Eur. Phys. J. Plus (2021) 136: 333
https://doi.org/10.1140/epjp/s13360-021-01307-0

Regular Article

Entropy generation analysis in a single-turn pulsating heat pipe considering phase change modeling

¹ Department of Mechanical Engineering, Urmia University of Technology, Urmia, Iran
² Department of Mechanical Engineering, Université Laval, Québec, Canada

^a f.mobadersani@mee.uut.ac.ir, fmobadersani@gmail.com

Received: 1 January 2021
Accepted: 13 March 2021
Published online: 23 March 2021

Abstract

Pulsating heat pipes are one of the most important solutions for the daily increasing demand for high-performance cooling systems. Despite numerous studies in this field, most of the previous works, including experimental and numerical studies, take constant heat flux boundary condition into account and neglect thin-film boiling and condensation. Furthermore, an improvement in accuracy is essential for the models that consider constant temperature boundary condition. In order to satisfy the essence of accuracy improvement in modeling of constant temperature boundary condition PHPs, the present study models a single-turn pulsating heat pipe numerically, which is based on the best predictor correlations for flow boiling and condensation. Moreover, a thin liquid film is considered in the calculation of mass transfer from vapor plugs, because of annular flow assumption. All fundamental equations, except liquid-slug-energy equation, are solved explicitly. Comparison of displacement of the liquid slug, with the previous works, indicates an increase in both amplitude and frequency. In contrast to the previous mathematical models, acceptable agreement between empirical data and the present mathematical model has been demonstrated. Furthermore, entropy generation analysis has been carried out to achieve optimum operating conditions and the results have been presented for different pipe diameters. These data also depict the effect of diameter on the properties of PHP, besides entropy generation analysis. Bejan number for simulations has been derived to show heat transfer share in entropy generation. It is shown that the share of heat transfer in entropy generation also increases by the diameter.