scholarly journals Dependencies of heat transmittance through the ventilated wall system on thermal conductivity of connectors crossing thermal insulation layer

2019 ◽  
Vol 282 ◽  
pp. 02089 ◽  
Author(s):  
Aurelija Levinskytė ◽  
Raimondas Bliūdžius ◽  
Arūnas Burlingis ◽  
Tomas Makaveckas
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Thermal Insulation ◽  
Experimental Research ◽  
Experimental Studies ◽  
Insulation Material ◽  
Expanded Polystyrene Foam ◽  
Reinforced Plastic ◽  
Ventilated Facade ◽  
Wall System

The ventilated facade systems are widely used for improvement of energy efficiency and reducing of heat losses of newly built buildings and for existing buildings. To reduce the influence of point thermal bridges on heat transfer through the ventilated facades, previous often used aluminium alloy connectors as a change to stainless steel and reinforced plastic connectors. Different thermal characteristics of connectors using in ventilated facade systems, significantly influence the heat transfer coefficient of building’s walls. Previous empirical calculations of the heat transfer through ventilated facade walls with different connectors according to standard methodology and numerical modelling showed significant differences in results, therefore experimental research with the fragments of the ventilated facade systems were carried out using a guarded hotbox method. The aim of this experimental research was to analyse the heat flows through the ventilated wall system with different kind of heat-conductive connectors. Expanded polystyrene foam (λ – 0,031 W/(m∙K)) was used as thermal insulation material, thickness 300 mm, and three types of heat-conductive connections were installed: aluminum alloy (λ - 160 W/(m∙K)), stainless steel (λ - 17 W/(m∙K)) and glass fiber reinforced plastic (λ – 0,23 W/(m∙K)). The measurements in the guarded hotbox were useful for analysis of differences in results according to the standard and numerical calculations methods. The experimental studies showed that the results are very close to the numerical simulation results. The empirical calculation method gave similar results to the other two methods, except in the case of highly heat-conductive connectors.

scholarly journals Continuous, Strong, Porous Silk Firoin-Based Aerogel Fibers toward Textile Thermal Insulation

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1899 ◽  
Author(s):  
Haiwei Yang ◽  
Zongqian Wang ◽  
Zhi Liu ◽  
Huan Cheng ◽  
Changlong Li
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Hollow Fiber ◽  
High Performance ◽  
Large Scale ◽  
Low Density ◽  
Potential Candidate ◽  
Scale Production ◽  
Insulation Material ◽  
High Porosity

Aerogel fiber, with the characteristics of ultra-low density, ultra-high porosity, and high specific surface area, is the most potential candidate for manufacturing wearable thermal insulation material. However, aerogel fibers generally show weak mechanical properties and complex preparation processes. Herein, through firstly preparing a cellulose acetate/polyacrylic acid (CA/PAA) hollow fiber using coaxial wet-spinning followed by injecting the silk fibroin (SF) solution into the hollow fiber, the CA/PAA-wrapped SF aerogel fibers toward textile thermal insulation were successfully constructed after freeze-drying. The sheath (CA/PAA hollow fiber) possesses a multiscale porous structure, including micropores (11.37 ± 4.01 μm), sub-micron pores (217.47 ± 46.16 nm), as well as nanopores on the inner (44.00 ± 21.65 nm) and outer (36.43 ± 17.55 nm) surfaces, which is crucial to the formation of a SF aerogel core. Furthermore, the porous CA/PAA-wrapped SF aerogel fibers have many advantages, such as low density (0.21 g/cm3), high porosity (86%), high strength at break (2.6 ± 0.4 MPa), as well as potential continuous and large-scale production. The delicate structure of multiscale porous sheath and ultra-low-density SF aerogel core synergistically inhibit air circulation and limit convective heat transfer. Meanwhile, the high porosity of aerogel fibers weakens heat transfer and the SF aerogel cellular walls prevent infrared radiation. The results show that the mat composed of these aerogel fibers exhibits excellent thermal insulating properties with a wide working temperature from −20 to 100 °C. Therefore, this SF-based aerogel fiber can be considered as a practical option for high performance thermal insulation.

Experimental Studies and Correlations of Radially Outward and Inward Air-Flow Heat Transfer in a Rotating Square Duct

1996 ◽  
Vol 118 (1) ◽  
pp. 23-30 ◽  
Author(s):  
C. R. Kuo ◽  
G. J. Hwang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Experimental Studies ◽  
Leading Edge ◽  
Wall Heat Transfer ◽  
Square Duct ◽  
Reinforced Plastic ◽  
Flow Heat ◽  
The Mean ◽  
Heated Length

Experiments were conducted to investigate the convective heat transfer of radially outward and inward air flows in a uniformly heated rotating square duct. The interior duct surfaces, constructed by fiberglass-reinforced plastic, were plated with separated film heaters for distinguishing the local wall heat transfer rate. The duct hydraulic diameter, the actively heated length, and the mean rotation radius are 4, 120, and 180 mm, respectively. In the experiments, the parameters were the throughflow Reynolds number, Re = 1,000∼15,000; the rotation number, Ro = 0∼0.32; and the rotational buoyancy parameter, Ra* = 0∼0.5. For the outward flow the Coriolis-induced cross-stream secondary flow strongly enhanced the heat transfer on the leading edge. But for the radially inward flow the trend was reversed. When the throughflow Reynolds number was increased, the rotating-buoyancy decreased, then increased the heat transfer for the outward flow; however, the rotating-buoyancy always increased the heat transfer for the inward flow. The heat transfer data are correlated for the outward and inward flows for the ranges of parameters under study.

scholarly journals To the determination of heat exchange conditions near the inner surface of walls with reflective thermal insulation from aluminium foil

2018 ◽  
Vol 196 ◽  
pp. 02035 ◽  
Author(s):  
Nina Umnyakova ◽  
Mikhail Gandzhuntsev
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Experimental Studies ◽  
Building Envelope ◽  
Surface Radiation ◽  
Thermal Engineering ◽  
Transfer Coefficients ◽  
Concrete Wall ◽  
Heat Transfer Coefficients ◽  
Inner Surface

Materials with a low coefficient of surface radiation intensively reflect the radiant component of the heat flux and reduce heat losses through the building envelope. When designing building structures with reflective thermal insulation it is necessary to evaluate the efficiency of its application. However, at present there are no methods for calculating the value of thermal losses through external walls in the presence of reflective thermal insulation on internal surface of the wall, as well as there are no data on the values of heat transfer coefficients at the inner surface of building envelope with reflective thermal insulation. In this regard, in the climatic chambers of NIISF RAABS, complex thermal engineering studies were carried out. For this a cellular concrete wall 2,8 x1,2 m was put up into the chamber with reflective thermal insulation on the inner surface and without it. The obtained results of experimental studies, presented in the work, allowed obtaining numerical values of heat transfer coefficients at the inner surface of walls with reflective thermal insulation, and use the obtained data in further calculations.

Experimental Investigation on the Thermal Insulation Properties of Eic-Cellulose

2014 ◽  
Vol 554 ◽  
pp. 322-326 ◽  
Author(s):  
Wuryanti Sri ◽  
Suhardjo Poertadji ◽  
Bambang Soegijono ◽  
Nasution Henry
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Thermal Insulation ◽  
Cellulose Fibers ◽  
Extraction Process ◽  
Thermal Capacity ◽  
Insulation Material ◽  
Low Thermal Conductivity ◽  
Thermal Conductivities

The material with low thermal conductivity means it has a high insulating capability for reducing heat transfer. One of materials for insulation is cellulose. This study presents a insulation material of cellulose made from reeds imperata cylindrical type with the extraction process. The extraction of cellulose fibers to form a sheet by adding 3.5% Na-CMC (Sodium Cellulose Carboksil Metyl). The process of forming the sheet uses blender for 30 minutes, 45 minutes, and 60 minutes. Furthermore, each mixture are put into the oven with temperature of 40°C for 36 hours. There are three parameters will be investigated, i.e. thermal conductivity, density and thermal capacity. The results showed that the lowest and the highest of thermal conductivities were 0.22 W/m K and a maximum 0.36 W/m K, respectively.

scholarly journals Effects of diagonal bracing on thermal insulation of wood-frame walls

BioResources ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 517-528
Author(s):  
Mingbin Liu ◽  
Feng Lu ◽  
Xuedong Zhang ◽  
Xiaolin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Insulation ◽  
Expanded Polystyrene ◽  
Polystyrene Foam ◽  
Expanded Polystyrene Foam ◽  
Cold Area ◽  
Wood Frame ◽  
The Heat Transfer Coefficient

The influence of various diagonal-bracings arrangements on the heat transfer coefficient of wooden walls was studied with the goal of improving the thermal insulation performance of the walls. Through the reliability verification of the theoretical value of the heat transfer coefficient, this study found that a larger proportion of wood frame area resulted in larger theoretical and test values for the heat transfer coefficient. The heat transfer coefficient of the wall with expanded polystyrene foam sheet (EPS) was 5.90% to 6.10% higher than that with extruded polystyrene foam sheet (XPS), and the tested value was 4.75% to 8.60% higher. The maximum value of the average heat transfer coefficient of 12 diagonal-braced walls was 0.366 W·m-2·K-1, which met the thermal level of the severe cold area. The test value of the heat transfer coefficient was larger than the theoretically calculated value, and the linear correlation was up to 0.978.

Research on Heat Transfer Properties and Insulation Mechanism of FHP-Vc Inorganic Composite Silicate Insulation Board

2012 ◽  
Vol 550-553 ◽  
pp. 2791-2796
Author(s):  
Ling Zeng ◽  
Yan Shao ◽  
Hui Zuo ◽  
Jia Hua Li
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Building Energy ◽  
Building Energy Efficiency ◽  
Insulation Material ◽  
Thermal Insulation Material ◽  
Current Design ◽  
Building Energy Saving ◽  
Transfer Properties ◽  
Inorganic Composite

The paper introduced the basic performance and thermal insulation mechanism of a new building thermal insulation material—FHP-Vc inorganic composite silicate heat-insulating board which is used as the thermal insulation material for exterior wall. Based on the experiments and analysis of the heat transfer performance of FHP-Vc board, it has been found that the thermal performance of FHP-Vc board meets the current design standard of building energy efficiency. At the same time, it is a new building energy-saving material which has good insulation, non-burning, reliable and economical properties.

scholarly journals Theoretical and experimental studies of effective thermal insulation in the production, storage and transportation of agricultural products

2020 ◽  
Vol 175 ◽  
pp. 11013
Author(s):  
Mikhail Lemeshko ◽  
Snanislav Maslennikov ◽  
Sergey Bashnyak ◽  
Irina Kokunko
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Insulation ◽  
New Technology ◽  
Experimental Studies ◽  
Sandwich Panels ◽  
Agricultural Products ◽  
The Cost ◽  
The Heat Transfer Coefficient ◽  
Very High

The article presents the results of research on a new technology for increasing the thermal insulation properties of fences based on sandwich panels for thermal insulation of buildings, storage facilities, cooling chambers, industrial and residential premises, as well as for the production, storage and transportation of agricultural products. The costs of cold and heat are reflected in the cost of agricultural products. The idea is to replace the air in the pores of mineral (basalt) wool with gas with low thermal conductivity. The article presents a theoretical analysis of the possible effectiveness of this substitution, and the developed research methodology. The analysis made it possible to predict a possible decrease in the heat transfer coefficient by about 21%. This is a very high indicator. It can be assumed that approximately this value can reduce the cost of electricity spent on maintaining rational temperatures. The scheme and description of the stand for experimental research, and the results of these studies are given. It was found that as a result of the conducted experiments, it was possible to obtain a decrease in the thermal conductivity of sandwich panels with argon by 8.8%, and with carbon dioxide by 10.2%.

scholarly journals Assessment of the influence of the structural characteristics of granular systems of microsilicon on the properties of thermal insulation materials

2022 ◽  
Vol 320 (1) ◽  
pp. 5-14
Author(s):  
I.B. Sangulova ◽  
◽  
V.P. Selyaev ◽  
E.I. Kuldeev ◽  
R.E. Nurlybaev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Granular Materials ◽  
Thermal Insulation ◽  
Structural Characteristics ◽  
Particle Surface ◽  
Experimental Studies ◽  
Granular Systems ◽  
Scattering Method ◽  
Gas Molecules

The article discusses experimental studies of the size and shape of structured particles of microsilica small angle x-ray scattering method and a photophonon theoretical description of the heat transfer process in complex heterogeneous structures to assessment of the structural characteristics of granular systems for the properties of thermal insulating materials. The mechanism of heat transfer in granular, porous systems is quite complex, since heat exchange occurs in a material consisting of two phases (solid and gas) and at the phase boundary. Heat transfer in liquid thermal insulation coatings can be carried out from one solid particle to another. In this case, the thermal conductivity will depend on: the chemical and elemental composition of the material; particle granulometry; surface topology - the presence of inhomogeneities, defects on the surface; the number of touches and the contact area between the particles. The heat transfer of gas in the pores is carried out when gas molecules collide. Thermal conductivity will be determined by the ratio of the free path of molecules and linear pore sizes, temperature and dynamic viscosity of the gas phase, the nature of the interaction of gas molecules with the solid phase. Heat transfer by radiation depends on the nature of the particles, the dielectric, magnetic permeability and the degree of blackness of the particle surface. Based on the analysis of possible mechanisms of heat transfer in granular systems, it can be argued that the effective thermal conductivity of the system depends, all other things being equal, on the structure of the pore space of granular materials, topology and the number of particle touches. Considering idealized models of the structure of granular materials in the form of ordered folds of perfectly smooth balls, we can obtain several variants of structures: with tetrahedral; hexagonal; cubic packing of balls.

scholarly journals The influence of polyisocyanurate (PIR) facing on the heat transfer through the corners of insulated building partitions

2020 ◽  
Vol 172 ◽  
pp. 08008
Author(s):  
Tomas Makaveckas ◽  
Raimondas Bliūdžius
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Thermal Insulation ◽  
Insulation Material ◽  
Transfer Coefficients ◽  
Thermal Insulation Material ◽  
Heat Transfer Coefficients ◽  
Thermal Bridge ◽  
The Stability ◽  
Structural Solutions

Prefabricated products made of polyisocyanurate (PIR) thermal insulation material covered with cardboard, plastic, aluminium or composite facings are used for thermal insulation of building envelopes. The facing of these products is selected according to their conditions of use, and the effect of the facing on the declared thermal properties of the product depend only on water vapor diffuse properties of the facing. However, at the corners of the building where these products are joined, facings can be in the direction of the heat flux movement and significantly increase heat transfer through the longitudinal thermal bridge formed in the corner of the building. After analysing the solutions for installation of PIR thermal insulation products on the walls and roof corners of buildings, calculations of the heat transfer coefficients of the linear thermal bridges were made, and the influence of various facings and different structural solutions on the heat transfer coefficient value of the thermal bridge was determined. Aluminium foil facing have the greatest influence, but other facings must also be considered. The structural solutions with the greatest increase in the heat transfer due to the effect of the facing were selected, and the influence to the thermal and air tightness properties of the structural solution when facing is removed were analysed, the stability of thermal properties of the thermal insulation material were analysed as well. Proposals for joining PIR thermal insulation products with heat-conductive facings in the corners of buildings were prepared.

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