Experimental Investigation of Uneven-Turn Water and Acetone Oscillating Heat Pipes

Abstract

An experimental investigation of a new three dimensional oscillating heat pipe (OHP) with uneven turn design was conducted in order to develop a gravity-independent OHP. Different from other OHPs, the OHPs investigated herein have uneven turns. In the evaporator, the total turn number is 20 and in the condenser 14, i.e., 14 full turns and 6 half turns, which were constructed using copper tubing with an inner diameter of 1.65 mm. The water OHP was filled with water at a 62.5% filling ratio and the acetone OHP filled with acetone at a 62.7% filling ratio. Experimental results show that the uneven turn OHP developed herein can start the oscillating motion in the negative vertical position, i.e., the evaporator being above the condenser and demonstrate that the uneventurn OHPs can significantly reduce the gravity effect on the heat transport capability in an OHP. In addition, it is found that although at low power inputs the uneven turn OHP in the negative vertical position is not good as that in the positive vertical position (the evaporator being below the condenser), at high power inputs the uneven OHP in negative vertical position has similar heat transfer performance as in the positive vertical position. The uneven turn OHP achieved a thermal resistance of 0.135 °C/W with an operating temperature of 36 °C in the negative vertical position.