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

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