Diffusion in an External Force Field Electrical Precipitation

CONVECTIVE DIFFUSION IN AN EXTERNAL FORCE FIELD ELECTRICAL PRECIPITATION 

With typical pfate spacings of 6 to 15 in. and gas velocities of 3 to 10 ftysec, corresponding to Reynolds numbers of 10 and greater, precipitator flows are turbulent. The instantaneous particle flux in the direction normal lo the collecting plate is 

The migration velocity passes through a minimum corresponding to a particle size in the transition region between diffusion and field charging (Chapter 2, Fig. 6). By differentiating (3.92), we see that the efficiency must also pas.s through a minimum at the same particle 

A Cilscade impactor o Optica] particle caunter + DilTuston batter)  

In practice, it is not possible to make accurate calculations of from first principles because of the complexity of the interaction between the particles and the corona discharge. The mechanical and electrical behavior of the deposited dust layer are also difficult to characterize. Thus theory provides guidelines for precipitator design but In practice, design is based to a great extent on empiricism. 

---