Water-vapor measurements of low-slope roofing materials

Burch, D. M.; Desjarlais, A.O.

doi:10.6028/nist.ir.5681

Cited by 16 publications

(18 citation statements)

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“…Essa relação é conhecida como isoterma de sorção e afeta, de forma bastante significativa, a resistência mecânica e a estabilidade dimensional de diferentes produtos. Para determinação dessa isoterma de sorção é necessária uma análise detalhada dos problemas relacionados com a umidade do material, como empenamentos na manufatura do painel e inchamento e contração na estrutura do composto (BURCH et al, 1992;WU e SUCHSLAND, 1996).…”

Section: Introductionunclassified

“…Esse fato é atribuído às altas temperaturas utilizadas, durante a prensagem, no processo de manufatura (SUCHSLAND, 1972). Alguns estudos experimentais foram conduzidos com o objetivo de determinar a isoterma de sorção de diferentes produtos compostos de madeira (HEEBINK e HASKELL, 1962;BURCH et al,1992). Nenhum desses estudos, no entanto, envolveu uma análise mais aprofundada com dados de regressão para ajuste de modelos.…”

Section: Introductionunclassified

“…A determinação desses parâmetros torna possível utilizar o Modelo Analítico de Nelson, como uma ferramenta, para prever, por exemplo, umidade que flui através das paredes de edifícios (BURCH et al, 1992) e o gradiente de umidade em painéis de revestimento de mobílias (WU e SUCHSLAND, 1996).…”

Section: Introductionunclassified

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Umidade de equilíbrio de painéis de madeira

Silva¹,

Mendes²,

Trugilho³

et al. 2005

Rev. Árvore

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Este estudo teve como objetivo a determinação da umidade de equilíbrio de painéis de madeira numa câmara de climatização e comparação dos seus valores com os obtidos através da equação de Nelson. O trabalho foi desenvolvido na Unidade Experimental de Produção de Painéis de Madeira da Universidade Federal de Lavras. Foram utilizadas amostras de aglomerado, compensado multilaminado e sarrafeado, chapa dura, OSB (Oriented Strand Board) , MDF (Medium Density Fiberboard), HDF (High Density Fiberboard), madeira-cimento e madeira-plástico, sendo esses produtos de escala industrial e experimental. As dimensões dos corpos-de-prova foram de 2,60 cm de largura por 2,60 cm de comprimento. As espessuras foram aquelas mais utilizadas comercialmente de cada produto, sendo utilizadas cinco repetições por painel. Os corpos-de-prova foram pesados e levados para uma câmara de climatização, onde foram submetidos a diferentes condições de umidade relativa (90, 80, 70, 60, 50 e 40%) e uma temperatura constante de 30 ºC. Determinaram-se a histerese e a umidade de equilíbrio, que variaram de 40 a 90%. Os resultados indicaram que a equação de Nelson se mostrou eficiente na estimativa da umidade de equilíbrio e que não existe em média diferença de histerese entre os produtos estudados, mostrando que todos apresentam a mesma estabilidade dimensional. Observou-se, também, que o revestimento dos painéis não afetou a umidade de equilíbrio.

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Section: Introductionunclassified

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Umidade de equilíbrio de painéis de madeira

Silva¹,

Mendes²,

Trugilho³

et al. 2005

Rev. Árvore

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“…If the wall is exposed to moisture variation on both sides, the effective penetration depth is Based on the permeability of the material, the material water-vapor-diffusion coefficient can be calculated [24] wheref0,fi andfz are material-specific coefficients (see Table A The multiple-node model can be formulated similarly to the Thomas and Burch model [27]. For a two-node model, the balance equations are: In order to offer an idea about the complexity of the weather-related calculations, the next section describes the algorithm used in DOE-2 for the calculation of the direct and solar radiation incident on an exterior surface.…”

Section: A74 Plenum Air Heat Balancementioning

confidence: 99%

“…Likewise, the location and orientation of the person inside the room must be known, because the mean radiant temperature often varies from point to point. The first experiments of thermal and comfort sensations to radiation experienced by seated persons were conducted by Schlegel and McNall [24], and McNall and Biddison [25].…”

Section: Thermal Comfort Considerationsmentioning

confidence: 99%

Radiant cooling in US office buildings: Towards eliminating the perception of climate-imposed barriers

Stetiu

1998

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Isotherms of water vapor sorption by light inorganic and polymer heat-insulating materials

Gnip

Veyalis

Kershulis

2006

J Eng Phys Thermophys

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This paper presents the results of an experimental study of the isotherms of water vapor sorption by glassfiber and mineral-wool products, expanded polystyrene plates, and ecowool. It has been shown that the equilibrium specific moisture content of glass-fiber and mineral wool products depends on the binder content and density and that of expanded polystyrene plates is density-dependent.As a warmth-keeping jacket of fencing constructions, glass-fiber and mineral-wool products, polystyrene foam plastic plates, and also ecowool -a loose heat-insulating material -are widely used. Rational design of fencing constructions requires knowledge of their thermophysical and mass-exchange characteristics [1][2][3]. In calculating the masstransfer coefficients, as input quantities, the equilibrium moisture-content isotherms characterizing the sorption properties of materials are used [1,2,4]. While for load-carrying and finishing coats of fences they have received a fairly exhaustive study, a large portion of information on light effective heat-insulating materials [2, 4-7] has become outdated and, moreover, was obtained for types that are no longer used [2,7], is fragmentary [5] or is devoted to narrow, exclusively practical purposes of optimization of the heat-insulating layer [6]. In [4], sparse experimental data on the equilibrium moisture content of such building materials as fiber boards (ρ = 301 kg/m 3 ), plywood (ρ = 578 kg/m 3 ), perlite boards (ρ = 173 kg/m 3 ), polyisocyanurite boards (ρ = 32.5 kg/m 3 ), and glass-fiber boards (ρ = 122 kg/m 3 ) are given.The presence of several forms of moisture-material bonding at a different air humidity, as well as the indefiniteness of the geometry of the porous structure of heat-insulating materials make it impossible to give a rigorous analytical description of the dependence of their equilibrium specific moisture content on the air humidity [1, 3, 4].In the present paper, an experimental study of the sorption isotherms has been performed and empirical dependences for light inorganic and polymeric heat-insulating materials have been obtained.The experiments were performed by the tensimetric (exciccator) method [8,9] The maximum size of specimens of any shape did not exceed 20 mm, and their mass depending on the material density was 1-4 g. The equilibrium specific moisture content at each given relative air humidity was determined by the results of testing three specimens. The preliminarily dried specimens were brought to the equilibrium state in artificially created vapor-air media having a relative air humidity of 40, 60, 80, 90, and 97% at a temperature of 20 o C. The possible error in determining the sorption moisture content by the tensimetric method, with all methodological instructions being observed, does not exceed 5% [9]. The reason for the spread of repeated determinations of W eq is mainly the non-identity (dissimilarity) of specimens. To reduce it, we used the average sampling technique [10].The experimental data on the equilibrium specific moisture content W eq (...

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Water-vapor measurements of low-slope roofing materials

Cited by 16 publications

References 4 publications

Umidade de equilíbrio de painéis de madeira

Umidade de equilíbrio de painéis de madeira

Radiant cooling in US office buildings: Towards eliminating the perception of climate-imposed barriers

Isotherms of water vapor sorption by light inorganic and polymer heat-insulating materials

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