Pulsating Heat Pipe: Operation in Nonlinear Regime

Abstract

The global attention toward miniaturization technologies puts compact electronic devices at the core of thermal management research. The high compact density electronic devices are very high heat-dissipating systems. The removal of this high heat flux is imperative to maintain the reliability and durability of these devices. Among many heat removal systems, Pulsating Heat Pipes (PHP) have shown both their standalone and hybrid utility. Their miniature size with wickless structure and performance in different operating conditions put them as a promising heat removing agent in small area applications, be it terrestrial or space. Despite their simple geometry, PHPs exhibit complex dynamical characteristics due to the multiphysics processes involved during the transient operation. The complex dynamics is not easy to explain while analyzing the system by the mathematical models, used to obtain operating characteristics. The interplay between the multiphysics interactions makes the system highly nonlinear, which is very sensitive to the initial conditions. Therefore, the fundamental problem lies in the understanding of the dynamics in the nonlinear regime. Nonlinear stability analysis has been carried out on a state-of-the-art model. The oscillatory behavior of the liquid slug is modeled similarly to the springmass system. The parameters related to several thermodynamic processes have been varied to capture the change in the dynamics using codimension one and two analyses. The system of non-linear differential equations, containing the conservation equations for the liquid slug and vapor plug separately, has been solved numerically using MATCONT. Bifurcation analysis shows the sudden changes in the dynamics while varying the parameters and the start-up operating conditions also match with the literature.