25 th ABCM International Congress of Mechanical Engineering October 20-25, 2019, Uberlândia, MG, Brazil COB-2019-0920 ANALYSIS OF THE FEASIBILITY OF A PARABOLIC HEAT CONDUCTION MODEL FOR SELECTIVE SURFACES THERMAL BEHAVIOR Leonardo Bitu Correia Leandro José Felix da Silva Neto Márcio Rodrigo de Araújo Souza Fabiano Cordeiro Cavalcanti Kelly Cristiane Gomes da Silva Federal University of Paraíba. Jardim Universitário, Campus I, Castelo Branco, PB, Brazil, Postal Code 58051-900 leonardo.leandro@cear.ufpb.br; josefelix@cear.ufpb.br marciosouza@cear.ufpb.br fabianofr@cear.ufpb.br gomes@cear.ufpb.br Abstract. In order to increase the efficiency of solar energy capitation in solar collectors, selective coatings formed by thin films are used. These coatings are subject to temperature variations from solar radiation which can cause changes in microfractures. The objective of this work is to evaluate if the microscale parabolic heat conduction model can be used as a tool for knowledge by thermal behavior of Selective Surfaces for thermosolar energy conversion. It evaluated the impact of the terms: coefficient related to the dimensionless power of the internal heat source (ψ 0 ), dimensionless absorption coefficient (β) and dimensionless time (τ). Therefore, it is possible use the parabolic heat conduction model in thin films as a tool for design of selective surfaces in relation to their thermal behavior. Keywords: solar collectors, selective coatings, parabolic microscale heat conduction model. 1. INTRODUCTION The simplest way to convert solar energy is thermal conversion. This type of conversion occurs in equipment called solar thermal collectors, the most common is flat plat and parabolic troughs collectors. Solar thermal conversion is commonly used for fluid heating in power cycles in the generation of electricity (Rankine Cycle) (Duffie; Beckman, 2006) . In order to increase the efficiency of solar radiation uptake, such collectors may have coatings on their absorptive surface that increase the efficiency of solar radiation absorption (Neto, 2017). These coatings are called Selective Surfaces or Selective Coatings and are subject to temperature variations from solar radiation, which can cause changes in their optical characteristics and even microfractures (Tabor, 1961). Thus, assessing the thermal stability is important to ensure optimum operation of the selective surface. The temperature of the selective coatings is directly related to its own optical and morphological characteristics (Zheng et. al., 2013). In this case, the study of the temperature gradient present in the coating due to solar heating may show evidence of how the thermal stability of a surface will behave. To estimate the temperature gradient in a coating it is important to study the heat conduction in microscale. Several mathematic models have been developed to explain the conduction of heat at the microscale for a variety of circumstances, such as Two-Equations (Yilbas, Manson and Ali, 2018), Hyperbolic (Ai, Li, 2014; Lewandowska, 2001; Torii, Yang 2005) and the Parabolic (Lewandowska, 2001; Yilbas, Mansoor, Ali, 2018). Hyperbolic and Two-Equations models were better to represent the thin film heat conduction, due they account the thermal transporters interaction (electrons and phonons) (Yilbas; Mansoor; Ali, 2018). Although the Parabolic model does not consider these interactions, this one presented close results to hyperbolic model. The mathematical effort to solve hyperbolic equations is very large. On the other hand, parabolic equations have relatively simple answers to be found. So, using the parabolic model does not generate many errors in the final answer. A good strategy to solve the Parabolic Heat Conduction Equation (PHCE) is using numeric method. Finite difference approximation can be used for this kind of application. The PHCE solution should be generalized for all kinds of thin films, so dimensionless will be used to generalize the solution.