Assessment of suitability of some chosen functions for describing of sorption isotherms in building materialsReportar como inadecuado




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Heat and Mass Transfer

, Volume 53, Issue 5, pp 1603–1617

First Online: 12 October 2016Received: 06 April 2016Accepted: 04 October 2016DOI: 10.1007-s00231-016-1926-y

Cite this article as: Stolarska, A. & Garbalińska, H. Heat Mass Transfer 2017 53: 1603. doi:10.1007-s00231-016-1926-y

Abstract

This paper presents results of tests and studies conducted on six common building materials, used for constructing and finishing of external walls. These included: ceramic brick, silicate brick, autoclaved aerated concrete, cement mortar, cement–lime mortar and cement mortar modified with polypropylene fibers. Each of these materials is distinguished by the other structure of porousness, affecting both the course of sorption processes and the isotherms obtained. At first, measurements of moisture sorption kinetics at temperatures of 5, 20 and 35 °C were performed, each time at six levels of relative humidity. Then, when the sorption processes expired, equilibrium moisture sorption values were determined for the materials in 18 individual temperature and humidity conditions. The experimental data were used to determine the sorption isotherm courses for each material at the three temperatures. Then, theoretical analysis was performed in order to determine, which of the models available in the literature described the sorption isotherms of the concerned building materials the best. For each material and each of the three temperature values, twenty-four equations were tested. In each case, those of them were identified which ensured the best matching between the theoretical courses and the experimental data. The obtained results indicate that the Chen’s model proved to be the most versatile. It ensured a detailed description of the sorption isotherms for each material and temperature tested.

List of symbolsA, BCoefficients determined experimentally for a given system and temperature

AACAutoclaved aerated concrete

CBCeramic brick

CLMCement–lime mortar

CMCement mortar

C, DConstant

ECharacteristic energy of adsorption

K1, K2, KnConstants

KHenry’s constant

MMModified mortar

SBSilicate brick

RCorrelation coefficient

RGas constant J-mol K

TTemperature °C

W0Micropore volume

aThe amount of adsorbed substance kg-kg

am, a0Monolayer capacity kg-kg

asConstant

a″, b″Constants of Jovanovič’s function for multilayer adsorption

a, b, cExperimentally determined values

dParameter d = 1-uhigB

h = p-psRelative vapour pressure %

k, k1, k2, n, sConstant

mWater content in samples %

mdDry sample mass g

meMass in the state of moisture equilibrium g

pVapour pressure Pa

psSaturated vapour pressure Pa

tToth’s parameter

tTime h

uLWeight moisture content

uhigSaturation hygroscopic, determined experimentally

wSorption dampness %

Greek symbolsα, αmConstants

φAir relative humidity %

ρcThe density of the adsorbate g-cm

υThe volume of vapour adsorbed

ΘThe level of the mono-layer coverage of the adsorbent surface





Autor: Agata Stolarska - Halina Garbalińska

Fuente: https://link.springer.com/







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