Evaluation of field-diffusion charging models for airborne suspended particles charged by corona ions: Sum of charge quantities and sum of charging rates

To evaluate the field-diffusion charging models, a comparative study is conducted in a systematic way in this paper. A field-diffusion charge quantity sum model (FDCQSM) and a field-diffusion charging rate sum model (FDCRSM) in which the Maxwell-Wagner relaxation model for unipolar field charging is proposed to extend to bipolar charging. The predictions of the two models are compared with the experimental results reported in the literature over wide ranges of particle diameters and electric fields. The results show that the FDCQSM is in good consistence with experiments, while the FDCRSM performs well only if either diffusion charging or field charging dominates. Moreover, the physical meaning of the FDCRSM, the effects of ion property and particle's conductivity on the particle charge, and applicability of the FDCQSM are discussed. The outcome that the FDCRSM works badly when field charging and diffusion charging are important indicates that it is likely as empirical as the FDCQSM. And FDCQSM seems to be valid in the study of the effects of aerosols on the electrical environment around high voltage direct current (HVDC) transmission lines, while the FDCRSM is not recommended.