Flow properties factors

Selection of Equipment The principal factors which influence mixing-equipment choice are (1) the process requirements, (2) the flow properties of the process fluids, (3) equipment costs, and (4) construction materials required. 

The value of tire heat transfer coefficient of die gas is dependent on die rate of flow of the gas, and on whether the gas is in streamline or turbulent flow. This factor depends on the flow rate of tire gas and on physical properties of the gas, namely the density and viscosity. In the application of models of chemical reactors in which gas-solid reactions are caiTied out, it is useful to define a dimensionless number criterion which can be used to determine the state of flow of the gas no matter what the physical dimensions of the reactor and its solid content. Such a criterion which is used is the Reynolds number of the gas. For example, the characteristic length in tire definition of this number when a gas is flowing along a mbe is the diameter of the tube. The value of the Reynolds number when the gas is in streamline, or linear flow, is less than about 2000, and above this number the gas is in mrbulent flow. For the flow... 

Antioxidants may be assessed in a variety of ways. For screening and for fundamental studies the induction period and rate of oxidation of petroleum fractions with and without antioxidants present provide useful model systems. Since the effect of oxidation differs from polymer to polymer it is important to evaluate the efficacy of the antioxidant with respect to some property seriously affected by oxidation. Thus for polyethylene it is common to study changes in flow properties and in power factor in polypropylene, flow properties and tendency to embrittlement in natural rubber vulcanisates, changes in tensile strength and tear strength. 

J.2 Effects of environmental and molecular factors on viscous flow properties... 

Figure 10-47. Flow inside tubes for gas and vapors. Physical property factor depends on viscosity, specific heat, and thermal conductivity. (Used by permission Ning Hsing Chen, Chemical Engineering, V. 66, No. 1, 1959. McGraw-Hill, Inc. All rights reserved.)...

Factors affecting the mix of active ingredients and excipients should be discussed. These should include particle size and shape, rugosity, charge, flow properties, and water content. Since the dose delivery for these products is dependent on air flow characteristics, an attempt should be made to establish an in vivo-in vitro correlation. 

This equation defines the permeability (K) and is known as Darcy s law. The most common unit for the permeability is the darcy, which is defined as the flow rate in cm3/s that results when a pressure drop of 1 atm is applied to a porous medium that is 1 cm2 in cross-sectional area and 1 cm long, for a fluid with viscosity of 1 cP. It should be evident that the dimensions of the darcy are L2, and the conversion factors are (approximately) 10 x cm2/darcy C5 10-11 ft2/darcy. The flow properties of tight, crude oil bearing, rock formations are often described in permeability units of millidarcies. 

The rheological properties of a suspension depend upon factors such as the size, shape and concentration of the particles, the stability of the suspension and the viscosity of the medium. Flow properties can be modified by altering the surface charge... 

In pHPLC, there are numerous types of columns used. The comparison and characterization of these columns are often discussed in terms of thermodynamic properties and kinetic characteristics. The retention factor, k, selectivity, a, and the peak asymmetry are believed to be representative parameters for the thermodynamic properties, while the kinetic characteristics are often expressed in dimensionless magnitudes of reduced plate height, h, separation impedance, E, and flow resistance factor, ( ). 3... 

Fig. 2.5. Steady-state and dynamic oscillatory flow measurements on a 2 wt. per cent solution of polystyrene S 111 in Aroclor 1248 according to Philippoff (57). ( ) steady shear viscosity (a) dynamic viscosity tj, ( ) cot 1% from flow birefringence, (A) cot <5 from dynamic measurements, all at 25° C. (o) cot 8 from dynamic measurements at 5° C. Steady-state flow properties as functions of shear rate q, dynamic properties as functions of angular frequency m. Shift factor aT which is equal to unity for 25° C, is explained in the text, cot 2 % and cot 8 are expressed in terms of shear (see eqs. 2.11 and 2.22)...

Complexity in multiphase processes arises predominantly from the coupling of chemical reaction rates to mass transfer rates. Only in special circumstances does the overall reaction rate bear a simple relationship to the limiting chemical reaction rate. Thus, for studies of the chemical reaction mechanism, for which true chemical rates are required allied to known reactant concentrations at the reaction site, the study technique must properly differentiate the mass transfer and chemical reaction components of the overall rate. The coupling can be influenced by several physical factors, and may differently affect the desired process and undesired competing processes. Process selectivities, which are determined by relative chemical reaction rates (see Chapter 2), can thenbe modulated by the physical characteristics of the reaction system. These physical characteristics can be equilibrium related, in particular to reactant and product solubilities or distribution coefficients, or maybe related to the mass transfer properties imposed on the reaction by the flow properties of the system. 

In general, in the academic literature on Colloid Science, the latter states are regarded as an end-product and the main emphasis in research has been directed towards understanding the factors which control stability. However, in the technological application of latices, it is often material in the flocculated state which is utilised in order to obtain the desired flow properties. In fact, in order to focus attention on the question of floe structure and pursue this topic further, we must ask a series of questions -... 

Using IT lb/h, for fluid flow allows usage of this same equation for gas or liquid the density term p also applies to either. The velocity variable and density transport property factor must stay reasonably near a constant value for the Darcy equation to be valid. For a liquid fluid, p and v remain nearly constant. Thus, most any pipeline length may be calculated using a single application of Eq. (6.6). 

It is essential to characterize formulation flow properties—and the factors which impact on it (Table 7.8)—at the beginning of the formulation design and optimization stages. Several different methods are available for determining the flow properties of powder mixtures that can serve as tools for prototype formulation screening 55... 

Factors Affecting Material Flow. Although material flow is a function of its cohesive properties, factors known to affect material flowability include moisture content, temperature, particle size, and time of storage at rest. Therefore, the flow properties of material should be measured to determine the effects of the environmental conditions discussed below. 

The presence of inerts can override chemical factors within pitches undergoing pyrolysis. In fact, Marsh et al. (110) postulate that the chemistry of polymerization within mesophase may be dependent upon the flow properties of the mesophase. Hence, inerts may influence pyrolysis chemistry because they can restrict movement of mesophase. 

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