Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
TRANSIENT THERMAL ANALYSIS OF A MULTILAYER INSULATED SYSTEM WITH DIFFERENT OUTGASSING RATES AND THERMAL CONDUCTIVITY.
Submission Author:
Guilherme Lacerda , RJ
Co-Authors:
Guilherme Lacerda, Marcos Curi
Presenter: Guilherme Lacerda
doi://10.26678/ABCM.COBEM2021.COB2021-1844
Abstract
An essential subject about thermal control in mechanical engineering is the variety of techniques for thermal insulation and its wide research field among the literature and actual applications. Equipment such as electronic devices depends on temperature control for applications in severe environmental conditions, for example, space-based equipment, which is the scenario under analysis. In that sense, space thermal control often uses the Multilayer Insulation (MLI) to isolate the heat flux in spacecraft to the outer environment. The MLI designing depends on specific parameters and variables that have a direct impact on its performance. Knowing how to choose an ideal combination of them is extremely important for a correct functional system, leading to an accurate prediction of the MLI performance. The parameters such as thermal conductivity, outgassing rate and spacers are on focus in this paper. The literature is predominantly based on experimental studies to calculate the performance of MLI. Due to its complexity, theoretical analysis and computational simulation of MLI performance, which provides results with high accuracy, became a research field interest to complements the analysis and reduce the costs of the experimental equipment. This paper aims to perform a numerical simulation for different outgassing rates and two different spacers, glass fiber and polymer pins, between the MLI layers and determine the temperature field and heat flux across the layers contributing to reliable theoretical data. The mathematical approach based on transient governing equations of fluid mechanics and radiation-conduction heat transfer leads to a coupled non-linear ODE system, solved by two subroutines from Python library. The temperature boundary conditions used for the numerical analysis was 4K and 300K for the outer space and the insulated surface, respectively. The results show the impact on the temperature field over the MLI layers with different parameters and better results for materials with lower outgassing rate. For glass fiber spacer, the temperature in the last layer is lower than the polymer pins. The thermal conductivity correlation of the glass fiber and the polymer pin depends on the layer temperature, and by experimental studies, it is possible to achieve an accurate expression for it. The design of the polymer pin will also impact its conductivity. Further comparisons and analysis between those different spacers and outgassing coefficients were made, predicting the behavior of the MLI system numerically with excellent results, showing the importance of each parameters accuracy.
Keywords
Aerospace engineering, numerical heat transfer, transient thermal analysis, Multilayer Insulation, Outgassing
