Métricas de preservação e simulações computacionais como ferramentas diagnósticas para a conservação preventiva de coleções: estudo de caso no Sítio Patrimônio Mundial de Congonhas - MG

Abstract

This thesis investigates application of thermal and fluid dynamic computational simulations of indoor climate variables, as diagnostic tools aiming at preventive conservation of collections, including aspects of constituent materials, deterioration agents and mechanisms and their interaction with microclimate. It debates how simulation results can be used for obtaining measurable and comparable parameters - preservation metrics - and the practical use of such metrics in preventive conservation, with focus on their relationship with natural ventilation. The case study presented is the Chapel of Last Supper located at the Sanctuary of Bom Jesus de Matosinhos in Congonhas, Minas Gerais, Brazil, a UNESCO World Heritage Site. The building houses wooden polychrome sculptures by the main Brazilian baroque sculptor, Aleijadinho. The text contextualizes the studied problem in the fields of Conservation Science and related areas, with emphasis on Sustainability Science. They address the use of natural or forced ventilation as a sustainable strategy for environmental management and the potential of the fluid dynamic simulations in the conservation of Cultural Heritage. The methods and main results include: Preparation and conformity checking of RH and T sensors; Continuous in situ environmental monitoring (T and RH) during 15 months; Processing of field acquired and meteorological data; External and internal climographs obtained from field data monitoring; Determination of safe limits of environmental fluctuations for the case study by Bratasz-Koslowski and Camuffo-Pagan methods; Determination of potential use of natural ventilation for the case study; Simulations of internal climate conditions using the Energy Plus software and a predictive model by multiple linear regression; Fluid dynamic simulations using Ansys CFX ©; Validation through wind tunnel measurements; Derivation and analysis of several preservation metrics, from field acquired and simulated data. The results show that among investigated deterioration mechanisms, physical-mechanical deterioration offers the lowest potential risks, related to microclimatic fluctuations inside the Chapel. Chemical deterioration risks were considered of low relevance. On the other hand, risks of biological contamination by micro-organisms are significant, particularly in the summer, due to high temperature and relative humidity. Despite they demand a fair amount of knowledge and good sense as well as significant hardware and software resources, use of preservation metrics allow a quantitative, measurable, standardized, reproducible, easily understandable and communicable assessment of collections conservation conditions, as well as of the risks to their preservation, due to environmental deterioration agents.