A review on start-up characteristics of the pulsating heat pipe

Pulsating heat pipe (PHP) is a two-phase heat transfer device, and the start-up characteristics plays a crucial role in its practical application and stable operating performance. This paper introduced the start-up principle of PHP and reviewed the influences of the cross-sectional shape, the physical property parameters and the external field action (i.e., magnetic field, ultrasonic wave etc.) on the starting characteristics of PHP. Based on the results of present literature, the pressure distributions in PHP with non-circular channel section or irregular channel are uneven, which easily form an oscillation cycle motion and is beneficial to the efficient operation of PHP. Simultaneously, the fluids with high thermal conductivity, low dynamic viscosity and low surface tension (such as nano-fluid, deionised water, etc.) are more conductive to starting characteristics of PHP. In addition, reviewed studies reported that as an active heat transfer enhancement method, external field has great potential in terms of enhancing heat transfer and controlling the heat transfer process.