Experimental investigation on thermal performance of multi-layers three-dimensional oscillating heat pipes

An experimentally investigation on the effect of heating powers, layer number, operating orientations and filling ratios on three-dimensional oscillating heat pipe (3D-OHP) was studied in detail. Each layer of 3D-OHPs had the similar shape of single layer OHP with 90 mm wide, 150 mm high and 2turns. The distance between adjacent tubes and adjacent layers were both 26 mm. The thermal performance was studied by testing the start-up power, temperature and thermal resistance. Another 2D-OHP with same turns and similar geometry size as 3D-OHP was also tested to compare the difference between two OHPs. The results showed that the 4 layers 3D-OHP had the smallest start-up power and temperature among single layer to 5 layers 3D-OHPs under the similar heating powers both vertically and horizontally placed. It also had the smallest thermal resistance after start-up, which indicated that 4 layers 3D-OHP had the best thermal performance under the similar working conditions among 3D-OHPs. The 4 layers 3D-OHP with 50% filling ratio had the lowest start-up power and temperature and good heat transfer ability both vertically and horizontally placed. Compared with 2D-OHP, the thermal resistance of 3D-OHP was lower under high heating power in horizontal orientation. In general, the 3D-OHP had its unique advantages because of its multi-layer structure.