Verification experiment of maximum hydraulic diameter in a novel three-dimensional asymmetric oscillating heat pipe

Abstract

A novel three-dimensional asymmetric oscillating heat pipe (3DAOHP) with unequal curvature radius of upper and lower bends has been designed. Setting the basic factor of diameter from 1.9 mm to 6.2 mm, a verification experiment on the criterion of conventional maximum hydraulic diameter (MHD) has been conducted. The results show that the 3DAOHP can still perform normally and transfer heat effectively, even if the diameter exceeds the MHD by 98.1 %. And the temperature profiles at each end does not show obvious abnormalities. The thermal performance also does not show any deterioration, which still follows the rule that the larger the diameter, the stronger the heat transfer capability. The thermal resistance of the 6.2 mm 3DAOHP can reach 0.07 °C/W at 1300 W without touching the dry-out limit. Moreover, the frequency and amplitude of hot end temperature fluctuation show suppression as the diameter increases. Therefore, the conventional MHD is not a diameter limitation of oscillating heat pipe (OHP) in enhancing heat transfer. Thus, the availability of OHP in high heat loads can be improved by further increasing the tube diameter. These findings are important for the OHP application in higher heat flux.