Vibration-enhanced performance of asymmetric channel flat-plate pulsating heat pipes: Reducing thermal resistance and start-up time under dynamic loads

Abstract

As a highly efficient heat transfer device, the pulsating heat pipe (PHP) has seen widespread application in recent years. However, the mechanisms by which its performance is affected by environmental factors such as vibration have not yet been fully clarified. To address this gap, the present study experimentally investigates the start-up and heat transfer performance of an asymmetric-channel flat-plate PHP under varying heating powers, vibration frequencies (0 Hz, 25 Hz, 50 Hz, 75 Hz), and vibration amplitudes (0 mm, 0.4 mm, 0.8 mm, 1.2 mm). The results show that the asymmetric microchannel structure leads to local liquid slug retention under non-vibrational conditions. Vibration enhances fluid circulation, reduces slug stagnation, and improves thermal transfer efficiency. This results in shorter start-up time and lower start-up temperature. With increasing vibration frequency, the start-up time of PHP is gradually reduced. At a heating power of 60 W, vibration frequency exhibits a positive effect on start-up performance, achieving optimal results at 75 Hz. Vibration amplitude exerts a stronger influence on the heat transfer performance of the PHP. An amplitude of 0.8 mm was found to be the most effective, as it facilitated gas–liquid two-phase flow and improved heat transfer efficiency. When the heating power was between 10 W and 30 W, the influence of vibration on thermal resistance was minimal. However, at 40 W to 60 W, vibration significantly reduced thermal resistance. At 60 W, the thermal resistance reached 0.53 K/W under vibration, a reduction of 30.26 % compared to the non-vibrational condition.