Enhancement of Natural Convection in Circular and Triangular Ducts Using Corona Discharge in Air and Nitrogen

A computational effort is undertaken to investigate the effect 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 field is intense. this phenomenon is associated with gas ionization and acceleration of ions in strong electric fields, dragging the gas particles and generating a secondary flow, 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 suffers from some degree of irregularity and asymmetry, while an azimuthally symmetric solution is expected. if this deficiency is not rectified, the resulting electric body force and the predicted flow field are not accurate. two remedies are recommended to improve the solution, namely, artificial 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.