Thermal performance enhancement of an oscillating heat pipe with external expansion structure for thermal energy recovery and storage

In this paper, an oscillating heat pipe (OHP) with external expansion structure and compact layout for thermal energy recovery and storage was designed and fabricated. The thermal performance of the OHP with different filling ratios (FRs) of self-rewetting fluid under continuous heating mode was tested at first. Then pulsing heating mode and alternate heating mode were explored to enhance the heat transport performance. The temperature fluctuation characteristic and the thermal resistance under different heating modes and heating periods were compared and analyzed. The result showed that the OHP can function well and sustain large heating power under appropriate range of FR. The pulsing mode and alternate mode are both helpful to increase the fluctuation frequency and amplitude of evaporator temperature. For the condition of relative low heating power and short heating period, the enhancement effect is more obvious. The thermal resistance at 100 W can be reduced by more than 10% when the heating period varies from 2 s to 10 s. Under short heating period of 0.4 s, the thermal resistance of the OHP under pulsing heating mode at 200 W can be even reduced by over 30%.