A novel measurement theory for inventory of working fluid and vacuum pressure of heat pipe

• Published in: Journal of the Chinese Institute of Engineers 2009-09, Vol.32 (6), p.765-770
• Main Authors: Lu, Chun-Chang, Lin, Wei-Keng
• Format: Article
• Language: English
• Subjects: heat pipe; inventory; vacuum pressure
• ISSN: 0253-3839; 2158-7299
• DOI: 10.1080/02533839.2009.9671560

Heat pipes are transport mechanisms that can carry heat fluxes ranging from 10 W/cm 2 to 20 KW/cm 2 at extremely fast speeds. Therefore, heat pipes are widely used in 1U servers, notebooks, PCs, etc. A heat pipe is a heat removal device comprising a vacuum pipe that charges a certain amount of working fluid and seals the tube. Hence, the heat pipe performance depends not only on the geometric parameters such as wall thickness, tube material, and wick material but also on the thermal properties of the working fluid such as latent heat, vapor pressure, viscosity, and vacuum pressure. Traditionally, the fluid inventory of heat pipes was measured by the lost weight method, that is measuring the weight of the heat pipe first, then, breaking the heat pipe, after drying in the oven, then weighting again, and the lost weight would be the weight of the working fluid. This paper presents a new methodological concept to measure the inventory by a basic energy mass balance equation. The Measurement theory not only calculates the fluid inventory but also the vacuum pressure data. The experimental results show that when the weight percentage of working fluid was larger than 10% of total pipe weight, the relative errors were within 4% when compared with the known inventory.