Pressure drop number

The incremental pressure drop number K(x) in the hydrodynamic entrance region is expressed as... 

The relationship between the friction factor, axial pressure drop, and incremental pressure drop number is the following ... 

Solutions for the Flow with Re < 400. It has been found that the effects of axial momentum diffusion and radial pressure variation are significant only in the duct inlet of x < 0.005. Chen [11] obtained the dimensionless hydrodynamic entrance length L y and the fully developed incremental pressure drop number K(< >), which are given by... 

The fully developed incremental pressure drop number K(°°) for elliptic ducts has been found to be independent of the duct aspect ratio a = 2bl2a [187]. The value of (< >) is recommended to be 1.26 for practical calculations [2]. 

Hydrodynamically Developing Flow. Bhatti [181] has analyzed hydrodynamically developing flow in elliptic ducts. The apparent friction factors and incremental pressure drop numbers can be expressed as ... 

TABLE 5.55 Fully Developed Friction Factors, Incremental Pressure Drop Numbers, and Nusselt Numbers for Some Quadrilateral Ducts [278]... 

Simultaneously developing flow in annular sector ducts for air (Pr = 0.7) has been analyzed by Renzoni and Prakash [287]. In their analysis, the outer curved wall is treated as adiabatic, and the boundary condition is imposed on the inner curved wall as well as on the two straight walls of the sector. The fully developed friction factors, incremental pressure drop numbers, hydrodynamic entrance lengths, and thermal entrance lengths are presented in Table 5.62. The term L y used in Table 5.62 is defined as the dimensionless axial distance at which /app Re = 1.05/ Re. The fully developed Nusselt numbers are represented by Nu/< in order not to confuse the reader since the thermal boundary condition applied in Renzoni and Prakash [287] is different from those defined in the section. 

K(o°) Incremental pressure drop number for fully developed flow, see Eq. 17.86 for definition, dimensionless... 

This equation allows the evaluation of the hydrodynamic length if (me knows, for the considered cross section, the value of the fuUy developed Poiseuille number (/Refd), the fuUy developed ratio between the maximum and the mean value of the velocity, and K(po), the asymptotic incremental pressure drop number ... 

Sometimes, the pressure drop in the hydrodynamic entrance region is calculated by introducing the incremental pressure drop number K z) this term takes into account the additional pressure drop due to momentum change and the accumulated increment in wall shear between developing flow and developed flow. By introducing K z), the total pressure drop is calculated as follows ... 

By combining Eqs. 13 and 14, the relation between the apparent Fanning friction factor and the incremental pressure drop number can be written as follows ... 

Elution volume, exclusion chromatography Flow rate, column Gas/liquid volume ratio Inner column volume Interstitial (outer) volume Kovats retention indices Matrix volume Net retention volume Obstruction factor Packing uniformity factor Particle diameter Partition coefficient Partition ratio Peak asymmetry factor Peak resolution Plate height Plate number Porosity, column Pressure, column inlet Presure, column outlet Pressure drop... 

Fig. 23. Pressure drop and flooding correlation for various random packings (95). ip = p- o IP-l (standard acceleration of free fall) = 9.81 m/s, p, = liquid viscosity ia mPa-s numbers on lines represent pressure drop, mm H2O /m of packed height to convert to ia. H2O /ft multiply by 0.012. Packing...

Pressure Drop. The prediction of pressure drop in fixed beds of adsorbent particles is important. When the pressure loss is too high, cosdy compression may be increased, adsorbent may be fluidized and subject to attrition, or the excessive force may cmsh the particles. As discussed previously, RPSA rehes on pressure drop for separation. Because of the cychc nature of adsorption processes, pressure drop must be calculated for each of the steps of the cycle. The most commonly used pressure drop equations for fixed beds of adsorbent are those of Ergun (143), Leva (144), and Brownell and co-workers (145). Each of these correlations uses a particle Reynolds number (Re = G///) and friction factor (f) to calculate the pressure drop (AP) per... 

La.mina.r Flow Elements. Each of the previously discussed differential-pressure meters exhibits a square root relationship between differential pressure and flow there is one type that does not. Laminar flow meters use a series of capillary tubes, roUed metal, or sintered elements to divide the flow conduit into innumerable small passages. These passages are made small enough that the Reynolds number in each is kept below 2000 for all operating conditions. Under these conditions, the pressure drop is a measure of the viscous drag and is linear with flow rate as shown by the PoiseuiHe equation for capilary flow ... 

Design Considerations. For a perforated plate, the pressure drop across the distributor should be at least 30% of the bed pressure drop when operating at the lowest expected gas velocity. The number of holes in the distributor should exceed 10 per square meter. The pressure drop, AP, across the distributor is given by... 

The pressure drop accompanying pipe flow of such fluids can be described in terms of a generalized Reynolds number, which for pseudoplastic or dilatant fluids takes the form ... 

Eurther research on convective transport under low Reynolds number, quasicontinuum conditions is needed before the optimal design of such a micro heat exchanger is possible. The cooling heat exchanger is usually thermally linked to a relatively massive substrate. The effects of this linkage need to be explored and accurate methods of predicting the heat-transfer and pressure-drop performance need to be developed. 

For pressure drop inside tubes, d is 0.046 and F is the fluid-flow path length. Across tubes banks, a is 0.75 and F is the product of the number of tube rows and the number of fluid passes across the tube bank. The physical property term is again tabulated after being normalised so that the lowest value is approximately unity. 

---