Pressure gradient, impact

To evaluate the impact of intraparticle convection it is necessary to impose a pressure gradient across the network. Such pressure gradients arise naturally in fixed-bed operation, though the pressure difference across a particle is usually only about I cm H O. By solving the Hagen-Poisenille equation across every pore in the network, the overall flow through the particle (network) is known. 

Tlie use of the term "membrane for these filters is somewhat misleading. Membranes are normally used to separate the components of a gas mixture which have different permeabilities through the membrane material. The permeabilities. In turn, can be related to the solubilities and diffusion coefficients in the membrane which differ for different gases. However, for a membrane filter, the gas passes through the pores of the film by a macroscopic flow process, driven by the pressure gradient. No gas separation takes place. The principal mechani.sms of panicle deposition for both fibrous and membrane filters are the dilTusion and impaction of particles of finite diameter. Settling and electro.siaiic effects may contribute to removal. 

This effect is more pronounced for the dense membranes. For porous membranes, at the very high permeation/reaction rate ratios, the conversion decreases for the higher sweep ratios, since the positive effect of increasing the transmembrane pressure gradient is counterbalanced by the negative impacts of enhanced reactant losses. 

The impact of volume fraction in laminar flow of water and ethylene glycol with CuO nanoparticles on the microchannel pressure gradient, temperature profile, and Nusselt number was analyzed. Based on their experimentally validated results, the following was recommended use of high Prandtl number carrier fluids, high aspect ratio channels, high thermal conductivity nanoparticles, and treatment of channel surface to avoid nanoparticle accumulation. 

Another feature of tumors that can have a major impact on the distribution of targeted radiotherapeutics is tumor interstitial fluid pressure. Interstitial fluid pressure results in a pressure gradient that can inhibit the delivery of molecules from the plasma to the extracellular fluid in central regions of a tumor. Tliis pressure gradient is not present in normal tissues because they have a lymphatic system however, tumors do not, creating an additional barrier that must be overcome. Experimental evidence of an elevated interstitial pressure in murine tumor models has been reported by Boucher et al. (1990). As expected, the effect was most apparent at the tumor periphery. Using a mathematical model, the magnitude of this outward convection fluid flow was predicted to be 0.1-0.2 pm/s (Jain and Baxter 1988). 

Fluid permeation. Fluid permeation can be investigated by a classical stationary or a dynamic technique. It provides an effective pore diameter that is the result of the size distribution and the connectivity of the pores the latter can be expressed in term of the tortuosity t which is the ratio of the path that the fluid actually takes and the width over which the pressure gradient is applied (usually the sample thickness). If viscous flow rather than molecular diffusion is the dominant mechanism the weight of the pore size distribution with respect to its impact on the fluid permeation transport is shifted to the large pores. 

Pressure gradients are neglected. Typically, pressure diflerences in MCFCs are in the order of a few millibars, so the pressure distribution does not have a significant impact on the cell performance. If necessary, the pressure drop can be... 

Changes in gas composition and other conditions have different impact on reduction rate of catalysts with different structures. When H2 content is increased, the exchange intensity of the diffusion in pores is increased. When a molecule moves, every component in the mixed gas independently diffuses in the speed of inverse square root proportion to the molecular weight. Therefore, under the same conditions, diffusion of H2 molecules in gas mixture (H2 and H2O) in the pores is faster than the diffusion of gaseous H2O in the opposite direction. As the result, the absolute pressure in pore rises continuously until the partial pressure gradient of H2 and H2O reaches the value of /Mh o/Mh = 300%). The diffusion equations for the two gas flows (H2 and H2O) can be established at this time, while the diffusion gradient in the pores is determined by the slowest step i.e., the diffusion of product H2O. 

Figure 12.16 Impact of pressure gradient (dP/dZ) on metering section volumetric output (0) as a function of metering depth.

The formation of the turbulent twirled stream essentially differs from the forward. Under the influence of a centrifugal force in the twirled stream, there are pressure gradient on radius, the return currents, the raised speeds at a wall, non-linearity of a profile of tangential stresses, etc. In turn, these phenomena make strong impact on regularity of motion of drops of a liquid in a deduster and character of a current in a boundary layer on a phase boundary gas—a liquid, i.e., define both separation efficiency, and a water resistance, and a criticality of work of dedusters [1-9],... 

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