An experimental research was conducted to investigate the level of heat transfer enhancement that can be achieved by negative EHD in the developing region of a circular tube by helical electrode. The study focused on laminar to lower range of turbulent flows with Reynolds number ranging from 1500 to 10,000 and voltage from 0 to 17.1 kV. Three different constant heat fluxes were applied on the outer surface of tube. The working fluid in all experiments was air. Maximum enhancement occurred at Re=2500 and 4000, namely in the transition flow.