Non-isothermal drying of fired-clay brick, an NMR study

G.H.A. Heijden, van der, H.P. Huinink, L. Pel, K. Kopinga

Research output: Contribution to journalArticleAcademicpeer-review

24 Citations (Scopus)

Abstract

Nuclear magnetic resonance (NMR) was used to measure moisture profiles during non-isothermal drying of fired-clay brick. Drying was induced by a temperature gradient resulting from one-sided heating. A saturated fired-clay brick sample which was closed and isolated on all sides except for the front surface was heated with a halogen lamp of variable intensity. By measuring the moisture profiles in time it was possible to identify two distinct drying stages. In the first drying stage homogeneous drying is observed. When the critical moisture content is reached a drying front enters the sample. The characteristic time t0 after which this drying front develops depends on the applied heat flux. The total amount of energy needed for evaporation of the moisture in the first drying stage is found to be independent of the heat flux from the lamp. As a result the total amount of moisture as a function of time can be scaled to one master curve using the time t0. The data from these measurements provided an interesting view on drying processes, not only under isothermal conditions but also under influence of a thermal gradient. By using the power input as a scaling parameter it is shown that both the total mass and the drying front positions as a function of time show the same behaviour in all experiments.
Original languageEnglish
Pages (from-to)3010-3018
JournalChemical Engineering Science
Volume64
Issue number12
DOIs
Publication statusPublished - 2009

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