Thermal characteristics and flow patterns of oscillating heat pipe with pulse heating

In this paper, a pulsed direct current regulated power supply instead of normal continuous power supply was applied to heat the oscillating heat pipe through transparent electrical heating film which was evenly coated on the evaporation section. Simultaneous visualization and temperature measurement experiments were performed to investigate the impact of pulse heating on the temperature difference between evaporation section and condensation section, temperature fluctuation and flow behaviors of oscillating heat pipe. The experimental results indicated that the temperature difference between the evaporation section and the condensation section under pulse heating mode is highly dependent on the pulse duration and heating power. Furthermore, it was found that the pulse duration and pulse interval play an important role on the oscillating period of the temperature. Under pulse heating, instantaneous formed large amplitude oscillation is observed due to a phenomenon termed as ‘injection–contraction’ phenomenon, which simultaneously reinforces both the sensible heat transfer and latent heat transfer. When heating power equals to or is larger than 90W, pulse heating accelerates the liquid reflux to evaporation section as the heating is stopped during pulse interval. Under pulse heating mode, the regions corresponding to the safe operations of oscillation heat pipe can be also extended.