  Numerical study has been conducted for the chaotic flow in a multi-turn
closed-loop pulsating heat pipe (PHP). Heat flux and constant temperature
boundary conditions have been applied for heating and cooling sections
respectively. Water was used as working fluid. Volume of Fluid (VOF) method has
been employed for two-phase flow simulation. Volume fraction results showed
formation of perfect vapor and liquid plugs in the fluid flow of PHP.
Non-linear time series analysis, power spectrum density, correlation dimension
and autocorrelation function were used to investigate the chaos. Absence of
dominating peaks in the power spectrum density was a signature of chaos in the
pulsating heat pipe. It was found that by increasing the filling ratio and
evaporator heating power the correlation dimension increases. Decreasing of the
autocorrelation function with respect to time showed the prediction ability is
finite as a result of chaotic state. An optimal filling ratio of 60% and
minimum thermal resistance of 1.62 K/W were found for better thermal
performance of the pulsating heat pipe.
