Effects of relative humidity in the convective heat transfer over flat surface using ionic wind

This study investigates the effects of relative humidity (RH) on the generation of ionic wind and the subsequent convective heat transfer enhancement over a flat surface. The overall power consumption by the positive ionic wind was found to be 2.4 times lower than that of the negative ionic wind. Despite the differences in the power consumption, both positive and negative ionic wind displayed similar average velocity at low RH levels (30-50%), while the negative ionic wind showed slightly higher average velocity compared to the positive ionic wind at higher RH levels (60-70%). Besides velocity magnitude, the velocity profile of the ionic wind along the vertical axis was also seen to change with increase in RH. On a similar note, the heat transfer coefficients of both positive and negative ionic wind was seen to decrease with increase in RH, attributed to the decrease in velocity. A comparison of the heat transfer enhancement ratio showed that the negative ionic wind produced better enhancement than the positive ionic wind, being able to enhance the heat transfer by 1.6 compared to 1.43 of the latter. (C) 2016 Elsevier Ltd. All rights reserved.