Link between Acoustic and Hygrothermal Behavior of Hemp Shiv and Pith Composites

Bio-based materials are an environmentally friendly alternative to classic construction materials, yet their generally low density can lead to poor acoustic properties. The acoustic performance of hemp shiv and sunflower pith composites is therefore analyzed using Kundt’s tube. Although the loose aggregates present an exceptional sound absorbing behavior, it can be notably worsened in the presence of certain binders. The Transmission Loss is nevertheless enhanced by the binders, although it does not exceed 20 dB in most cases. For both properties, the type of binder has been found to be the most influential parameter. Through the Kundt’s tube method, it is also possible to determine the geometrical parameters of the composites’ microstructure, which have been observed to be similar for materials presenting comparable hygrothermal properties and containing the same binder. In a previous work, an experimental correlation was found between the thermal conductivity and the interparticle porosity of the aforementioned composites, which is compared to theoretical thermal conductivity models from literature without finding any apparent correspondence.

Physical Properties and Hygrothermal Behavior of Mycelium-Based Composites as Foam-Like Wall Insulation Material

This research aims to study mycelium-based composites (MBC) by assessing their performance as foam-like wall insulation material. Various substrates have been selected to get optimized performance of the composite. Results showed that a prolonged growing period arose a denser mycelium outer layer in MBC, which rendered better water resistance due to the hydrophobicity of mycelium. Thermal conductivity and mechanical properties are highly dependent on substrate choices than other parameters of MBC, which coincided with the literature. Additionally, influences of accelerated aging test and moisture buffer capacity of MBC were first studied in this research. The results indicated that MBC not only maintained good functional performance after the accelerated aging test (i.e. drying and wetting cycles) but also constituted good moisture buffer capacity. This means that MBC has key material essences to apply as internal wall insulation material and become one of the layers in vapor-permeable building envelope systems to passively regulate indoor relative humidity and thermal comfort.

Experimental and Numerical Study of Hygrothermal Behaviour of a Washing Fines Hemp Test Wall

Bio-based materials are a promising tracks that offer thermal and environmental performances in order to reduce the consumption of energy and of non-renewable resources. For this purpose, in a previous study, the LGCGM worked on the development of Washing Fines Hemp composites (WFH) and characterized them on multiphysical points of view. Such materials show low thermal conductivity and high moisture buffer ability. In order to characterize their hygrothermal behavior at wall scale, a test wall is set up in an air-conditioned bi-climatic test room to simulate indoor and outdoor climates. This paper investigates the characterization of hygrothermal behavior of Washing Fines Hemp wall under typical Tunisian summer climate. It consists in an experimental study, supplemented by numerical simulation performed with WUFI Pro V6.5 software. The experimental hygrothermal response of the wall to such solicitations is analyzed from the temperature and relative humidity kinetics at several positions in the wall and from temperature and vapor pressure profiles. It shows that for daily cycles the two thirds of the thickness of the wall on the exterior side are active, as well regarding heat and moisture phenomena. More sorption-desorption phenomena are highlighted. The numerical results are consistent with experimental data for temperature and underestimate vapor pressure in the inner part of the wall.

Bioclimatic performance of wet coffee processing facilities: conditions for workers and coffee

This study aimed to evaluate the bioclimatic performance of three wet coffee processing facilities in Colombia, focused on the conditions for workers and coffee parchment, through computer simulation. In addition to temperature and relative humidity, the Wet-Bulb Globe Temperature index (WBGT) was simulated during the highest coffee production month. The proposed simulation model was able to predict hygrothermal behavior within the three coffee processing facilities. Case 3 presented the warmest environment, and case 2 the most humid environment concerning the appropriate conditions for the coffee and the worker. The WBGT index limit was exceeded in case 3. Since this type of facility emits large amounts of heat and steam, constructive modifications are suggested to improve the environmental conditions of workers and coffee. Mainly, the physical separation of the heat exchangers is recommended, which ideally should be outside the post-harvest facility. The steam produced in the drying process should be quickly evacuated with ventilation strategies. Additionally, the use of strategies that reduce the energy gain from solar radiation is suggested.

Brick of the Historical Heritage: Comparative Analysis of The Thermal Conductivity, Density and Moisture

In the renovation of historic buildings, the facades deserve special attention because, in general, it is where the property’s value and heritage lies. Additionally, they have a fundamental impact in the energetic efficiency of buildings. When you want to achieve an efficient building, the facades must comply with certain construction standards, generally difficult to achieve in renovations, especially in facades built with exposed brick, not altering their external appearance is a sine qua non condition. Against this background, in order to carry out optimal interventions in the thermal behavior of a brick wall, it is essential to have an exhaustive knowledge of the characteristics and values that influence thermal conductivity. To do so, calculations and simulations are carried out using the density and porosity parameters that are published in the different documents and regulations. However, these values are not reliable because they refer to the materials currently manufactured, and therefore, they are not valid when working with centenary materials that have been produced without quality control or precise technical specifications. On the other hand, the values provided by the regulations refer to the material in the dry state. It has not been considered that bricks, and especially those manufactured manually, due to their intrinsic conditions, are capable of absorbing large amounts of water, and therefore, of significantly varying its thermal conductivity. This feature is extrapolated to brickwork facades, where water can rise from the ground and penetrate from the rain. Thus, it is necessary that in the thermal conductivity study its hygrothermal behavior is taken into consideration. Against this background, this article presents the results of the tests carried out on specimens of various bricks from different traditional bricks factories and manufacturing processes and with an approximate age of about 100 years, to show that the old bricks have very different density, porosity and thermal conductivity values from the current ones. In addition, these values vary greatly depending on the moisture they contain, and also, the manufacturing system they had. Likewise, it is clear that the bricks of the facades of historic buildings, even if they are contemporaries, have different characteristics among them, showing different thermal behavior.

Investigation into the hygrothermal behavior of fired clay materials during the freezing of supercooled water using experiments and numerical simulations

In this study, supercooling effects on the hygrothermal behavior of fired clay materials under various experimental conditions, such as water content, cooling rates, and size of specimens were investigated using experimental methods and hygrothermal simulations. We report results of the differential scanning calorimetry (DSC) and temperature distribution changes during a freeze–thaw (FT) experiment using unsaturated specimens. Also, we developed a numerical model of the freezing and thawing processes including the supercooling processes. The DSC results show the freezing of the supercooled water in a fired clay material is considerably faster than that in cement-based materials. It was also found that the dependency of the supercooling effects on the cooling rates seemed to be small. When the water saturation of a material decreases, the rate of the ice saturation increase during the freezing of the supercooled water is decreased while the freezing points of the supercooled water was not changed considerably. The comparison of the results of the FT experiment and hygrothermal simulations show that the combination of the existed hygrothermal model and a modified kinetic equation can reproduce the rapid temperature rise during the freezing of the supercooling water in the FT experiment. Finally, the size effects of specimens on the supercooling phenomenon was discussed based on the experimental and calculation results. The freezing points got higher when a specimen was larger. Due to differences in the ratio of the surface area to the volume, hygrothermal behavior in small specimens and relatively large specimens like that of the DSC and the FT experiment, respectively were markedly different. Water in a relatively large specimen with a small ratio of surface area to volume can achieve the thermodynamic equilibrium in a short period after the freezing starts.