Modeling of Heat Transfer in Low-Density EPS Foams

2005 ◽  
Vol 128 (6) ◽  
pp. 538-549 ◽  
Author(s):  
R. Coquard ◽  
D. Baillis
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Structural Characteristics ◽  
Expanded Polystyrene ◽  
Radiative Properties ◽  
Cell Diameter ◽  
Low Density ◽  
Equivalent Thermal Conductivity ◽  
Numerical Resolution ◽  
Steady State Heat Transfer

Expanded polystyrene (EPS) foams are one of the most widely used thermal insulators in the building industry. Owing to their very low density, both conductive and radiative heat transfers are significant. However, only few studies have already been conducted in the modeling of heat transfer in this kind of medium. This is due to their complex porous structure characterized by a double-scale porosity which has always been ignored by the previous works. In this study, we present a model of one-dimensional steady state heat transfer in these foams based on a numerical resolution of the radiation-conduction coupling. The modeling of the conductive and radiative properties of the foams takes into account their structural characteristics such as foam density or cell diameter and permits us to study the evolution of their equivalent thermal conductivity with these characteristics. The theoretical results have been compared to equivalent thermal conductivity measurements made on several EPS foams using a flux-meter apparatus and show a good agreement.

Conductive and Radiative Heat Transfer in Foam Materials at High Temperatures

2013 ◽  
Vol 431 ◽  
pp. 192-197
Author(s):  
J.E. Li ◽  
B. Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
High Temperatures ◽  
Cell Model ◽  
The Body ◽  
Radiative Properties ◽  
Solid Matrix ◽  
Cell Diameter ◽  
Equivalent Thermal Conductivity ◽  
Effects Of Temperature

At high temperatures, heat transfer in foams occurs by conductions through solid matrix and air as well as by thermal radiation propagating the structure. Starting from the analysis of different foam morphological structures, the body-centered cubic cell model is applied to predict the conductive and radiative properties. Both the open foams and the closed foams are analyzed. Temperature-dependency of the material properties is also taken into consideration. The Rosseland approximation is used to predict the radiativie conductivity. Effects of temperature, cell diameter and porosity on the equivalent thermal conductivity are discussed. It is found that both the temperature and the structure parameters have strong influences on the equivalent thermal conductivity.

Radiative Properties of Expanded Polystyrene Foams

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Coquard Rémi ◽  
Baillis Dominique ◽  
Quenard Daniel
Keyword(s):  
Heat Transfer ◽  
Structural Parameters ◽  
Expanded Polystyrene ◽  
Radiative Properties ◽  
Low Density ◽  
Complex Morphology ◽  
Hemispherical Reflectance ◽  
Good Accordance ◽  
Porous Morphology ◽  
Thick Material

Expanded polystyrene foams are one of the most widely used materials for a building’s thermal insulation. Owing to their very low density, a substantial proportion of the heat transfer is due to thermal radiation propagating through their porous structure. In order to envisage an optimization of their thermal performances, an accurate modeling of their radiative behavior is required. However, the previous studies on this subject used several drastic simplifications regarding their radiative behavior (optically thick material) or their porous morphology (homogeneous cellular material, dodecahedral cells). In this study, we propose a more accurate model based on a detailed representation of their complex morphology allowing us to predict their entire monochromatic radiative properties. We investigated the influence of the different structural parameters on these properties. We checked the validity of our model by comparing the spectral hemispherical reflectance and transmittance measured on slabs of foam samples with values predicted by our model. A good accordance was found globally.

scholarly journals Influence of Surface Emissivity and of Low Emissivity Shields on the Thermal Properties of Low Density Insulating Materials

2011 ◽  
Author(s):  
Mariacarla Arduini ◽  
Manuela Campanale ◽  
Lorenzo Moro
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Test Temperature ◽  
Transfer Factor ◽  
Thermal Characteristics ◽  
Expanded Polystyrene ◽  
Low Density ◽  
Insulating Materials ◽  
Insulating Material ◽  
Radiation Extinction

The theory of heat transfer through low density insulating materials explains the importance of thermal radiation in the overall heat transfer. As a matter of fact, in many semitransparent insulating materials, radiation has a considerable influence on measured thermal conductivity. In this work we continue the investigation (both experimentally and theoretically) on the heat transfer through low density insulating materials that we started some years ago and whose results have been presented in some International Conferences. Test have been done on low density insulating materials: expanded polystyrene with a density of 10 kg/m3 and polyester fibres with a density of 9 kg/m3 (these last tests are not yet completed and will not be discussed in this paper). The transfer factor T was measured in the heat flow meter apparatus of our laboratory [1]. The first measurements have been done with the two surfaces of the apparatus uncoated (emissivity ε = 0.91) at a mean test temperature of 283 K (10 °C) and then with the specimens enclosed in the aluminium foils (emissivity ε = 0.045) at the same mean test temperature. The results obtained from the measurements of the transfer factor T pointed out that a change of the emissivity ε of the surfaces from 0.91 to 0.045 caused a considerable decreasing of the transfer factor. Then the same panels have been cut into two slices and the aluminium foil has been interposed also between the slices, as shield, and the transfer factor was measured again in both cases: at first with the surfaces of the apparatus uncoated and then with the surfaces of the apparatus coated with the aluminium foils. In both cases the decreasing of the transfer factor τ was not negligible. The radiation extinction parameters have been then measured with a spectrometer and a model has been found to predict the transfer factor T in function of the testing conditions. We can conclude that in presence of a thin reflective metal cover placed on a low density insulating material, the thermal conductivity decrease immediately (about 7%) with a significant improvement of the thermal characteristics of the insulating material. If we put then some low emissivity foils between the slices of the material, another considerable decreasing of the thermal conductivity can be obtained (about 10%) and in presence of both aluminum foils (inside and outside). This fact confirms the importance of the contribution of radiation in thermal transmissivity of low density insulating materials and gives the possibility to reduce and to predict the thermal performances of such a material.

scholarly journals Evaluation model of the steady-state heat transfer performance of two-phase closed thermosyphons

2021 ◽  
pp. 166-166
Author(s):  
Yafeng Wu ◽  
Zhe Zhang ◽  
Wenbin Li ◽  
Daochun Xu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Two Phase ◽  
Equivalent Thermal Conductivity ◽  
State Heat ◽  
Steady State Heat ◽  
Steady State Heat Transfer

Two-phase closed thermosyphons have good thermal conductivity and are widely used in heat transfer applications. It is essential to establish an effective method for evaluating the steady-state heat transfer performance of two-phase closed thermosyphons, as such a method can help to select appropriate designs and to improve the efficiency of these devices. In this paper, the equivalent thermal conductivity is derived by the principle of equal total thermal resistance, in which the influence of the adiabatic length is eliminated. An evaluation model of the steady-state heat transfer performance of two-phase closed thermosyphons is established. Test results of three two-phase closed thermosyphons with total lengths of 220 mm, 320 mm and 500 mm show that as the heat transfer rate increases, the equivalent thermal conductivity of these devices decreases by 28.91%, increases by 6.10% and increases by 10.02%, respectively, among which the minimum value is 831.63 W?m-1?K-1and the maximum value is 1694.19 W?m-1?K-1. The decrease (increase) in the equivalent thermal conductivity in the evaluation model indicates a decrease (increase) in the heat transfer performance. The results show that the equivalent thermal conductivity of the model can effectively evaluate the heat transfer performance of two-phase closed thermosyphons.

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 Change in Conductive–Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation—Experimental and Simulated Investigations

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2626
Author(s):  
Aurelia Blazejczyk ◽  
Cezariusz Jastrzebski ◽  
Michał Wierzbicki
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Insulation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Expanded Polystyrene ◽  
Transfer Mechanism ◽  
Total Thermal Conductivity ◽  
Heat Transfer Mechanism

This article introduces an innovative approach to the investigation of the conductive–radiative heat transfer mechanism in expanded polystyrene (EPS) thermal insulation at negligible convection. Closed-cell EPS foam (bulk density 14–17 kg·m−3) in the form of panels (of thickness 0.02–0.18 m) was tested with 1–15 µm graphite microparticles (GMP) at two different industrial concentrations (up to 4.3% of the EPS mass). A heat flow meter (HFM) was found to be precise enough to observe all thermal effects under study: the dependence of the total thermal conductivity on thickness, density, and GMP content, as well as the thermal resistance relative gain. An alternative explanation of the total thermal conductivity “thickness effect” is proposed. The conductive–radiative components of the total thermal conductivity were separated, by comparing measured (with and without Al-foil) and simulated (i.e., calculated based on data reported in the literature) results. This helps to elucidate why a small addition of GMP (below 4.3%) forces such an evident drop in total thermal conductivity, down to 0.03 W·m−1·K−1. As proposed, a physical cause is related to the change in mechanism of the heat transfer by conduction and radiation. The main accomplishment is discovering that the change forced by GMP in the polymer matrix thermal conduction may dominate the radiation change. Hence, the matrix conduction component change is considered to be the major cause of the observed drop in total thermal conductivity of EPS insulation. At the microscopic level of the molecules or chains (e.g., in polymers), significant differences observed in the intensity of Raman spectra and in the glass transition temperature increase on differential scanning calorimetry(DSC) thermograms, when comparing EPS foam with and without GMP, complementarily support the above statement. An additional practical achievement is finding the maximum thickness at which one may reduce the “grey” EPS insulating layer, with respect to “dotted” EPS at a required level of thermal resistance. In the case of the thickest (0.30 m) panels for a passive building, above 18% of thickness reduction is found to be possible.

scholarly journals Heat Transfer Dynamic Analyses for Recycled-Concrete Wall Combined with Expanded Polystyrene Template

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Jianhua Li ◽  
Wenjing Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Calculation Method ◽  
Research Work ◽  
Shear Wall ◽  
Climatic Conditions ◽  
Expanded Polystyrene ◽  
Recycled Concrete ◽  
Concrete Wall ◽  
Ordinary Concrete

Due to the benefits of pollution reduction, energy saving, and recycling of resources associated with the recycled concrete, together with the apparent thermal storage thermal insulation yield of expandable polystyrene (EPS) template, the heat transfer dynamics of their combination has become a contemporary study topic. In this research work, an investigation of the heat transfer coefficient (U) of EPS template recycled-concrete shear wall has been carried out. Four different concrete mixtures shear wall samples having different insulation types were developed for the purpose of quantifying their thermal outputs. Both temperature (T) and humidity (H) affection to thermal conductivity coefficient (λ) of reinforced concrete and the EPS template were investigated, correspondingly. The λ0°C (relative variation for a 0°C of temperature variation in T) of cement mortar, recycled-concrete shear wall, and ordinary concrete shear wall were measured being 0.7526, 1.2463, and 1.3750 W·m−1·K−1, respectively. And the λ calculation of EPS was carried out being 0.0396 W·m−1·K−1. A corrected calculation method was put forward to application in practical work that could reflect the real U value in a more precise manner. These results brought to light the fact that the heat preservation output of recycled-concrete shear wall posed to be comparatively more improved than that of ordinary concrete shear wall. We put forth the suggestion for the use of corrected calculation method in the calculation and analysis of U of EPS template recycled-concrete composite shear wall in the climatic conditions of Beijing. The results revealed the fact that the U of EPS template recycled-concrete shear wall was dominantly controlled by the change of thermal conductivity changes of EPS template. The monthly mean U increased with increasing Tout and decreased with decreasing Tout. The smaller the U of the enclosure wall was, the better the thermal stability of the wall was experienced.

scholarly journals STEADY-STATE HEAT TRANSFER IN A PLATE WITH TEMPERATURE-DEPENDENT THERMAL CONDUCTIVITY (AN EXACT SOLUTION)

2019 ◽  
Vol 18 (2) ◽  
pp. 85
Author(s):  
A. Miguelis ◽  
R. Pazetto ◽  
R. M. S. Gama
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Transfer Problem ◽  
Internal Heat ◽  
Temperature Dependent ◽  
State Heat ◽  
Kirchhoff Transformation ◽  
Steady State Heat ◽  
Steady State Heat Transfer

This work presents the solution of the steady-state heat transfer problem in a rectangular plate with an internal heat source in a context in which the thermal conductivity depends on the local temperature. This generalization of one of the most classical heat transfer problems is carried out with the aid of the Kirchhoff transformation and employs only well known tools, as the superposition of solutions and the Fourier series. The obtained results illustrate how the usual procedures may be extended for solving more realistic physical problems (since the thermal conductivity of any material is temperature-dependent). A general formula for evaluating the Kirchhoff transformation as well as its inverse is presented too. This work has a strong didactical contribution since such analytical solutions are not found in any classical heat transfer book. In addition, the main idea can be used in a lot of similar problems.

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