A procedure to determine the design value of thermal conductivity of thermal insulation materials

Natural fibres from flax and hemp are used as raw materials for efficient thermal insulation. In current work, tests were carried out using chopped and combed long flax fibres as well as chopped and combed long hemp fibres. Investigations have shown that thermal conductivity of natural fibres depends on their preparation method (combing, chopping) and materials density.

Download Full-text

Rigid Polyurethane Foams Modified with Biochar

Materials ◽

10.3390/ma14195616 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5616

Author(s):

Katarzyna Uram ◽

Maria Kurańska ◽

Jacek Andrzejewski ◽

Aleksander Prociak

Keyword(s):

Thermal Conductivity ◽

Thermal Stability ◽

Thermal Insulation ◽

Foam Cells ◽

Polyurethane Foams ◽

Cross Sectional ◽

Rigid Polyurethane Foams ◽

Insulation Materials

This paper presents results of research on the preparation of biochar-modified rigid polyurethane foams that could be successfully used as thermal insulation materials. The biochar was introduced into polyurethane systems in an amount of up to 20 wt.%. As a result, foam cells became elongated in the direction of foam growth and their cross-sectional areas decreased. The filler-containing systems exhibited a reduction in their apparent densities of up to 20% compared to the unfilled system while maintaining a thermal conductivity of 25 mW/m·K. Biochar in rigid polyurethane foams improved their dimensional and thermal stability.

Download Full-text

Glass-Oxide Nanocomposites as Effective Thermal Insulation Materials

MRS Proceedings ◽

10.1557/opl.2013.1191 ◽

2013 ◽

Vol 1558 ◽

Cited By ~ 1

Author(s):

Qing Hao ◽

Minqing Li ◽

Garrett Joseph Coleman ◽

Qiang Li ◽

Pierre Lucas

Keyword(s):

Thermal Conductivity ◽

Thermal Insulation ◽

Room Temperature ◽

Phonon Scattering ◽

Material Composition ◽

Insulation Materials ◽

Atomic Structures ◽

Porous Nanocomposites ◽

Theoretical Minimum

ABSTRACTWith extremely disordered atomic structures, a glass possesses a thermal conductivity k that approaches the theoretical minimum of its composition, known as the Einstein’s limit.1 Depending on the material composition and the extent of disorder, the thermal conductivity of some glasses can be down to 0.1-0.3 W/m∙K at room temperature,2,3 representing some of the lowest k values among existing solids. Such a low k can be further reduced by the interfacial phonon scattering within a nanocomposite that can be used for thermal insulation applications. In this work, nanocomposites hot pressed from the mixture of glass nanopowder (GeSe4 or Ge20Te70Se10) and commercial SiO2 nanoparticles, or pure glass nanopowder, are investigated for the potential k reduction. It is found that adding SiO2 nanoparticles will instead increase k if the measured k values for usually porous nanocomposites are converted into those for the corresponding solid (kSolid) with Eucken’s formula. In contrast, pure glass nano-samples always show kSolid data significantly reduced from that for the starting glass. For a pure GeSe4 nano-sample, kSolid would beat the Einstein’s limit for its composition.

Download Full-text

Effects of boric acid addition and sintering temperature on the thermal conductivity of perlitebased insulation materials

Materials Testing ◽

10.1515/mt-2020-620413 ◽

2020 ◽

Vol 62 (4) ◽

pp. 408-412

Author(s):

Yuksel Palaci

Keyword(s):

Thermal Conductivity ◽

Physical Properties ◽

Boric Acid ◽

Thermal Insulation ◽

Sintering Temperature ◽

Direct Relation ◽

Insulation Materials ◽

Acid Addition ◽

Composition Characteristics

Abstract In this study, the variation of thermal conductivity and density of 15 wt.-% boric acid - 85 wt.-% sepiolite, 30 wt.-% boric acid - 30 wt.-% sepiolite - 40 wt.-% perlite, 30 wt.-% boric acid - 30 wt.-% cordierite - 40 wt.-% perlite and 30 wt.-% boric acid - 30 wt.-% alumina - 40 wt.-% perlite compositions at 700 °C and 900 °C sintering temperatures were investigated. The results show that increasing the amount of boric acid and decreasing the sintering temperature lead to an improvement in thermal insulation properties. There is a direct relation between the thermal conductivity and density of the specimens. Both physical properties change with a change in the sintering temperature and the composition characteristics. Minimum thermal conductivity has been observed in a specimen consisting of 30 wt.-% boric acid - 30 wt.-% alumina - 40 wt.-% perlite.

Download Full-text

Effect of Operating Temperatures on Thermal Conductivity of Polystyrene Insulation Material: Impact on Envelope-Induced Cooling Load

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.564.315 ◽

2014 ◽

Vol 564 ◽

pp. 315-320 ◽

Cited By ~ 8

Author(s):

Maatouk Khoukhi ◽

Mahmoud Tahat

Keyword(s):

Thermal Conductivity ◽

Thermal Insulation ◽

Energy Performance ◽

Building Envelope ◽

Insulation Material ◽

Cooling Load ◽

Thermal Insulation Material ◽

Insulation Materials ◽

Energy Performance Of Buildings ◽

The Impact

The impact of the thermal conductivity (k-value) change of polystyrene insulation material in building envelope due to changes in temperature on the thermal and energy performance of a typical residential building under hot climate is investigated. Indeed, the thermal and energy performance of buildings depends on the thermal characteristics of the building envelope, and particularly on the thermal resistance of the insulation material used. The thermal insulation material which is determined by its thermal conductivity, which describes the ability of heat to flow cross the material in presence of a gradient of temperature, is the main key to assess the performance of the thermal insulation material. When performing the energy analysis or calculating the cooling load for buildings, we use published values of thermal conductivity of insulation materials, which are normally evaluated at 24°C according to the ASTM standards. In reality, thermal insulation in building is exposed to significant and continuous temperature variations, due essentially to the change of outdoor air temperature and solar radiation. Many types of insulation materials are produced and used in Oman, but not enough information is available to evaluate their performance under the prevailing climatic condition. The main objective of this study is to investigate the relationship between the temperature and thermal conductivity of various densities of polystyrene, which is widely used as building insulation material in Oman. Moreover, the impact of thermal conductivity variation with temperature on the envelope-induced cooling load for a simple building model is discussed. This work will serve as a platform to investigate the effect of the operating temperature on thermal conductivity of other building material insulations, and leads to more accurate assessment of the thermal and energy performance of buildings in Oman.

Download Full-text

Prospects for the Application of Wavelet Analysis to the Results of Thermal Conductivity Express Control of Thermal Insulation Materials

Energies ◽

10.3390/en14175223 ◽

2021 ◽

Vol 14 (17) ◽

pp. 5223

Author(s):

Oleksandra Hotra ◽

Svitlana Kovtun ◽

Oleg Dekusha ◽

Żaklin Grądz

Keyword(s):

Thermal Conductivity ◽

Wavelet Transform ◽

Data Processing ◽

Thermal Insulation ◽

Control Method ◽

Measurement Data ◽

Conductivity Measurement ◽

Differential Method ◽

Expanded Polystyrene ◽

Insulation Materials

This article discusses an express control method that allows in situ measurements of the thermal conductivity of insulation materials. Three samples of the most common thermal insulation materials, such as polyurethane, extruded polystyrene, and expanded polystyrene, were studied. Additionally, optical and organic glasses were investigated as materials with a stable value of thermal conductivity. For the measurement of thermal conductivity, the express control device, which implements the differential method of local heat influence, was used. The case studies were focused on the reduction of fluctuations of the measured signals caused by different influencing factors using wavelet transform. The application of wavelet transform for data processing decreased the thermal conductivity measurement’s relative error for organic glass SOL and optical glasses TF-1 and LK-5. The application of wavelet transform thermal conductivity measurement data for polyurethane, extruded polystyrene, and expanded polystyrene allowed to reduce twice the duration of express control while maintaining the same level of measurement error. The results of the investigation could be used to increase the accuracy in express control of the thermal conductivity of insulation materials by improving the data processing. This approach could be implemented in software and does not require a change in the design of the measuring equipment or the use of additional tools.

Download Full-text

The effect of heat treatment on thermal conductivity of paulownia wood

European Journal of Wood and Wood Products ◽

10.1007/s00107-019-01470-3 ◽

2019 ◽

Vol 78 (1) ◽

pp. 205-207

Author(s):

Z. Pásztory ◽

S. Fehér ◽

Z. Börcsök

Keyword(s):

Thermal Conductivity ◽

Heat Treatment ◽

Thermal Treatment ◽

Thermal Insulation ◽

Insulation Materials ◽

Heat Treated ◽

Paulownia Wood

AbstractThe thermal conductivity properties of wood of Paulownia Clones in Vitro 112 were investigated after heat treatment at temperatures of 180 °C, 200 °C and 220 °C. After the treatment, the density decreased by 5.6, 8.9, and 14.1% for the samples heat-treated at 180 °C, 200 °C and 220 °C, respectively. The decrease in the thermal conductivity was 0, 2.6 and 15.7%, respectively. The thermal conductivity of kiri wood after thermal treatment at 220 °C was 0.064 W/mK, which is almost the same as that of thermal insulation materials.

Download Full-text

Changes in the Time of Thermal Conductivity of Gas-Filled Polymer Thermal Insulation Materials

Stroitel nye Materialy ◽

10.31659/0585-430x-2017-749-6-28-31 ◽

2017 ◽

Vol 749 (6) ◽

pp. 28-31

Author(s):

V.G. GAGARIN ◽

◽

P.P. PASTUSHKOV ◽

Keyword(s):

Thermal Conductivity ◽

Thermal Insulation ◽

Filled Polymer ◽

Insulation Materials

Download Full-text

Possibilities of Using Natural Fibres for Production of Particular Insulation for Use in Civil Engineering

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1124.111 ◽

2015 ◽

Vol 1124 ◽

pp. 111-116

Author(s):

Martina Reif ◽

Jitka Peterková ◽

Jiri Zach

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Thermal Insulation ◽

Civil Engineering ◽

Research Work ◽

Natural Fibers ◽

Cellulose Fibers ◽

Natural Fibres ◽

Insulation Materials ◽

Bast Fibers

The paper deals with the development options of particular insulation based on a blend of recycled cellulose fibers and natural (mainly) bast fibers. The paper presents the results of research work in the field of addiction thermal insulation, acoustic and mechanical properties of experimentally produced insulators on density..Keywords: Natural fibers, thermal conductivity, insulation materials, straw, fibreboard, cellulose fibers

Download Full-text

Investigation of the Thermal Conductivity of Resin-Based Lightweight Composites Filled with Hollow Glass Microspheres

Polymers ◽

10.3390/polym12030518 ◽

2020 ◽

Vol 12 (3) ◽

pp. 518 ◽

Cited By ~ 1

Author(s):

Zhipeng Xing ◽

Hongjun Ke ◽

Xiaodong Wang ◽

Ting Zheng ◽

Yingjie Qiao ◽

...

Keyword(s):

Thermal Conductivity ◽

Prediction Model ◽

Thermal Insulation ◽

Hollow Glass Microspheres ◽

Insulation Materials ◽

Three Phase ◽

Oil Pipelines ◽

Thermal Conductivity Model ◽

Phase Prediction ◽

Offshore Oil

The design and development of thermal insulation materials is very important for the treatment of offshore oil pipelines. Understanding thermal energy transport in thermal insulation materials and predicting their thermal conductivities have important theoretical and practical value for the design of thermal insulation materials. In this work, lightweight and thermally insulated (LWTI) composites with the desired mechanical strength for offshore oil pipelines applications were prepared using epoxy resin (EP) as the matrix and hollow glass microspheres (HGMs) as the filler. The morphology, density, and mechanical properties of HGM/EP LWTI composites were studied first. The flexural strength and the flexural modulus of HGM/EP LWTI composites could still be as high as 22.34 ± 2.75 Mpa and 1.34 ± 0.03 GPa, respectively, while the density was only 0.591 g/cm3. The relationship between the effective thermal conductivity of HGM/EP LWTI composites and material parameters (sizes and contents together) has been studied systematically. A three-phase prediction model was built using the self-consistent approximation method to predict the effective thermal conductivity of HGM/EP LWTI composites, and the resin matrix, the wall thickness, the HGM particle size, and other parameters (such as air) were fully considered during the derivation of this three-phase thermal conductivity model. Finally, the insulation mechanism of HGM/EP LWTI composites was systematically analyzed. The thermal conductivities of HGM/EP LWTI composites with different diameters and HGM contents calculated by the three-phase prediction model agreed well with the experimental test results, with a minimum error of only 0.69%. Thus, this three-phase thermal conductivity model can be used to theoretically simulate the thermal conductivity of epoxy resin-based LWTI composites and can be the theoretical basis for the design and prediction of the thermal conductivity of other similar hollow spheres filled materials.

Download Full-text