liquid. A portion of the energy of the gas is used to support the liquid in the column and pressure drop becomes proportional to the gas rate raised to a power different (usually lower) than 2 (region A -B ). The point where the packing voids fill up, i.e., when tower operation switches from vapor-continuous (normal) to liquid continuous is termed phase inversion. 

The tumdoum maldistribution regime (region to the left of A in Fig, 8.16a, not identified from the pressure drop curves) Operation in this region is undesirable because of poor efficiency. 

For each packing, sketch an empirical curve such that (a) its upper end passes through the point Fsf, APF with a slope approaching infinity, and (b) its lower end becomes tangent to the straight, wet-pressure-drop line at an abscissa value of Fsf/2. These two pressure-drop curves for the loading regions are shown by the dashed lines of Fig. 11.1. 

Determine the pressure drops from the curves. The overall pressure-drop curve for each packing consists of the solid curve at low gas loadings and the dashed curve at loadings between the... 

Fig. 8. Pressure drop curves for fluidization in conical and conical-cylindrical vessels (Gelperin et at, Gl).

Figure 17 Characteristic performance curve (upper) and pressure drop curve (lower) for OCFS in distillation and catalytic distillation service, as function of throughput capacity.

Air-stripping tower diameter is selected as a function of the liquid loading rates necessitated by the required design flow capability. The optimum tower diameter may be determined with the use of pressure-drop curves developed by Eckert (11) as shown in Fig. 3. The volumetric air-to-water ratio, calculated by Eq. (9), is converted to a weight-to-weight ratio and plotted on the abscissa in the form ... 

The ordinate value, corresponding to the intersection of the abscissa value with the appropriate pressure-drop curve (as supplied by the packing manufacturer), allows the determination of the allowable gas-flow rate from... 

Typically, the air-stripper manufacturer will supply liquid flow ranges acceptable for a particular tower. Selecting an air stripper for which the design flow is at the lower end of the tower s rated capacity will produce high contaminant removal rates, but may not optimize power requirements. For large-scale systems where significant operational costs may be incurred by overdesigning the system, the use of pressure-drop curves and calculations such as Eqs. (1)-(13) are required. 

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