Thermal hydraulic behavior of a large dimension hybrid heat pipe/oscillating heat pipe

Abstract

Similar to the layout of an oscillating heat pipe (OHP), a quartz hybrid heat pipe (HHP) with an inner diameter of 5 mm, exceeding 59.7 % of the capillary threshold of OHP, was designed. The detailed thermal hydraulic behavior of fluid in the HHP has been revealed. It was found that the HHP undergoes a heat transfer mode transition from phase change to pulsating flow. It is also means that the liquid slugs can be dynamically and stably formed if the heat input is sufficient. The single bubble growth and the multi-bubble coalescence are two ways to form the intermittent flow. In addition, as the main flow pattern in low filling ratio (FR), the formation of annular flow is closely concerned in the behaviors of fluid. Moreover, the higher the FR is, the clearer the contour of slug flow is. At the same time, the oscillating motion can be formed easily at a high FR, resulting in a better performance of HHP in lower heat load. However, as the heat input increases, HHP with a 60 % filling ratio exhibits lower thermal resistance, achieving a minimum value of 0.08 °C/W at 100 W.

Keywords

• Heat pipe
• Capillary threshold
• Oscillating motion
• Filling ratio