Experimental Investigation on Operating Limitation of an Oscillating Heat Pipe

This research represents an experimental investigation on the operating limitation of an oscillating heat pipe (OHP). The OHP has six turns and three sections: evaporator, condenser and adiabatic sections with lengths of 40 mm, 64 mm and 51 mm, respectively. Water or a mixture of water and alumina (Al₂O₃) making up a nanofluid served as the working fluid. Filling ratios ranging from 30% to 70%, and tilt angles (orientation) ranging from 0° to 90° were studied. The experimental results showed (1) the water/Al₂O₃ nanofluid can enhance the OHP heat transfer performance, i.e., the highest input power (operating limitation) increased when the OHP was charged with water/Al₂O₃ nanofluid; (2) the operating limitation increased as the filling ratio increased from 30% to 70%, but the optimum filling ratio of the OHP is 30% or 50% when the working power is lower or higher; and (3) the thermal resistance of the OHP decreased as the tilt angle increased, and the operating limitation increased as the tilt angle increased.