Surface area, effect turbulent

This process is similar to the activated sludge process however, it requires a large surface area to cause more temperature effects than that experience in the activated sludge process. The aeration process in this system supplies oxygen to the influent wastewater and the turbulent generated keeps the contents of the basin in suspension. The suspended solids are then removed in a settling tank where the wastewater may further be treated before discharge.23... 

Enhanced chemical reactivity of solid surfaces are associated with these processes. The cavitational erosion generates unpassivated, highly reactive surfaces it causes short-lived high temperatures and pressures at the surface it produces surface defects and deformations it forms fines and increases the surface area of friable solid supports and it ejects material in unknown form into solution. Finally, the local turbulent flow associated with acoustic streaming improves mass transport between the liquid phase and the surface, thus increasing observed reaction rates. In general, all of these effects are likely to be occurring simultaneously. 

What characterises the different incubation steps is the time required to reach thermodynamic equilibrium between an antibody and an antigen in the standard format of microtitre plates. In fact the volume used in each of the incubation steps has been fixed between 100 and 200 pL to be in contact with a surface area of approx. 1 cm2 where the affinity partner is immobilised. The dimensions of the wells are such that the travel of the molecule from the bulk solution to the wall (where the affinity partner is immobilised) is in the order of 1 mm. It must be taken into account that the generation of forced convection or even of turbulence in the wells of a microtitre plate is rather difficult due to the intrinsic dimensions of the wells [10]. Indeed, even if some temperature or shaking effects can help the mass transport from the solution to the wall, the main mass transport phenomenon in these dimensions is ensured by diffusion. 

FIGURE I IA.2 Predicted equilibrium bubble size distribution at three values of turbulent energy dissipation rates. Effect of energy dissipation rate on (a) group mass fraction and (b) total surface area. 

Cell Size Effect. - The mass transfer coefficient is inversely proportional to width of a cell for fully developed laminar region, and surface area is proportional to cell width. This means conversion through a cell is constant. However, as flow is proportional to the square of cell width as velocity is held constant, the conversion efficiency decreases as cell width increases. This tendency is shown in Figure 10. A large cell size may offer a moderate conversion rate and a longer hydrodynamic entrance region. These are favorable characteristics for a catalyst. On the other hand, for fully developed turbulent flow, the mass transfer coefficient increases with cell width to the 0.2 power, and the surface area is proportional to the width. This means conversion increases as the cell width increases to the 0.8 power. Therefore, the cell size effect for turbulent flow is rather small compared with laminar flow. However, the conversion efficiency decreases as cell width increases as is for laminar flow. 

---