A mass-spring-damper model of a pulsating heat pipe with a non-uniform and asymmetric filling

•A non-linear mass-spring-damper model for a PHP is developed.•Good agreement with numerical and experimental results from literature.•Effective thermal resistance decreases with increasing heat input.•Four different modes of motion can be distinguished.•More translational and combined motion observed when heat input increases.

A pulsating heat pipe (PHP) is a device that transfers heat from a hot spot to a cold side by oscillating liquid slugs and vapor plugs. Its working principle is based on interplay between convective heat transfer, evaporation of the liquid at the hot side and condensation of the vapor at the cold side. Several factors play an important role including pressure differences, frictional forces, inertia forces, capillary forces and gravitational forces. The goal of this paper is to analyze the effects of non-uniform and asymmetric filling of a PHP on its thermal performance. In this paper, a 1D mass-spring-damper model is developed to predict the motion in a PHP. Also, a heat transfer model is developed. These two models are coupled to analyze the motion and performance of a PHP and can also take asymmetry into account. The model is compared with both numerical and experimental results from literature. Simulations show that including asymmetry into the system results in a good agreement with experimental results. Finally, four different modes of motion are observed: Oscillatory motion, translation, combined oscillatory-translation motion and no motion. Motion composition of a PHP as a function of heat input is studied. It is seen that translational and combined motion become dominant with increasing heat input. Also, the thermal performance of the PHP increases when the percentage of the translational and combined motion increases.

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