Heat transfer and flow visualization of pulsating heat pipe with silica nanofluid: An experimental study

As heat transfer device with two-phase flow, pulsating heat pipe (PHP) has a widely application prospect in the fields of improving energy efficiency and thermal management. In order to optimize the heat transfer performance of PHP, a visualization experiment was carried out with a high-speed camera, and detailed characteristics of flow pattern variations in nanofluid PHP were obtained. The effect of SiO2-H2O nanofluid with different concentrations (0.5 wt%, 1.0 wt%, 1.5 wt% and 2.0 wt%) were experimentally investigated to analyze the thermal performance of PHP. Results demonstrate that the addition of nanoparticles on the one hand promotes the phase transition of the working fluid in the PHP, and on the other hand increases the instantaneous velocity and the driving force of working fluid. These are all benefit for the reflux of condensed liquid and effectively avoid the phenomenon of 'dry out'. Additionally, the results also indicate that there exists an optimum concentration of dispersed nanoparticles in base fluid to enhance heat transfer. The maximum heat transfer enhancement efficiency with nanofluid concentration of 1.0 wt% can reach 40.1 % at the heating power of 50 W. The present results can provide useful inspiration for the development and application of new type pulsating heat pipe. (C) 2021 Elsevier Ltd. All rights reserved.