Fluid-flow parameters, importance

Rheology. Viscosity and other fluid-flow parameters of emulsions are important, not just for establishing pumping and handling protocols, but because they relate to other emulsion properties, such as size distribution of the dispersed phase, the presence of solids or emulsifiers, and the nature of... 

Oil viscosity is an important parameter required in predicting the fluid flow, both in the reservoir and in surface facilities, since the viscosity is a determinant of the velocity with which the fluid will flow under a given pressure drop. Oil viscosity is significantly greater than that of gas (typically 0.2 to 50 cP compared to 0.01 to 0.05 cP under reservoir conditions). 

The quahtative flow distribution in a manifold can be estimated by examining a streamline plot. Figure 13 shows the streamline plot for the manifold having AR = 4. Note that the same amount of fluid flows between two consecutive streamlines. The area ratio is an important parameter affecting the flow distribution in a manifold, as shown in Figure 14a, which shows the percent flow rate in each channel for three cases. As the area ratio increases, the percent flow rate increases in channels no. 1 and no. 8, whereas the percent flow rate decreases in the middle channels. 

The above considerations give us a technique for estimating the required jet momentum and outlet flow rates. Other important parameters are the heights of the inlet and outlet apertures. The choice of these parameters will not, in general, have a significant effect on the overall fluid flow pattern and the resulting distribution of the contaminant, and these should be chosen to optimize the performance of the inlet and exhaust pumps. 

The pressure drop across the cyclone is an important parameter in the evaluation of cyclone performance. It is a measure of the amount of work that is required to operate the cyclone at given conditions, which is important for operational and economical reasons. The total pressure drop over a cyclone consists of losses at the inlet, outlet and within the cyclone body. The main part of the pressure drop, i.e. about 80%, is considered to be pressure losses inside the cyclone due to the energy dissipation by the viscous stress of the turbulent rotational flow [9], The remaining 20% of the pressure drop are caused by the contraction of the fluid flow at the outlet, expansion at the inlet and by fluid friction on the cyclone wall surface. 

To operate SMB chromatography a lot of parameters (column diameter, column length, total column number and number of columns per section, eluent, feed, raffinate, extract and recycle fluid flow and switch time interval) have to be chosen correctly. Therefore, design and process optimization should be done by computer simulations. It is much more difficult to optimize SMB during nonlinear conditions as compared to linear conditions. In fact, empirical approaches for optimization during overloaded and non-linear conditions are in most cases even impossible [96, 97], Computer-assisted optimization is therefore especially important for chiral separations since these CSPs have in general lower saturation capacities compared to non-chiral columns (see paper III). 

Permeability is a parameter defined to measure the physical influence of a porous structure on fluid flow, and for a CVI process it is an important physical parameter for fibre preforms. Another important parameter for porous structure is the porosity, which is the most important geometrical property. According to Darcy s law, the volumetric flow rate Q of a fluid through a porous medium is proportional to the hydrostatic pressure difference (AP) across the structure (see Figure 2.16), the permeability and the cross-section area, and is also inversely proportional to the length of the structure and the viscosity of the fluid, as given by [26]... 

The fluid flow problem requires the solution of all these equations. The dependent variables are p, p, T and Vi. The governing equations are all coupled together. For instance, the momentum equation contains the density and pressure variables, and the viscosity parameter. These quantities depend on the local temperature. The temperature in turn is governed by the energy equation, which contains the velocity in the advective and dissipation terms. However, not all the terms in the equations have the same importance in determining the flow solution. 

The limiting current density is an important parameter for the analysis of mass transfer controlled electrochemical processes and represents the maximum possible reaction rate for a given bulk reactant concentration and fluid flow pattern. During anodic metal dissolution, a mass transfer limiting current does not exist because the surface concentration of the dissolving ion (e.g., Cu + when the anode is composed of copper metal) increases with increasing current density, eventually leading to salt precipitation that blocks the electrode surface. 

Many important applications of fluid dynamics require that density variations be taken into account. The complete field of compressible fluid flow has become very large, and it covers wide ranges of pressure, temperature, and velocity. Chemical engineering practice involves a relatively small area from this field. For incompressible flow the basic parameter is the Reynolds number, a parameter also important in some apphcations of compressible flow. In compressible flow at ordinary densities and high velocities a more basic parameter is the Mach mnnber. At very low densities, where the mean free path of the molecules is appreciable in comparison with the size of the equipment or solid bodies in contact with the gas, other factors must be considered. This type of flow is not treated in this text. 

Single-phase fluid flow in porous media is a well-studied case in the literature. It is important not only for its application, but the characterization of the porous medium itself is also dependent on the study of a single-phase flow. The parameters normally needed are porosity, areal porosity, tortuosity, and permeability. For flow of a constant viscosity Newtonian fluid in a rigid isotropic porous medium, the volume averaged equations can be reduced to the following the continuity equation,... 

Interstitial fluid pressures in normal tissues are approximately atmospheric or slightly sub-atmospheric, but pressures in tumors can exceed atmospheric by 10 to 30mmHg, increasing as the tumor grows. For 1-cm radius tumors, elevated interstitial pressures create an outward fluid flow of 0.1 fim/s [11]. Tumors experience high interstitial pressures because (i) they lack functional lymphatics, so that normal mechanisms for removal of interstitial fluid are not available, (ii) tumor vessels have increased permeability, and (iii) tumor cell proliferation within a confined volume leads to vascular collapse [12]. In both tissue-isolated and subcutaneous tumors, the interstitial pressure is nearly uniform in the center of the tumor and drops sharply at the tumor periphery [13]. Experimental data agree with mathematical models of pressure distribution within tumors, and indicate that two parameters are important determinants for interstitial pressure the effective vascular pressure, (defined in Section 6.2.1), and the hydraulic conductivity ratio, (also defined in Section 6.2.1) [14]. The pressure at the center of the tumor also increases with increasing tumor mass. 

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