Thermal conductivity analysis of clay pottery-gypsum composite for Moroccan construction

Thermal performances and environmental analysis of a new composite building material based on gypsum plaster and chicken feathers waste

Date palm fibre-based polymer composite panels are fabricated for thermal insulation applications using fibres extracted from locally abundant date palms in Oman. These fibres, sourced from the abundant date palms in Oman, serve as a sustainable and cost-effective alternative to conventional insulation materials. The integration of date palm fibres into polymer matrices not only enhances thermal insulation properties but also contributes to the reduction of environmental impact associated with traditional building materials. Six specimens of date palm fibre-based composites were prepared using treated and untreated fibres in a variety of matrix types with a 50:50 weight ratio, including unidirectional, cross-directional, and multidirectional orientation. The fibres from leaf sheath of date palm tree were collected and were cleaned with water and soaked for 24 hrs, later the fibres were extracted by retting method to prepare the specimens. Initially, three specimens were prepared with above mentioned orientations such as 1A, 1B and 1C and the fibres were treated with 5 % NaOH solution to improve the characteristics of fibre. The fibres were soaked in NaOH solution for the 24 hrs at a steady temperature and dried, therefore another three specimens prepared with treated fibres i.e 2A, 2B and 2C, in total six specimens were prepared by the fibres with the mentioned proportion of polymer matrix. To analyse the behaviour of the composite and determine its appropriateness for thermal insulation applications, tensile test, hardness test, impact test, water absorption test and thermal conductivity test were conducted for all the specimens. The specimens were prepared according to the ASTM standards for each test. The study found that the specimens demonstrated promising results in terms of both tensile strength and impact strength. Additionally, the panels exhibited thermal conductivity values suitable for use in thermal insulation applications.

Carbonate rocks are common formations in hydrocarbon reservoirs, and thermal recovery methods are often employed to enhance production. The success of a thermal project is highly dependent on comprehensive knowledge about the thermal behavior of any involved component. Consequently, the availability of reliable and accurate thermal property data, such as thermal conductivity, improves optimization and operation procedures in these types of operations. Measurement of thermal conductivity of carbonate rock has been a matter of extended research, yet different techniques result in different measurements and the understanding of the effect of elevated temperatures is limited. Prior researchers used transient approaches in the thermal conductivity measurements, which resulted in poor accuracy, despite having low measurement time. Moreover, the thermal conductivity of the saturated carbonate samples has not been investigated, as the existing research mainly focused on dry samples. In this study, first, thermal conductivity is measured of five different carbonate samples with a wide range of effective porosity (from 5 to more than 30 %) using a steady-state approach within a wide range of temperatures (from 40 to 150 ˚C). Then the same procedure was repeated for saturated samples to investigate the effect of saturation in different porosity and temperatures on the thermal conductivity trend and values. Results showed that in the dry samples, there is a downward trend for the thermal conductivity of all five samples as the temperature increased. For samples at similar temperatures, as the porosity of the sample increased, an increase was observed in the thermal conductivity values in dry cases, and for the porosity values above a certain value, it started to go down as we expected, and it was interpreted as the effect of mineralogy which is another crucial parameter beside the porosity in the ultimate thermal conductivity value of a porous medium. We measured effective porosity; however, the total porosity of the sample plays a much more important role in the heat transfer along the sample, and the relationship between these two porosities depends on the samples’ pore connectivity. Thermal conductivity measurement for the saturated cases carried out by a modification in the setup. Results showed a similar trend as the temperature was increased and the values were higher compared to corresponding dry sample which revealed the incapability of averaging methods as a generalized approach for saturated rock sample thermal conductivity prediction.

For laboratories within the scheme of the voluntary surveillance system for technical insulation materials in Europe (VDI/Keymark), a proficiency test is the basis for obtaining a “registered laboratory.” The VDI/Keymark is a cooperation between the VDI, The Association of German Engineers, and the Keymark Group dealing with European voluntary product certification systems, within the scope of thermal insulation materials. Registered laboratories are allowed to conduct measurements to verify the declared thermal conductivity curve of technical insulation materials under the umbrella of the quality mark “VDI/Keymark”. The initial characterization work on a round robin material for the determination of thermal conductivity at higher temperatures led to the selection of an expanded glass granulate. With all the results of the round robin tests produced by five European laboratories, the expanded glass granulate has become a very important material for establishing a reliable European level of thermal conductivity at higher temperatures with a moderate uncertainty. The German expert group “AKThermophysik” of the Association of Thermal Analysis (GEFTA, Gesellschaft fur Thermische Analyse e.V.) further initiated a round robin test for thermal conductivity in 2012. With this additional use of the expanded glass granulate, more experience with transient methods and thermal conductivity values in the extended temperature range could be obtained. A comparison with the reference curve of the VDI/Keymark indicates very good compliance for most cases. Since August 2012, comparative tests with the expanded glass granulate as a round robin material are very important. Furthermore, the European CE marking became mandatory for industrial insulation products and temperature-dependent thermal conductivity, declared by the manufacturer, was introduced as a limit value. The challenge to determine the thermal conductivity at higher temperatures for a material using different methods and apparatuses was also an important step to evaluate the level of “True Thermal Conductivity.”

The thermal conductivity (TC) of the cement is one of the important parameters used in different simulations and numerical models to find or predict the integrity of the well cement, especially if the old oil and gas wells have to be retrofitted for geothermal or Carbon Capture and Sequestration (CCS) projects. Hence, it is important to use the true value of cement thermal conductivity, which can only be achieved after long-term testing. The control samples used in this study consisted of Class G and H cement, as it is the most common cement used in the petroleum industry. The additives incorporated in the neat sample consisted of 5% Gilsonite and Bentonite. The samples were cured for 486 days and were placed in two different conditions, i.e., dry and wet. Moreover, the effect of temperature on the TC value was performed on the Class G cement, with one set of samples exposed to a 75°C (60°C for 1.5 months) water bath and the other placed in ambient conditions for almost 1 year. The testing of TC was measured throughout the curing period with the help of Thermtest Portable Measurement Platform −2. Our findings suggest that the addition of the additive to the control samples significantly influences the TC of the samples. The value of TC for dry or wet cured samples continues to evolve with the curing period and becomes consistent after certain curing periods. However, wet-cured Class G and H incorporating 5% Gilsonite kept on fluctuating till 300 days of curing and became relatively constant after that. Whereas, the TC value of neat samples became consistent after 28 days of curing. Samples that were exposed to 75°C showed lower thermal conductivity as compared to the sample exposed to the ambient condition. Moreover, an increase in the TC value was noticed when the samples were switched from 75°C to 60°C for 1.5 months and then decreased again when brought back to 75°C. This trend emphasizes the effect of temperature differential on the thermal conductivity of the cement samples. It was also noted that irrespective of the curing condition, the highest values of TC at 486 days of curing were from Class G and H. Whereas the lowest in the wet and dry cured samples were from Class H+5% GS, and Class H+5% Bentonite, respectively. This paper presents, for the first time, the long-term thermal conductivity of a sample cured under different temperatures, additives, and curing conditions for more than 450 days. Hence, the information from this study can be crucial in determining the optimal curing period for different cement types in various conditions from which the consistent value of thermal conductivity can be obtained.

Nanocomposites and nanofluids have the potential to be used widely as effective coolant materials. The motivation for this study is a belief that aggregation and percolation of nanoparticles in coolants could help explain the considerable variability in the values of thermal conductivity observed in systems containing similar components. This paper reports the results of the molecular dynamics study of the impact of aggregation and percolation of nanoparticles on the thermal conductivity in nanofluids containing aluminum oxide (α-alumina) nanospheres surrounded by polymer, polyethylene oxide (PEG400). The Reverse Non-Equilibrium Molecular Dynamics (RNEMD) [1] approach implemented in the open source code Molecular Dynamics Simulator LAMMPS [2] was utilized for the simulations. The values of the effective thermal conductivities obtained from the RNEMD simulations increased with growing aggregation from 0.4 W/m•K to 0.8 W/m•K for the structures with no aggregation and with a percolation channel, respectively. Equilibrium Molecular Dynamics (EMD) simulations of these system were also performed as an alternative method to study the thermal conductivity. The existence of the elastic modes in the nanoparticles/matrix superstructure was confirmed. These non-propagating elastic modes do not influence directly the heat flow but their presence in nanocomposites and nanofluids affects the applicability of EMD as an adequate tool for determining the value of thermal conductivity in such systems.

To find out the best thermal conductivity value on the volume fraction of ironwood polyester filler composite (Eusideroxylon Zwageri) and to determine the effect of the number of voids on the value of the thermal conductivity of the ironwood polyester composite composite (Eusideroxylon Zwageri). This study uses an experimental method by conducting thermal and microstructure conductivity tests to see the many voids that have formed. The object in this study uses ironwood powder. Data analysis techniques in this study used descriptive data analysis which is describing research results graphically in a table. Input parameters in analyzing data include variations in the mixture of ironwood powder and resin (20% -80%, 25%: 75% and 30%: 70%), and 100% resin. The results of the study of the effect of the volume fraction of ironwood polyester composite composites on the value of thermal conductivity decreased with increasing volume of ironwood powder with the smallest thermal conductivity value at 30% volume fraction of ironwood powder : 70% polyester resin matrix that is 0.041 W/moC. The influence of the amount of voids on the thermal conductivity value of ironwood polyester composite composites can be seen that the more voids the smaller the thermal conductivity values. The number of voids along with the increasing volume of ironwood powder.

Gypsum-based mortars were widely used during the Mudejar artistic period in Spain from the 12th to 16th century. During restoration works, compatibility between the new repair mortars and the original components is essential for an adequate intervention on the monument. The increasing interest of knowing the properties of the gypsum-lime-based mortars for restoration purposes justifies the research carried out. Different mortars compatible with traditional building materials were elaborated by varying the binder proportions, the type of aggregates, the binder/aggregate ratios and the curing time. The main goal of this paper is to characterize the mechanical behaviour and the pore structure of the mortars as a function of curing time. The influence between the different variables used to prepare the mortars and the development of the carbonation process over time is also considered. Mechanical strength and porosity measurements as well as X-ray diffraction and thermal analysis were performed after curing times of 1, 28 and 90 days. The results obtained confirmed a progressive increase in mechanical strength linked to the carbonation of the mortars prepared. Less lime binder and also aggregate contents showed the highest rise in strength over time, related to the highest initial porosity which favoured the carbon dioxide flow. The use of siliceous aggregates (GL-QS mortars) obtained the best results in the development of physico-mechanical properties over curing time. The knowledge obtained from the studied mortars provides practical information to establish a suitable mortar mixture for restoration works on historic buildings and modern architecture where gypsum-lime-based mortars are used.

Effective thermal conductivity of a gypsum mortar using harbor sediments

Thermophysical characterization of oil palm shell (OPS) and OPS char synthesized by the microwave pyrolysis of OPS

This research aims at comparing the thermal performance of walls made from traditional and alternative building materials. The experimental study involves five types of walls were studied based on perforated ceramic bricks and a mixture of clay, sand with various straw proportions. Specialized software and the finite element method (FEA) were employed for modelling of the thermal processes and their visualization for the different types of walls. A simulation modelling algorithm was developed. The models developed show very good convergence of the results and provide for subsequent design and thermal calculation of constructions made by environmentally friendly materials.

Superconducting digital microelectronics require multi-gigahertz bandwidth performance of the signal I/O system, including multi-channel flat flexible I/O cables. The limited information on the thermal conductivity of modern engineering materials available to the designer of low temperature, high performance systems and devices, makes it difficult to optimize a design or even to know if it will perform as specified. This is particularly true of the newer dielectrics for which bulk thermal conductivity data do not exist. This paper presents the thermal conductivity measurements we have made of various metals and dielectrics commonly used for high performance, low loss flexible I/O cables and presents the design tradeoffs that these materials offer the designer. We also describe the relatively low cost procedure we are using to make thermal conductivity measurements of metals and dielectrics between 8 K and 100 K that satisfy design engineering requirements. A discussion of the value of thermal conductance vs. bulk thermal conductivity is also presented.KeywordsGround PlaneCryogenic TemperatureCopper FoilSignal LineContact ImpedanceThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Pentaerythritol with alumina nano additives for thermal energy storage applications

Introduction. The susceptibility of traditional building materials to corrosion has a negative impact on the durability of bridge structures. The solution to the problem of bridge durability is the use of corrosion-resistant fiber-reinforced polymer composites as the main load-bearing elements of superstructures. The joint performance of composites and traditional building materials ensures the most efficient use of the strength potential. The purpose of the study is to unify the design of superstructures, having load-bearing elements made of fiber-reinforced polymer composites by applying a well-known design solution to typical lengths of superstructures to increase the competitiveness of hybrid structures.
 Materials and methods. Unified parameters of hybrid superstructures are determined. Unification is carried out through the calculation and design of each individual span size. Since the calculation pattern is identical for each structure, the same algorithm, developed by the authors, is employed to make calculations for each span length. The calculation of the roadway slab is performed using the engineering method of “the imprint”. Calculations of fiberglass elements of the main trusses are made using finite element models of hybrid superstructures with account taken of the characteristics of the materials used.
 Results. Calculations were made and four hybrid superstructures, having main load-bearing elements made of fiberglass, were designed; a well-known unified design pattern was implemented in the designed elements. The main performance indicators of unified superstructures are determined and compared with those of similar structures made of traditional building materials.
 Conclusions. A unified line of hybrid superstructures, having standard lengths, has been designed. Each has a set of structural drawings, which can be used both at the stage of the trial design of structures and at the stage of the project documentation development. Advantages of composite polymer materials, namely, their applicability in hard-to-reach areas of the country, are demonstrated.

A disordered Nd:SrLaGa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> (Nd:SLGM) laser crystal was grown by the Czochralski method. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were measured. Thermal conductivity values along the - and -axes were found to be 1.95 and 1.70 W m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively, near 30°C, neither of which are as high as the previously reported value of 11 W m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . It was found that the thermal conductivity increases with increasing temperature, which is similar to the behavior of glass. The polarized absorption and emission spectra were measured at room temperature, and Judd-Ofelt analysis was carried out to calculate the fluorescence branching ratios and the fluorescence lifetime. The stimulated emission cross-section for the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2</sub> → <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11/2</sub> transition was calculated to be 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-19</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Finally, a diode-pumped laser experiment at 1.06 μm was performed. The highest peak power achieved was 1.16 W with an optical slope efficiency of 11%. The results indicate that Nd:SLGM is a promising material for use as disordered laser medium.