Papers by Keyword: Lattice Monte Carlo

Abstract: This work addresses the numerical analysis of anisotropic composite structures for thermal energy storage and temperature stabilization. The basic idea of heat sink composites is the combination of metallic matrices for fast energy transfer with phase change materials for thermal energy storage. Anisotropic matrices, such as lotus-type structures, allow for increased control of the thermal energy flow, without the necessity of additional thermal insulation. As an example, thermal energy can be directed towards a surface cooled by convection and excess energy is stored in the phase-change material. Computed tomography data of copper lotus-type material is used for the generation of the numerical calculation models. Due to its particular meso-structure, this material is characterised by strongly anisotropic properties. The void space of this cellular metal is filled with the phase-change material paraffin in order to enhance the energy storage capacity. A recently extended Lattice Monte Carlo method is used to evaluate the anisotropic thermal properties of these promising materials.

Abstract: Heat sinks enable the storage of energy that would otherwise be lost, thus ensuring significant energy-savings and fewer greenhouse gas emissions. Heat sinks also play the major role in the efficient temperature control of devices such as batteries. In principle, any material can act as a heat sink – traditionally, copper is used for many applications. However, copper is relatively expensive, has a high density and only a limited energy storage capacity. In contrast, a phase-change material (PCM) allows in effect an additional storage of energy through its phase change thus greatly increasing the achievable energy density. The aim of this work is the numerical analysis of the transient heat transfer in composite heat sinks containing phase-change materials. For the first time, a recently formulated Lattice Monte Carlo Method is applied to determine temperature distributions and the amount of energy transferred versus time in phase change materials.

Abstract: In this paper, we investigate oxygen in-diffusion and out-diffusion with respect to a cermet composite where oxygen segregates at the interface between the metal matrix phase and the ceramic oxide phase. This phenomenological diffusion problem is treated by overlaying it with a fine-grained lattice that was addressed using a Lattice Monte Carlo method and a little-known exact expression for the lattice-based effective diffusivity in the presence of random traps. It is shown that there is very good agreement for the oxygen concentration depth profiles between the Monte Carlo results and the exact expression.

Abstract: In this paper, the increase of the effective thermal conductivity of paraffin based heat sinks is investigated by making use of cellular metallic matrixes with open cells which are introduced in the thermal low conductive paraffin wax. Lattice Monte Carlo analyses are conducted on different model geometries of such composites composed of a cellular matrixes and paraffin wax. The dependence of the effective thermal conductivity on the cell geometry and the metal foam matrix material is analysed. Furthermore, a diamond coating is simulated in order to estimate its influence on the effective thermal conductivity.

Abstract: In this paper, a Lattice Monte Carlo method is used to determine the effective thermal conductivity in two dimensional models of adhesively bonded metallic hollow sphere structures (MHSS). In contrast to earlier approaches, more realistic distributions of spheres without the simplification of cubic symmetric arrangements are considered in this study. For the Monte Carlo analyses, two-dimensional periodic lattices representing different cutting planes through MHSS are generated. Therefore, an algorithm is used which sequentially fills the lattice by adding cut spherical shells and inclusions in the matrix. Another focus of this work is the analysis of the influence of different geometric circle distributions on the effective thermal conductivity. The findings of the random arrangements are also compared to a regular primitive cubic arrangement and with a Maxwell-type approach.