Nonlinear Analysis of Chaotic Flow in a Three-Dimensional Closed-Loop Pulsating Heat Pipe

TL;DR

This study uses numerical simulations to analyze chaotic flow in a 3D closed-loop pulsating heat pipe, revealing complex temperature oscillations and their dependence on working fluids and system structure.

Contribution

It introduces a detailed 3D numerical analysis of chaotic behavior in pulsating heat pipes, including spectral and attractor analysis, with comparisons between water and ethanol as working fluids.

Findings

Ethanol exhibits higher correlation dimension than water.

Temperature oscillations show periodic or quasi-periodic behavior.

Simulation results align well with experimental data.

Abstract

Numerical simulation has been conducted for the chaotic flow in a 3D closed-loop pulsating heat pipe (PHP). Heat flux and constant temperature boundary conditions were applied for evaporator and condenser sections, respectively. Water and ethanol were used as working fluids. Volume of Fluid (VOF) method has been employed for two-phase flow simulation. Spectral analysis of temperature time series was carried out using Power Spectrum Density (PSD) method. Existence of dominant peak in PSD diagram indicated periodic or quasi-periodic behavior in temperature oscillations at particular frequencies. Correlation dimension values for ethanol as working fluid was found to be higher than that for water under the same operating conditions. Similar range of Lyapunov exponent values for the PHP with water and ethanol as working fluids indicated strong dependency of Lyapunov exponent to the structure and dimensions of the PHP. An O-ring structure pattern was obtained for reconstructed 3D attractor at periodic or quasi-periodic behavior of temperature oscillations. Minimum thermal resistance of 0.85 degree/W and 0.88 degree/W were obtained for PHP with water and ethanol, respectively. Simulation results showed good agreement with experimental results from other work under the same operating conditions.