Investigations On The Performance Of A Duct-type Electrostatic Air Cleaner

The contradiction between the successive deterioration of environment and the improvement of people's requirement of indoor air quality make people select a certain type of air-cleaning equipment. Duct-type electrostatic air cleaners (EACs) have more and more wide application in the future because of its low resistance and relatively high collection efficiency. The previous studies indicated that the performance of a EAC would be affected by the geometric parameters and electrical characteristics of it. In the present paper, the effects of the main geometric and operational parameters on the performance of duct-type electrostatic air cleaners were evaluated by integrated experimental study and theoretical analysis.Two models of electrostatic air cleaners were investigated under different flow velocities of the channels, the polarities of applied voltages, wire-wire distance, wire-plate spacing and discharge wire radius. A two-dimensional theoretical model was introduced to predict the collection efficiency of wire-plate and plate-plate type cleaners with the consideration of the analysis of the results. The particle convective diffusion equations under turbulent flow conditions were solved by using numerical methods, and the validation of the model was compared with the results in the literature. Then it was used to evaluate the effects of the prime parameters on the collection efficiency of the EACs, the geometric configuration, average electric field strength (E_av) in the collecting channel, average current density at the plate (j) and the corona power ratio (P/Q) were taken into account, respectively, and some suggestions on the design and improvement of EACs were put into recommendation.The results of the experiments and the numerical simulations show that geometrical parameters have different effects on the performance of EACs. This paper indicated that we should insure the rather broad voltage range firstly and take the back corona and energy consumption into account secondly in the phase of selecting of the discharge wire radius. The wire-wire distance of the single-stagecleaner had better be two times of wire-plate spacing, one discharge wire might as well be set up in one channel of the double-stage cleaner. In principle, longer collecting plates would have more advantages for the increase of collection efficiency of the two types of EACs, but the simulation results show that it is sufficient for single-stage cleaner with the critical length of 12b~14b and for double-stage cleaner with the critical length of 10b from the point of view of economical consideration. Besides, when the length of plate, the radius of corona wire, wire-plate spacing and voltage of the double-stage cleaner are equal to the respective parameters of the single-stage cleaner, the performance of the former is distinctly superior to the latter, whereas the quantity of plate and the weight of the double-stage cleaner would be increased. Therefore, the geometrical configurations and the other main parameters that would affect the performance of the electrostatic cleaners should be considered integrally and practically.