Abstract: Using water as working fluid, the pressure drops formini-channel radiator with different height/width ratios involved withcircular disturbed flow before or behind the mini-channels wereexperimentally studied. It is found that the pressure drop increaseslinearly with the Reynolds Number. A general empirical formula was proposedto consider pressure drop as function of Reynolds Number, hydrodynamicdiameter and height/width ratio. The formula can predict flow friction ofthe similar system well. For line-wear mini-channels, the flow frictioncoefficient is inversely proportional to Reynolds number, and the value islarger than that of circle tube. The experimental results indicate that thesurface roughness is the main impact factor for pressure drop. However, thecircular cylinder disturbed flow has little influence on it. It is foundthat the circular cylinder disturbed flow which set in the front ofmini-channel can enlarge the heat dissipation.