%0 Journal Article %T Enhancement of Natural Convection in Circular and Triangular Ducts Using Corona Discharge in Air and Nitrogen %J Scientia Iranica %I Sharif University of Technology %Z 1026-3098 %A Molki, M. %A Harirchian, T. %D 2008 %\ 02/01/2008 %V 15 %N 1 %P - %! Enhancement of Natural Convection in Circular and Triangular Ducts Using Corona Discharge in Air and Nitrogen %R %X A computational e ort is undertaken to investigate the e ect of corona discharge in air and nitrogen gas on the enhancement of heat transfer. A corona is a visible luminous emission that occurs in the vicinity of sharp edges where the electric eld is intense. This phenomenon is associated with gas ionization and acceleration of ions in strong electric elds, dragging the gas particles and generating a secondary ow, known as corona wind. Corona wind may be employed as an active enhancement technique for heat transfer. Here, corona wind is used to enhance natural convection inside circular tubes and triangular ducts. The paper describes, not only the enhancement of heat transfer, but also, the shortcoming and challenges encountered in the computational modeling of corona discharge. It is shown that the solution of the electric charge density su ers from some degree of irregularity and asymmetry, while an azimuthally symmetric solution is expected. If this de ciency is not recti ed, the resulting electric body force and the predicted ow eld are not accurate. Two remedies are recommended to improve the solution, namely, arti cial viscosity and structured grids. Moreover, the present computations indicate that, for the Rayleigh number of 3737 and the applied voltage of 8.25-9.5 kV, the corona discharge enhances heat transfer by 17.9-106.9. %U https://scientiairanica.sharif.edu/article_2975_499c395288c8ffac1322f4c609e0913c.pdf