Authors: Saad Bin Mansoor; Bekir Sami Yilbas
Addresses: Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, KFUPM Box # 1913, Dhahran, 31261, Saudi Arabia ' Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, KFUPM Box # 1913, Dhahran, 31261, Saudi Arabia; King Abdullah City for Atomic and Renewable Energy (K.A.CARE), Saudi Arabia Dhahran, Saudi Arabia
Abstract: Entropy generation rate during phonon transport across consecutively placed two thin films is examined. The films are thermal disturbed via setting the temperature differential at the edges. The Boltzmann transport equation is introduced to model the micro/nano scale heat transfer across the films. Thermal resistance is incorporated at the edges and at the interface of the films to model the boundary scattering. Thermodynamic irreversibility in association with the entropy generation rate is formulated in the films while adopting the phonon intensity distribution. The thermal conductivity predictions are validated adopting the previous data. It is demonstrated that the thermal conductivity data predicted and obtained from the experiments are in good agreement. The phonon scattering at the film edges and at the interface results in temperature jump in these regions. As the film thickness reduces, the entropy generation rate becomes large, which is related to the thermodynamic irreversibility caused by temperature jump. The entropy generation rate predicted through the Fourier heating model remains significantly larger than that obtained from the phonon radiative transport model, which is more pronounced for the small film thicknesses.
Keywords: phonon transport; thin films; entropy generation; boundary scattering.
International Journal of Exergy, 2019 Vol.30 No.1, pp.86 - 101
Received: 05 Sep 2018
Accepted: 28 Feb 2019
Published online: 05 Jul 2019 *