Thermal effusivity estimation of polymers in time domain

• Autor(a) principal: Lima,Gustavo Meirelles
• Data de Publicação: 2011
• Outros Autores: Lima e Silva,Sandro M. M. de
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Society of Mechanical Sciences and Engineering (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1678-58782011000400002
• topic: heat conduction; experimental methods; optimization; thermal effusivity

An accurate knowledge of thermophysical properties is very important, for example, to optimize the engineering design and the development of new materials for many applications. Thermal effusivity is a thermal property which presents an increasing importance in heat conduction problems. This property indicates the amount of thermal energy that a material is able to absorb. The estimation can be done by simulating a transient heat transfer model. In this case a one-dimensional semi-infinite thermal model is used. A resistance heater in contact with the sample generates a heat pulse. Variations of temperature and heat flux are measured simultaneously on the top surface of the sample. In this work, thermal effusivity is estimated in time domain through the minimization of the objective function, defined as the square difference between experimental and theoretical temperatures. The golden section technique is used for minimizing this objective function. A sensitivity analysis and a comparison between the semi-infinite and the finite models were also done to define the number of points to be used in the estimation. Measurements were carried out with three different polymers: polymethyl methacrylate, polyvinyl chloride and polyethylene. In all cases studied the results are in good agreement with literature. In addition, an uncertainty analysis is also presented.