Influence of filling ratio on heat transfer performance of pulsating heat pipe with self-rewetting nanofluid

An experimental investigation was conducted to explore filling ratio effect on the heat transfer performance of pulsating heat pipe (PHP) charged with self-rewetting nanofluid. The filling ratio is 30%, 50%, 70%, respectively. In the experiment, the Al₂O₃/water nanofluid was mixed with n-butanol solution at a volume ratio of 2.6 to 1 to form a self-wetting nanofluid. Among them, the concentration of n-butanol solution was 0.7wt%, and the concentration of Al₂O₃/water nanofluid was 0.1wt%. Experimental results show that the self-rewetting nanofluid has an enhancement effect on the heat transfer performance of the pulsating heat pipe, but the strengthening effect is not only related to the heating load, but also is related to the filling ratio. When the filling ratio is lower, the fluidity of the working fluid becomes worse. With the increase of the heating load, some parts of PHP are easily burnt out. In addition, the high thermal conductivity of the nanofluid and the surface tension of the self-wetting fluid are not easy to play. However, when the filling ratio is too high, the average temperature difference will increase, and the average thermal resistance will increase. Therefore, in order to enhance the heat transfer performance of the pulsating heat pipe, 50% filling ratio is chosen as the optimum filling ratio in this experiment. (paper)