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Spatiotemporal Moisture Field
(MDPI, 2024-11-02) Fuciman, Ondřej; Matějka, Libor
For monitoring capillary moisture conduction, the most important parameter is the moisture conductivity coefficient, which is a material characteristic; however, its use in practical calculations is not very common. For further development in the field of liquid moisture propagation, an automated measuring apparatus has been developed and granted a European patent. Its essence lies in detecting the liquid water content based on a well-known physical phenomenon: electromagnetic radiation in the microwave range. The determination of the spatiotemporal moisture field is the first and fundamental step for describing transportation phenomena. The moisture field thus created allows for the viewing of the moisture conductivity coefficient, which is one of the most important parameters in describing transportation phenomena as a function of moisture. The presence of water in building materials can significantly affect their physical properties, such as mechanical or thermal–technical characteristics. This may lead to unacceptable consequences, which might only manifest after a certain period of time. In the case of multi-layered structures, moisture can transfer from one material to another. Therefore, it is essential to address this process. The advantage of the software solution described by the methodology is the use of an open communication protocol in the form of a synchronized array, which is not common in typical applications of this type. The principle of separating hardware modules is also unusual for devices of this type, as it requires the independent communication of each module with the control software. Mutual communication is handled exclusively at the software level, making it possible to modify, optimize, or parameterize the procedures as needed. Upon closer examination of the wetting curves of various materials, anomalies were revealed in some of their structures. This can be advantageously utilized in the research of newly developed composite materials. The assembled system of measuring instruments, their software integration, and control provide a foundation for the practical application of the described procedures and methods for determining the moisture field of building materials. The parameterization of individual processes, as well as the open access to data, allows for the optimization of the methodology, as materials of entirely different characteristics may require an individual approach, which will certainly contribute to the advancement of science and research in this area. Currently, this work is being followed by further extensive studies, not yet published by the authors, focusing on the application of the described moisture field to evaluate the moisture conductivity coefficient as a function dependent on the material’s mass moisture content. Their application requires specific mathematical and programming approaches due to the significant volume of data involved.
Effect of Microwave Radiation on the Properties of Hydrogel, Cork, Perlite, and Ceramsite
(MDPI, 2024-08-22) Průša, David; Šťastník, Stanislav; Svobodová, Kateřina; Šuhajda, Karel; Sochorová, Zuzana
The present work analyzes the effect of releasing physically bound water from hydrogel, cork, perlite, and ceramsite on materials exposed to microwave radiation and subsequently investigates possible changes in the physical properties of these materials (water absorption and thermal conductivity coefficient). The release of physically bound water from individual materials has potential practical applications in materials engineering, for example, in the internal curing of concrete, where individual aggregates could, under the influence of microwave radiation, release water into the structure of the concrete and thus further cure it. Experimental analysis was carried out with samples of the above-mentioned materials, which were first weighed and then immersed in water for 24 h. Then, they were weighed again and exposed to microwave radiation. After exposure, the samples were weighed again, left immersed in water for 24 h, and weighed again. The focus of the study was on the ability of the aggregates to release water due to microwave radiation and on the changes in the properties (water absorption, thermal conductivity coefficient) of these materials when exposed to microwave radiation. The samples were further monitored by digital microscopy for possible changes in the surface layer of the materials. The hydrogels show the highest water absorption (1000%) and the fastest water release (45 min to complete desiccation). After the release of water due to microwave radiation, their ability to absorb water is maintained. Of interest, however, is that in the case of almost complete removal of water from the soaked hydrogel, the original powdered state of the hydrogel is not obtained, but the outcome has rather a solid structure. In the case of cork, the water absorption depends on the fraction of the material.
Increase the internal surface temperature to eliminate surface condensation on the window
(EDP Sciences, 2024-07-16) Vorlíčková, Petra; Kalousek, Miloš; Šoulová, Eva
One of the most critical places in buildings in terms of physical thermal properties are windows. This is the most frequent place where the temperature drops below the dew point and surface condensation, or mould, develops. The work deals with the study of the surface temperature courses at the critical points of window glazing and connection joints and the subsequent improvement of the initial unsatisfactory condition by using a patented technology, a conductive material without further intervention in the structure. In the case of a very unsatisfactory condition, a heating resistance wire was attached to the bar, which in combination with the bar distributes the heat to a wider area. The evaluation of the surface temperature increase was performed in a steady-state thermal analysis with fixed boundary conditions and then with the influence of the flow in a room with the heater placed under the window.
Hydrothermal performance of wooden beam on solid masonry with capillary-active internal insulation.
(EDP Sciences, 2024-07-16) Sukop, Lukáš; Ostrý, Milan
With the increasing requirements for the energy performance of buildings, there is a demand for internal insulation systems in buildings where it is not possible to apply an external insulation system for legislative reasons. Currently, there has been an upsurge in the development of diffusion-open insulation materials whose properties can compensate for the risks of damage to solid masonry walls insulated with traditional diffusion-closed internal insulation systems. The properties of diffusion-open systems are already well known. This paper focuses on the simulation of the thermal moisture behaviour of a detail of a timber beam embedment in a wall with capillary active thermal insulation in cold climatic conditions of Central Europe.
Monitoring of microclimatic conditions and the occurrenceof micromycetes in crawl space
(Faculty of Wood Science and Technology, 2024-07-03) Pobucká, Slávka; Kalhotka, Libor; Laichmanová, Monika; Šuhajda, Karel
Therisk of creating suitable microclimatic conditions for the growth and development of micromycetes in a crawl space is relativelyhigh. Spores of micromycetes can infiltrate theliving space through leaks in ceiling construction of the crawl space due topressure conditions.The study is focused on monitoring microclimatic conditions and the occurrence ofmicromycetes in the crawl space in the Czech Republic.Samples were taken from thecrawl space structures (ceiling structure and foundation walls) using sponges.Additionally, sedimentation methods were used to monitor the indoor microclimate (in the crawl space) and the outdoor microclimate.In the crawl space, spores of micromycetes ofthegeneraAlternaria, Aspergillus, Cladosporium, Didymella, Epicoccum, Sarocladium, Sordariaand Penicilliumwere detected. The relative humidity in the crawl space ranged from 50% to95% during the model year. In total, 6,659 hours were spent in the crawl space with a relative humidity of about 75%.

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