关键词: 脉动热管, 数值模拟, 长度比值, 启动时间, 热阻

Abstract: Pulsating heat pipe(PHP) is a high-efficiency heat transfer device with simple structure and excellent thermal performances. With phenomena such as boiling, condensation and two-phase flow, the mechanism of heat transfer and flow is quite complex and the relevant numerical investigation still needs to improve. A two-dimensional single loop closed-loop pulsating heat pipe(CLPHP) was numerically investigated by CFD software in this research. The start-up characteristics and thermal performances of CLPHP with different length ratios of the evaporation section to the condensation one were studied by volume of fluid(VOF) approach. Considering the effects of surface tension and wall contact angle, the continuum surface force model was adopted. The input power(ranged from 10 W to 40 W) and filling ratio(40%, 50%, and 60%)were applied in present numerical investigation. The motions of creation and oscillation of bubbles and vapor/liquid plugs were discussed. The numerical results were compared with experimental data of available literature. The results showed that the start-up time and the thermal resistance of CLPHP could be reduced when the input power was increased on the evaporation section. For the same filling ratio and input power, reducing the length of condensation section within a suitable range was helpful to accelerate the start-up of CLPHP and decrease the thermal resistance, while the “dry-out” occurred easily at low filling ratio. Two types of start-up, the temperature abrupt change at lower input power and the temperature gradual change at higher input power, were observed as well. The temperature oscillation feature at evaporation section can be used to determine the start-up time of CLPHP.

Key words: pulsating heat pipe, numerical simulation, length ratio, start-up time, thermal resistance