Thermal Proprieties Research Articles

Thermal Parameter Estimation of Sandwich Panel using Numerical Solution of Inverse Heat Conduction Problem

In this work, a numerical formulation to solution of the inverse heat transfer problem, based in the implicit finite difference method and Monte Carlo method, is developed to estimate the thermal properties of the sandwich panel. It is realized the sensitivity analysis of the parameters and the thermal contact resistance along the layers interface is used. Experimental results of temperature are used in the numerical formulation to determine the thermal properties (conductivity and the specific heat) of the layers materials and to predict the thermal behavior of the panel. The results obtained show that the formulation estimates with adequate accuracy the material thermal proprieties.

Transient Heat Transfer Analysis in Metal Plates with Variable Thickness

Nonlinear transient heat transfer via conduction–radiation is a dynamic topic of long-standing interest with applications ranging from aeronautical and mechanical engineering to industrial and civil security. To gain a better understanding of the performances of materials having thermal proprieties that change during nonlinear heat transfer, several studies using the finite element method (FEM) have been conducted. Such studies apply nonlinear thermal material characteristics to describe the complete system under different loading conditions in each region by adjusting the temperature values for the other three edges and the thickness parameter with Dirichlet boundary conditions. As a result, while modeling and simulating temperature distributions for such situations, nonlinearities generated by temperature-dependent thermal conductivity must be considered. In this work, we focus on the analysis of coupled transient heat transfer through two metal plates with temperature-dependent thermal characteristics in which the temperature is fixed along the bottom edge and heat is transferred from both the top and bottom faces of the two plates. FEM is employed to solve the nonlinear heat equation and compute the temperature as a function of time for variable thickness. The study examines the effect of modifying the thickness parameter values on the temperature distribution over time for various edge values over 5,000 s.

Optimizing the Building Refurbishment Process Using Improved Evolutionary Algorithms

An optimization model that may be applied to analyze building retrofit strategies is presented in this research. The aim of this research paper is to identify the optimal thermal envelope configuration that will assure the minimum energy requirement for heating in the case of a residential building, while also considering price restrictions obtained through a specific market survey. To achieve this, several values for the following parameters are considered: thermal insulation materials’ conductivities and thicknesses, windows’ overall heat transfer coefficients and total solar energy transmittance and doors’ thermal proprieties. Additionally, this paper presents a method used to find the best option from among the available heat pumps that could cover most of the energy requirements for heating and domestic hot water systems, also considering the products’ prices. The proposed method is based on a Non-dominated Sorting Genetic Algorithm II (NSGA-II) model developed in the Pymoo (Multi-Objective Optimization in Python) library. The result shows that the energy requirement for heating can be reduced by up to approximately 75% compared to that obtained in the case of a non-insulated building by using suitable insulation materials and doors and windows with superior thermal proprieties chosen by the NSGA-II.

Iron(III) Sulfate-Mediated Synthesis of 2,5-Furandicarboxylic Acid Dimethyl Ester from Galactaric Acid

2,5-furandicarboxylic acid (FDCA) is one of the most studied bio-based monomers, being considered the best substitute for fossil-derived terephthalic acid in plastic production. FDCA is employed in the preparation of polyethylene furanoate (PEF), demonstrating superior mechanical and thermal proprieties compared to the widely used polyethylene terephthalate (PET). Nevertheless, FDCA synthesis mostly relies on the oxidation of the bio-based platform chemical hydroxymethyl furfural (HMF), whose notoriously instable nature renders FDCA yield and industrial scale-up production complicated. On the contrary, FDCA esters are less studied, even though they have greater solubility in organic media, which would favor their isolation and potential application as monomers for PEF. On these premises, we report herein an alternative green synthetic approach to FDCA methyl ester (FDME) using galactaric acid as the substrate, dimethyl carbonate (DMC) as the green media, and Fe2(SO4)3 as the heterogeneous Lewis acid. Optimization of the reaction conditions allowed the selective production of FDME in a 70% isolated yield; product purification was achieved via flash column chromatography over silica. Furthermore, it was possible to employ up to 5.0 g of galactaric acid in a single reaction, leading to a good isolated yield of FDME.

CFD Modeling of the Microclimate in a Greenhouse Using a Rock Bed Thermal Storage Heating System

The rock bed heating system is a more cost-effective concept for storing thermal energy use in greenhouses at night during the cold winter season. This system is considered an environmentally friendly solution compared to conventional heating systems that rely on fossil fuels. Despite the abundance of research on thermal energy-based heating systems, only limited work on climate modeling in greenhouses using rock bed heat storage systems has been reported. To fill this research gap, this study aims to simulate the microclimate in a greenhouse equipped with a rock bed heating system using computational fluid dynamics (CFD) models. User-defined functions have been implemented to account for the interactions between the plants and the air within the greenhouse. Crop rows and rock bed blocks have been considered as porous media with their dynamic and thermal proprieties. The model’s accuracy was approved by comparing simulated and experimental climate parameter data from the greenhouse. The model’s ability to predict temperature, humidity, and air velocity fields in the greenhouse as well as in the rock bed system during both phases of energy storage and restitution was demonstrated. The thermal, dynamic, and hygric fields were accurately replicated with this numerical model. The growing zone had a vertical temperature gradient between the ground and the greenhouse roof, as well as high humidity. The distribution of temperature fields along the rock bed blocks showed a significant temperature gradient between the air inlet and outlet in the blocks during the two phases of heat storage and restitution. As a result, the model could be useful for sensitivity studies to improve the performance of this thermal storage heating system.

Numerical Investigation on Auxiliary Heat Sources for Horizontal Ground Heat Exchangers

Human interference with the Earth’s climate cannot be ignored any longer. Renewable energy sources need utmost attention in all energy sectors. For buildings, geothermal energy for heating, cooling, and domestic hot water is a sustainable solution. Horizontal ground heat exchangers (HGHE) demonstrate promising results with low installation costs. Research is focused on increasing their thermal performances by structural improvements and ground thermal proprieties improvements, with little research on using auxiliary heat to increase their performances. A numerical model for an HGHE was established to investigate the effects of auxiliary heat sources on the performances of the HGHE. The results demonstrate that heat transfer into the HGHE increases the overall ground temperature at the end of the heating season by 138.50% compared with no heat transfer from auxiliary heat sources. The ground freezing period decreased by approximately 24.74% by having a heated basement, approximately 40.20% by transferring heat with solar thermal panels, and approximately 62.88% by using both auxiliary heat sources. The difference between the undisturbed ground temperature and the ground temperature with no auxiliary heat sources at the end of the season was 3.45 °C. The difference between the undisturbed ground temperature and the ground temperature with all auxiliary heat sources resulted in 0.92 °C.

Thermal proprieties and decomposition kinetics of asphalt binder modified by thermoplastic polymer and nanoclay Dellite 43B

Thermal proprieties and decomposition kinetics of asphalt binder modified by thermoplastic polymer and nanoclay Dellite 43B

Modulation of electronic and thermal proprieties of TaMoS[formula omitted] by controlling the repulsive interaction between Ta dopant atoms

We theoretically study the electronic and the thermal characteristics of Tantalum, Ta, doped Molybdenum disulfide, MoS2, using density functional theory. It has been shown that the MoS2 monolayer is not a good material for thermoelectric devices due to its relatively large band gap. We find that a Ta doped MoS2 forming a TaMoS2 monolayer can be useful for thermoelectric devices. The particular attention of this work is paid to the interaction effect between the Ta atoms in the MoS2 structure. We find that the interaction type is repulsive. It introduces an asymmetry in the density of states, DOS, reducing the band gap. In the presence of a strong repulsive interaction of Ta–Ta atoms, new states in the DOS around the Fermi energy are found leading to a reduction of the band gap. Consequently, a high Seebeck coefficient and figure of merit are seen over a wide range of energy around the Fermi energy. In contrast, a small reduction of the band gap and a vanishing degeneracy of the valence and the conduction bands are observed for the case of a weak Ta–Ta repulsive interaction leading to less promising thermoelectric properties.

Design and analysis of compound structures integrated with bio-based phase change materials and lattices obtained through additive manufacturing

Phase change materials (PCMs) are an interesting category of materials employed in latent heat thermal energy storage, such as ad hoc designed heat exchangers. Nowadays, there are several typologies of PCMs, which derive from the wastes of the agricultural industry, which could be used for this kind of design. Each material made of biological waste has a different melting/solidification point and latent heat of fusion/solidification, which means flexibility of design on the heat exchangers by considering the different thermal proprieties of the chosen material. Also, using recycled material from wastes can lead to an overall improvement of the resources and goes hand in hand with the need of today’s society to aim more and more at a Circular Economy. The industrial development of this kind of material is limited by its thermal properties, such as poor thermal conductivity both in liquid and solid phases, leading to low heat transfer effectiveness. To overcome these limitations, in this paper, the bio-based PCMs were integrated into a metallic reticular structure made of copper and aluminium and realised through Indirect-Additive Manufacturing, to improve the overall thermal conductivity of the system and increase the efficiency of the heat transfer. Four compound structures filled each time with four different PCMs were realised and tested, in order to thermally characterise each combination of materials used and choose which one has an overall better thermal behaviour. The results showed how the thermal storage/release was improved by 10% for the copper reticular structure, even if must be considered the tradeoff between better thermal management and the increase of the costs and the weight of the designed heat exchanger.

Crustal architecture, heat transfer modes and geothermal energy potentials of the Algerian Triassic provinces

The Triassic province is located within the Eastern Algerian Sahara, towards the Eastern edge of the M'zab Dorsal. Several hydrothermal reservoirs have been identified within this area along the Oued Righ valley and Rehabi-Berriane structural axis, forming an area of high temperature geothermal activity. The genetic mechanism of this geothermal system is currently unclear and needs urgent scientific reaction. In this work, we present a new conceptual model of the geothermal system in the Triassic provinces, using the structural model obtained through integrated study of recent edge detection techniques and the calculation of thermal proprieties of the middle and the lower crust. This multidisciplinary approach proposes a novel heat transfer mechanism and reservoir architecture within the province. We used spectral analysis on aeromagnetic data to determine the Curie point depth, geothermal gradient, heat flow, and radiogenic heat production. The results outlined the major structural trends within the Eastern Algerian Sahara. Deep heat flow sources were observed between 12.5 to 23 km depths and the geothermal gradient within the lower crust reaches 35 °C/km. The measurement of the thermal properties in petroleum wells indicates different thermal distributions. The delineated geothermal pattern is linked to the deformation of the Moho and the presence of deep-seated faults along the middle and lower crustal boundary. The shallow Curie point depth can be interpreted to be a result of the crustal thinning giving the high heat flow values. These results provide a physical representation of the heat transfer modes in the Oued Righ and constitute a unique continuous geothermal system within the eastern Algerian Sahara.

Spectroscopic and structural studies, thermal characterization, optical proprieties and theoretical investigation of 2-aminobenzimidazolium tetrachlorocobaltate(II).

In this study we present the crystal structure, spectroscopic and thermal behavior, Hirshfeld surface analysis, and DFT calculations of a new organic-inorganic hybrid compound (C7H8N3)2[CoCl4]. This compound crystallizes in the centrosymmetric space group P1¯. Single-crystal X-ray diffraction analysis indicates that structure consists of a succession of mixed layers formed by organic cations and inorganic anions parallel to the (001) plane and propagate according to the c-axis. Layers further are assembled into a 3D supramolecular architecture through N-H…Cl hydrogen bonds and π…π interactions. The peak positions of the experimental PXRD pattern are in agreement with the simulated ones from the crystal structure, indicating phase purity of the title compound. The presence of the different functional groups and the nature of their vibrations were identified by ATR-FTIR and FT-Raman spectroscopies. The tetrahedral environment of Co2+ was confirmed by UV-visible spectroscopy, where the spectrum shows three weak absorption bands in the visible range due to d-d electronic transitions 4A2(F) → 4T2(F), 4A2(F) → 4T1(F) and 4A2(F) → 4T1(P) typical of Co(II) coordination compounds. The direct and indirect optical band gap values were determined by Tauc method. The optimized structure and calculated vibrational frequencies were obtained by density functional theory (DFT) using B3LYP functional. TGA and DSC coupled to mass spectrometry (MS) experiments under argon atmosphere in the temperature range (25-950 °C) were carried out in order to determine the thermal stability of the title compound.

Do energy performance certificates allow reliable predictions of actual energy consumption and savings? Learning from the Swiss national database

The thermal performance gap in buildings is defined as the difference between the theoretical and the actual energy consumption for heating, and is known to undermine energy retrofit strategies and policies. This study examines the performance gap in retrofitted buildings using the Swiss Cantonal Energy Certificate for Buildings (CECB) database, using a sample of 1172 buildings for which both theoretical and actual metered consumption were known. We found an average negative performance gap of –23% for pre-retrofit buildings (actual consumption smaller than calculated) and instead a good approximation of actual consumption with theoretical consumption after retrofitting (a positive gap of 2%). A regression analysis on the energy performance certificate input parameters characterizing the building led to the conclusion that these are poor predictors of actual consumption compared to the theoretical calculation: parameters such as the energy label and the thermal proprieties of the envelope (U-values) have minor explanatory power for the actual consumption despite explaining a high degree of change in the theoretical consumption. Analysis of the indicator Energy Savings Deficit (ESD) shows an overestimation (of 37%) of the achievable savings on the basis of the theoretical consumption, whereas the prediction of savings using measured consumption before retrofit resulted in a good agreement with the actual savings (3.6% overestimation). This implies that energy savings can be estimated rather accurately by comparing the actual current consumption with the expected theoretical consumption defined by the certificate after retrofit.

Theoretical Characterization of Thermodynamic, Magnetic and Electronic Proprieties of Full-Heusler Co2YGa (Y = V, Cr and Mn) Alloys

The electronic structure, magnetism and thermal proprieties of the full-Heusler alloys Co2YGa (Y [Formula: see text] V, Cr and Mn) have been investigated by first-principles calculations based on density functional theory with the generalized gradient approximation (GGA). Our obtained results of lattice parameters show reasonable agreement to the previously reported experimental and other theoretical studies. The calculations show that all Co2YGa (Y [Formula: see text] V, Cr and Mn) alloys belong to half-metallic compound with a magnetic moment of 2.00, 3.00 and 4.00 [Formula: see text] at their respective equilibrium lattice constants which is in good agreement with the Slater–Pauling rule and perfect 100% spin polarization at the Fermi level. The thermal effect on the macroscopic properties of these alloys is presented such as the thermal expansion coefficient, heat capacity and Debye temperature, based on the quasi-harmonic Debye model.

Thermal characterization of a new bio-composite building material based on plaster and waste chicken feathers

The building materials used in Morocco characterized by a low thermal resistance which generates a huge expense in terms of energy consumption. Promoting new sustainable construction and insulation materials become a necessity. This research study aimed to develop the thermal proprieties of plaster building material by mixing it with waste chicken feathers (WCF) in order to be used as wall exterior rendering. For the purpose of determining the thermal properties of the biocomposite material Plaster-WCF, several experimental measurements of thermophysical proprieties had been performed in order to determine apparent density, thermal conductivity, and thermal diffusivity using the hot plate method in steady-state regime and the Flash method, respectively. The results showed that the addition of waste chicken feathers leads to a remarkable reduction in apparent density of about 12.3%, the thermal conductivity and diffusivity have been reduced by about 30.2% and 18%, respectively, which shows the interest of using this biocomposite material in the construction buildings in order to ensure thermal comfort and reduce greenhouse gas emissions (CO2).

Energy performance and thermal proprieties of three types of unfired clay bricks

The demand of air conditioning and heating for thermal comfort represents about 50 % of the energy consumption in the building, the energy is mainly supplied by conventional fossil fuels. Solutions must be found to reduce greenhouse gases. The building materials used in Morocco have a low thermal resistance which generates a huge expense in terms of energy consumption. Thus, a promising alternative for exploitation of insulating and ecological materials such as the unfired clay that can provide thermal comfort without using the heating or other air conditioning systems. In order to study the thermal performance of this environmental material, three types of unfired clay were taken from three different regions (Tamansort, Essaouira, Marrakech) and were characterized using the flash method and hot plate method in order to measure the thermal effusively and the thermal conductivity respectively. Then three types of envelopes built by these bricks were simulated to determine their thermal behaviors according to the meteorological data of Marrakech which is characterized by a dehydrated climate.

A comparative study of different winemaking by-products derived additives on oxidation stability, mechanical and thermal proprieties of polypropylene

Three different solid wine wastes (peels, seeds and stalks) have been mixed with polypropylene (PP) and tested as stabilizers. Their stabilizing activity has been compared with that of a commercial tannin extract powder, rich in polyphenol. Thermogravimetric analysis, Oxidation Induction Time and Oxidation Onset Temperature measurements have been conducted to investigate the thermo-oxidative stability. Tensile tests, Dynamic Mechanical Analysis and Differential Scanning Calorimetry have been conducted on the samples in order to evaluate the effect of the additives also on the thermal and mechanical properties. Scanning Electron Microscopy have been used to assess the adhesion and distribution of the wine-wastes additives within the PP matrix. Experimental results evidence that all three wine-wastes derived additives do not significantly change the mechanical and thermal properties of PP, meanwhile they enhance its thermal stability. Moreover, the expectation to obtain better results with the commercial tannin extract has not been achieved. The obtained results show how wine wastes can be effectively used as polymer stabilizers and represent a valid alternative because of theirs environmental and cost-effects advantages.

Solution of problems of ETICS with biocorrosion

To find solutions for maintenance and repair of existing structures ETICS becomes the current another issue of improvement thermal insulation proprieties of external cladding, which need to be answered necessarily till December 2020. Double thermal insulation technology can be achieved by jointly increasing of thermal insulation properties and by repairing surface porosity ETICS. The aim of the research is the analysis of alternative insulation materials in plaster repair by technology "double thermal insulation" ETICS in terms of technology, humidity and temperature conditions in the layers. Technology of double thermal insulation is analyzed in the context with solution biocorrosion surface thermal insulation. In the end of the research there is obtained the data from the comparisson of technology double thermal insulation with different insulation materials expressed by graph. Obtained data can be the basis for decision to choosing a repair, to solution for the structural details of double thermal insulation and also for experimentally assess the lifespan of the double ETICS.

Technology of Double Thermal Insulation for the Repair and Energy Optimization of Existing Thermal Insulation Composite Systems

Abstract The theme of improvement thermal proprieties of external cladding according to the New EU Directive is still a hot topic, which needs to be answered necessarily till December 2020. Maintenance and repair of existing ETICS became to also an actual open theme in search solutions for existing constructions. The aim of the research in this review is to analyze influence of layers the alternative thermal materials in technology “double thermal insulation”. Humidity and temperature conditions will be further examined in connection with the development and colonization of microorganisms on surface construction.

Homogeneous Grafting of New Amido Groups onto Hydroxyethyl Cellulose Acetate Microfibrils: Solubility Study

Attempts to modify the surface of hydroxyethyl cellulose acetate (HECA-DS AC ~1.5) microfibrils were made using amine terminated molecules. First, the amine compounds were reacted with sebacoyl chloride in nonstoichiometry ratio in order to obtain a monoadduct chloride such as ClCO-(CH 2 ) 8 -CONHR. Then the resulted derivatives were coupled with hydrophobic hydroxyethyl cellulose acetate (HECA) by a condensation reaction in homogenous medium using triethyl amine (N(C 2 H 5 ) 3 ) in THF. The products were characterized by FTIR, 1 H NMR, 13 C NMR, and DRX, and thermal proprieties were also determined. The X-ray diffraction showed that the crystallinity of the amido esters obtained depends on both the degree of substitution and the nature of the graft moiety. The solubility study was based on the determination of the Flory–Huggins interaction parameters (χ) using the partial Hansen solubility parameters (HSP) and that were calculated from the Van Krevlen–Hoftyze (VKH) method and the T. Lindvig approximation. Keywords: cellulose; microfibrils; amidation; Hansen solubility; Flory–Huggins parameters.

Finite element modelling of the pyrolysis of wet wood subjected to fire

The modelling of the pyrolysis of wet wood provides more realistic fire scenarios for structural fire design by taking into account variable thermal properties of wood which are beyond the scope of conventional structural fire design codes. The proposed numerical methodology has been written in MATLAB environment. A 2D nonlinear finite element analysis (FEA) is performed to model the pyrolysis of wet wood subjected to high temperature. The varying of thermal proprieties of wood are discussed from the point of view of changes of structure and chemical composition under fire condition. The validity of the model is established by comparing the predicted results with results from fire resistance tests presented in literature. Qualitatively, the model provides good agreement with the experimental data. It is shown that the model can handle layers of a wooden composite structure. Temperature profiles at different points in the wood sample and the two-dimensional charring depth of Laminated Veneer Lumber (LVL) panels are calculated and compared with experimental data.