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

2021 ◽  
Vol 1203 (3) ◽  
pp. 032042
Author(s):  
Ma Ascensión Rodríguez-Esteban ◽  
Ma Soledad Camino-Olea ◽  
Alfredo Llorente-Álvarez ◽  
Alejandro Cabeza-Prieto ◽  
Ma Paz Sáez-Pérez
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Energetic Efficiency ◽  
Historic Buildings ◽  
Brick Wall ◽  
External Appearance ◽  
Hygrothermal Behavior ◽  
Technical Specifications ◽  
Historical Heritage ◽  
Different Characteristics

Abstract 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.

Hygrothermal performance of various Typha–clay composite

2018 ◽  
Vol 42 (3) ◽  
pp. 316-335 ◽  
Author(s):  
Ibrahim Niang ◽  
Chadi Maalouf ◽  
Tala Moussa ◽  
Christophe Bliard ◽  
Etienne Samin ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Optimal Composition ◽  
Volume Weight ◽  
Hygrothermal Behavior ◽  
Three Samples ◽  
Hygrothermal Performance ◽  
Absolute Density ◽  
Typha Australis ◽  
Hygric Properties ◽  
Made In

This article deals with the influence of both morphology and amount of Typha on hygrothermal behavior of a Typha–clay composite for building application. An agromaterial containing the fiber mix of Typha Australis and clay was made in three samples: three fiber mixtures were prepared with different amounts Typha and cut type (transversal or longitudinal). The physical properties of these materials were studied in terms of porosity, apparent and absolute density, thermal conductivity, and hygric properties. Results show a real impact of the Typha fraction type and its volume content on hygrothermal properties of the studied material due to the porosity. The transversal fraction of Typha (80% in volume weight) seems to be the optimal composition for a better hygrothermal behavior.

scholarly journals High-Fidelity Calculation of Effective Thermal Response of Composite Media With Heat Generation Source

2020 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Unit Cell ◽  
High Fidelity ◽  
Conductive Heat

Abstract The complexity of conductive heat transfer in a structure increases with heterogeneity (e.g., multi-component solid-phase systems with a source of internal thermal heat generation). Any discontinuity of material property — especially thermal conductivity — would warrant a thorough analysis to evaluate the thermal behavior of the system of interest. Heterogeneous thermal conditions are crucial to heat transfer in nuclear fuel assemblies, because the thermal behavior within the assemblies is governed significantly by the heterogeneous thermal conditions at both the system and component levels. A variety of materials have been used as nuclear fuels, the most conventional of which is uranium dioxide, UO2. UO2 has satisfactory chemical and irradiation tolerances in thermal reactors, whereas the low thermal conductivity of porous UO2 can prove challenging. Therefore, the feasibility of enhancing the thermal conductivity of oxide fuels by adding a high-conductivity secondary solid component is still an important ongoing topic of investigation. Undoubtedly, long-term, stable development of clean nuclear energy would depend on research and development of innovative reactor designs and fuel systems. Having a better understanding of the thermal response of the unit cell of a composite that represents a fuel matrix cell would help to develop the next generation of nuclear fuel and understand potential performance enhancements. The aim of this article is to provide an assessment of a high-fidelity computational model response of heterogeneous materials with heat generation in circular fillers. Two-dimensional, steady-state systems were defined with a circular, heat-generating filler centered in a unit-cell domain. A Fortran-based finite element method (FEM) code was used to solve the heat equation on an unstructured triangular mesh of the systems. This paper presents a study on the effects of a heat-generating filler material’s relative size and thermal conductivity on effective thermal conductance, Geff, within a heterogenous material. Code verification using the method of manufactured solution (MMS) was employed, showing a second-order accurate numerical implementation. Solution verification was performed using a global deviation grid convergence index (GCI) method to assess solution convergence and estimate solution numerical uncertainty, Unum. Trend results are presented, showing variable response in Geff to filler size and thermal conductivity.

Hygrothermal behavior for a clay brick wall

2018 ◽  
Vol 54 (6) ◽  
pp. 1579-1591 ◽  
Author(s):  
R. Allam ◽  
N. Issaadi ◽  
R. Belarbi ◽  
M. El-Meligy ◽  
A. Altahrany
Keyword(s):  
Brick Wall ◽  
Clay Brick ◽  
Hygrothermal Behavior

Thermal Performance of 3D IC Integration with Through-Silicon Via (TSV)

2011 ◽  
Vol 2011 (1) ◽  
pp. 000025-000032 ◽  
Author(s):  
Heng-Chieh Chien ◽  
John H. Lau ◽  
Yu-Lin Chao ◽  
Ra-Min Tain ◽  
Ming-Ji Dai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Thermal Performance ◽  
Equivalent Thermal Conductivity ◽  
3D Ic ◽  
Through Silicon Via

Thermal performance of 3D IC integration is investigated in this study. Emphasis is placed on the determination of a set of equivalent thermal conductivity equations for Cu-filled TSVs with various TSV diameters, TSV pitches, TSV thicknesses, passivation thicknesses, and microbump pads. Also, the thermal behavior of a TSV cell is examined. Furthermore, 3D heat transfer simulations are adopted to verify the accuracy of the equivalent equations. Finally, the feasibility of these equivalent equations is demonstrated through a simple 3D IC integration structure.

scholarly journals Nanofluid Thermal Conductivity and Effective Parameters

2018 ◽  
Vol 9 (1) ◽  
pp. 87 ◽  
Author(s):  
Sarah Simpson ◽  
Austin Schelfhout ◽  
Chris Golden ◽  
Saeid Vafaei
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nanoparticle Concentration ◽  
Effective Parameters ◽  
Conductivity Enhancement ◽  
Nanoparticle Shape ◽  
Hybrid Nanofluids ◽  
Different Characteristics ◽  
The Impact ◽  
Base Liquid

Due to the more powerful and miniaturized nature of modern devices, conventional heat-transfer working fluids are not capable of meeting the cooling needs of these systems. Therefore, it is necessary to improve the heat-transfer abilities of commonly used cooling fluids. Recently, nanoparticles with different characteristics have been introduced to base liquids to enhance the overall thermal conductivity. This paper studies the influence of various parameters, including base liquid, temperature, nanoparticle concentration, nanoparticle size, nanoparticle shape, nanoparticle material, and the addition of surfactant, on nanofluid thermal conductivity. The mechanisms of thermal conductivity enhancement by different parameters are discussed. The impact of nanoparticles on the enhanced thermal conductivity of nanofluids is clearly shown through plotting the thermal conductivities of nanofluids as a function of temperature and/or nanoparticle concentration on the same graphs as their respective base liquids. Additionally, the thermal conductivity of hybrid nanofluids, and the effects of the addition of carbon nanotubes on nanofluid thermal conductivity, are studied. Finally, modeling of nanofluid thermal conductivity is briefly reviewed.

scholarly journals Thermal Behavior of Worsted Fabrics Produced from Different Yarn Spinning Systems

2013 ◽  
Vol 8 (3) ◽  
pp. 155892501300800 ◽  
Author(s):  
Abolfazl Mirdehghan ◽  
Siamak Saharkhiz ◽  
Hooshang Nosraty
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Behavior ◽  
Thermal Insulation ◽  
Weft Yarn ◽  
Spun Yarn ◽  
Finishing Process ◽  
Yarn Structure ◽  
Fabric Structures ◽  
The Impact

This paper describes an experimental study of the impact of yarn structure on the thermal properties of worsted fabric. In this study, four different spun yarn structures (Solo, Siro, and single ply and two ply Ring) were woven into four fabric structures (Plain, Twill2/1, Twill2/2 and Basket2/2) and their thermal properties were studied. In addition, the thermal behavior of finished and unfinished samples was also evaluated. Results showed that the finishing process causes an increase in thermal conductivity and warmth to weight factor and a decrease in thermal insulation. Different spinning systems, also affect the thermal properties of the worsted fabrics. Samples with Siro yarns in the weft were found to have the highest thermal conductivity and those made from single ply weft yarn the lowest thermal conductivity. A relation between fabric thermal insulation and air permeability and thickness was also found.

Effects of Various Parameters on Nanofluid Thermal Conductivity

2006 ◽  
Vol 129 (5) ◽  
pp. 617-623 ◽  
Author(s):  
Seok Pil Jang ◽  
Stephen U. S. Choi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Volume Fraction ◽  
Heat Transfer Fluids ◽  
New Concepts ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Thermal Phenomena ◽  
First Time ◽  
Good Agreement

The addition of a small amount of nanoparticles in heat transfer fluids results in the new thermal phenomena of nanofluids (nanoparticle-fluid suspensions) reported in many investigations. However, traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain the thermal behavior of nanofluids. Recently, Jang and Choi proposed and modeled for the first time the Brownian-motion-induced nanoconvection as a key nanoscale mechanism governing the thermal behavior of nanofluids, but did not clearly explain this and other new concepts used in the model. This paper explains in detail the new concepts and simplifying assumptions and reports the effects of various parameters such as the ratio of the thermal conductivity of nanoparticles to that of a base fluid, volume fraction, nanoparticle size, and temperature on the effective thermal conductivity of nanofluids. Comparison of model predictions with published experimental data shows good agreement for nanofluids containing oxide, metallic, and carbon nanotubes.

scholarly journals Effect of Color Coating of Cover Plate on Thermal Behavior of Flat Plate Solar Collector

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6696
Author(s):  
Chengyi Li ◽  
Qunwu Huang ◽  
Yiping Wang
Keyword(s):  
Thermal Behavior ◽  
Solar Collector ◽  
Solar Irradiation ◽  
Cover Plate ◽  
Brick Wall ◽  
Absorber Plate ◽  
Plate Temperature ◽  
Glass Cover ◽  
Color Coating ◽  
The One

An important trend of Building Integrated Solar Thermal (BIST) system is to improve the aesthetic aspect of the solar collector to meet the requirement of architectural style and energy collection. Painting on the glass cover in an appropriate method is a simple and practical way. In this study, a halftone coating was used to print a red brick wall pattern on the glass cover. A series of comparative experiments were carried out to test the effect of the coating on the thermal behavior of the solar collector. In heat collection processes, compared with the solar collector with blank cover plate, the one with coated cover plate has lower absorber plate temperature and higher cover plate temperature. The lower the solar irradiance, the smaller the effect of color coating on the solar collector. Compared with the uncoated surface, the coated surface is more sensitive to solar irradiation. In the same heat collection process, compared with the solar collector coated on the outer surface of the cover plate, the one coated on the inner surface has 0.8 °C higher heat absorber plate temperature and 5% lower top heat loss.

Hybrid Thermal Behavior from Thermoelectrics to Heat Sinking of a Thin Si Membrane with Stretched Ge Quantum Dots

2010 ◽  
Vol 1267 ◽  
Author(s):  
Jean-Numa Gillet
Keyword(s):  
Thermal Conductivity ◽  
Quantum Dots ◽  
Thermal Behavior ◽  
Heat Propagation ◽  
Peltier Effect ◽  
Orthogonal Direction ◽  
Thermal Insulating ◽  
Anisotropic Thermal Conductivity ◽  
Ge Quantum Dots ◽  
Heat Sinking

AbstractA membranous nanomaterial showing, for the first time, a hybrid thermal behavior between insulating and dissipative regimes is proposed with applications in both thermoelectrics (low thermal conductivity) and passive heat sinking (high thermal conductivity). While other compounds could be chosen, the nanomaterial is made up of a thin Si membrane covered by Ge quantum dots (QDs) with epitaxial facets. The QDs are voluntarily stretched in the direction [010] or y parallel to the membrane to form elongated islands. The broken symmetry induces an exalted phonon wave-guiding in y. Therefore, when hot and cold junctions are connected to the membrane following the stretching direction [010], the anisotropic thermal conductivity shows a significant exaltation with respect to the in-plane orthogonal direction [100] or x, where the Ge islands have the smallest average size. An example nanomaterial is obtained by repetition of molecular supercell slabs containing 4348 atoms each. The thermal conductivity shows a marked exaltation higher than 22 folds, from 1.5 to 33.5 W/m/K when the connection direction between the hot and cold junctions is rotated by 90° from x to y. Therefore, the nanomaterial presents a changing thermal behavior from insulation to passive dissipation when the heat propagation direction is modified from x to y. As a result, it could be used for the design of passive heat sinkers (from the phonons) when the two junctions are connected following [010]. In contrast, a thermal insulating behavior appears when the junctions are linked following [100]. This direction can be as well used for cooling applications. However, in this case, cooling is differently generated using the Peltier effect (from the electrons). Seebeck generation can be also envisioned in the direction [100].

scholarly journals Supercritical Carbonation of Lightweight Aggregate Containing Mortar: Thermal Behavior

2014 ◽  
Vol 600 ◽  
pp. 345-356
Author(s):  
Marçal Rosas Florentino Lima Filho ◽  
Sandro Marden Torres ◽  
Leon Black ◽  
Andressa de Araújo Porto Vieira ◽  
Rodinei Medeiros Gomes ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Thermal Conductivity ◽  
Supercritical Carbon Dioxide ◽  
Thermal Behavior ◽  
Lightweight Concrete ◽  
Lightweight Aggregate ◽  
Mix Design ◽  
Lightweight Aggregates ◽  
Cylindrical Samples ◽  
Potential Use

Lightweight concrete shows good insulation properties, depending on several parameters such as mix design and aggregate type. Perlite aggregate is one of the most effective aggregates for such a purpose, mainly because of its low thermal conductivity (0.04 W/m.°C), but is not available globally. This paper explores the potential use of another source of thermal efficient aggregate, vermiculite (0.058 W/m.°C) which is available in Brazil and other countries where perlite is absent. Cylindrical samples were cast by using two lightweight aggregates, perlite and vermiculite, and treated with supercritical carbon dioxide. Supercritical carbonation (SCC) of concrete can improve mechanical, thermal and durability features. In this paper, the effect of SCC on the thermal behavior of lightweight mortars was investigated with regards to physical and microstructure features and thermal behavior due to cooling.

Sign in / Sign up

Export Citation Format

Share Document