Dr.  Yan  Su
University of Macau,  China

Title: Phonon Energy Transfer through Thin Films Simulated by a Non-dimensional Lattice Boltzmann Method

Abstract:

In the small scale of thin films, the measured results of heat flux may have obvious deviation from the constant thermal conductivity Fourier law, in which the heat flux is linearly related to temperature gradient with continuous temperature distributions. Hence, quantitative models for phonon energy transport through thin films are important to bridge the microscopic and macroscopic heat conductions. A new phonon energy transport frequency based relaxation model based on density distribution functions is introduced to model the heat transfer in the sub- continue regime as well as the continuum regime. Both diffusive and ballistic phonon transport are modeled in a conjugate way. Two types of Knudsen numbers are defined based on the base frequency and variable frequency to represent the effects of material size and phonon transfer frequency, respectively. Dimensionless parameters are derived based on two basic coefficients, i.e., the Boltzmann constant and Planck’s constant. A Non-dimensional Lattice Boltzmann Method based on combined relaxation time model is applied to simulate the discontinuous temperature distribution fields and corresponding effective frequency based thermal conductivities. Advantages of the present method including fast speed and simple implement of the frequency effects. Discontinuous temperature distributions and energy boundary jump are quantitatively shown and validated by comparison with previous experimental results. Effects of the film thickness and phonon frequencies are illustrated.

Biography:

Dr. Su is currently an associate Professor of Electromechanical Engineering in University of Macau. She received his PhD degree from the Department of Mechanical Engineering from University of Minnesota in 2006.  In year 2000 and 2003, she obtained her Bachelor of Thermal Engineering from Tsinghua University, and Master of Mechanical Engineering from Hong Kong University of Science and Technology, respectively. Dr. Su’s research interests include Thermal Dispersion in Porous Medium, Renewable Energy Systems, Oscillating Flows, and Indoor Air Quality. She also serves as the director of the solar energy laboratory of University of Macau and associate editors of Journal of Heat Transfer (ASME) and Case Studies in Thermal Engineering (Elsevier).