Packed duct flow

Example 4.6 Entropy production in a packed duct flow Fluid flow and the wall-to-fluid heat transfer in a packed duct are of interest in fixed bed chemical reactors, packed separation columns, heat exchangers, and some heat storage systems. In this analysis, we take into account the wall effect on the velocity profile in the calculation of entropy production in a packed duct with the top wall heated and the bottom wall cooled (Figure 4.7). We assume... 

Example 4.5 Entropy production in a packed duct flow with asymmetric heat effects... 

Forced convection heat transfer is probably the most common mode in the process industries. Forced flows may be internal or external. This subsection briefly introduces correlations for estimating heat-transfer coefficients for flows in tubes and ducts flows across plates, cylinders, and spheres flows through tube banks and packed beds heat transfer to nonevaporating falling films and rotating surfaces. Section 11 introduces several types of heat exchangers, design procedures, overall heat-transfer coefficients, and mean temperature differences. 

Sampling of materials consisting of more than one phase at the sampling point is particularly difficult. Common examples are the sampling of liquid or vapour from a plate absorber or distillation column or from a packed column, or the sampling of a multiphase mixture flowing in a pipe or duct. In such cases it is not always known whether the liquid or vapour has been sampled or some combination of both. 

Figure 6. Visualization of mass transfer in monolith structures (flow from left to right). Top Corrugated packing bottom Square duct monolith [9],...

Sprensen, J. P., and W. E. Stewart, Computation of forced convection in slow flow through ducts and packed beds — IV. Convective boundary layers in cubic arrays of spheres, Chem. Eng. Sci., 29, 833-837 (1974). 

Previously it was indicated that for noncircular conduits Fig, 6.10 (the friction factor plot) could be used if we replaced the diameter in both the friction factor and the Reynolds number with 4 times the hydraulic radius (HR). The hydraulic radius is the cross-sectional area perpendicular to flow, divided by the wetted perimeter. For a uniform duct this is a constant. For a packed bed it varies from point to point. But if we multiply both the cross-sectional area and the perimeter by the length of the bed, it becomes... 

Dew point reading could be good but resin is still wet.) Blower rotation incorrect Air ducts blocked Air flow meter incorrect Desiccant bed contaminated Tightly packed material in hopper Check manufacturer s electrical instructions, and change blower rotation Remove obstruction Disengage line exiting dryer repair if needed Replace desiccant (see Note 3) Increase hopper size or drain hopper and refill... 

When the duct is fully occupied by a fixed bed of material which packs uniformly or of irregular-shaped catalyst particles, flow equations (6.15) and (6.16) are still valid provided the geometry-dependent variables, v and, are relative to the actual dimensions of the channels between the particles in the bed. These channels, however, are of different size and shape and change randomly from point to point within the same bed in any direction, so that they cannot be represented by precise mathematical formulation a semi-empirical approach is the only method available. 

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