scholarly journals The influence of climatic conditions on the thermal state of frame partitions insulated with loose fiber materials

2019 ◽  
Vol 282 ◽  
pp. 02038
Author(s):  
Piotr Kosiński ◽  
Aneta Skoratko
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Building Materials ◽  
Thermal State ◽  
Operating Temperature ◽  
Climatic Conditions ◽  
Laboratory Results ◽  
Simulation Results ◽  
Fiber Materials

The paper focus of the influence of the climatic conditions on thermal state and heat transfer of the frame partitions insulated with loose wood wool. While it is well known that building materials change thermal conductivity depending on the operating temperature, the always question is how much it influences on the whole element. The paper presents the laboratory results from the hot box chamber investigation of the frame partition. These results are compared with the simulation results.

scholarly journals The Non-Stationary Thermal Mode for Barrier Building Constructions in Non-Symmetric Boundary Conditions

2018 ◽  
Vol 7 (3.2) ◽  
pp. 535
Author(s):  
Olena Borshch ◽  
Volodymyr Borshch ◽  
Dmytro Guzyk
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Boundary Conditions ◽  
Thermal Diffusion ◽  
Thermal State ◽  
Thermal Mode ◽  
Temperature Mode ◽  
Deep Layers

In barrier building constructions the heat transfer occurs both at the expense of thermal conductivity and as a result of liquid and air vapors resistance. The mechanism of such resistance differs from classical processes of diffusion and the laws of hydrodynamics for integral medium.The temperature mode of the surface and deep layers of barrier building constructions in non-symmetric boundary conditions was     analyzed. A mathematical model was developed that characterizes the change in the thermal state of barrier constructions during thermal diffusion. The method for calculating the non-stationary thermal modes of flat walls was presented.  

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 Analysis of Heat Transfer in the Structures with Regularly Arranged Gas Cavities

2008 ◽  
Vol 45 (4) ◽  
pp. 14-24 ◽  
Author(s):  
D. Cepīte ◽  
A. Jakovičs
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Conduction ◽  
Building Materials ◽  
Material Structure ◽  
Radiation Heat ◽  
Parallel Orientation ◽  
Transfer Processes ◽  
Radiation Heat Exchange

Analysis of Heat Transfer in the Structures with Regularly Arranged Gas CavitiesIn the work, the effective thermal conductivity (ETC) of anisotropic composite material (well-conducting media with regular cavities of the air) is studied by numerical modelling. The authors examine the influence of orientation and size of the cavities on the ETC of material structure and the role of thermal conduction, convection and radiation in the heat transfer processes. For modelling,Keratermtype material was chosen. It has been proved numerically that the ETC of similar structures is lower in the case when the cavities are oriented perpendicularly to the heat flux direction as compared with parallel orientation. According to the analysis performed, the radiation heat exchange in such cavities dominates over the convective heat transfer in the observed temperature range. In the calculations of ETC in structures of the kind, convection inside the cavities can be omitted. The proposed approach allows optimisation of the arrangement and size of the cavities in similar building materials.

scholarly journals THE ACTIVE METHOD OF CONTROL THE THERMAL CONDUCTIVITY OF BUILDING MATERIALS AND PRODUCTS

2019 ◽  
Vol 4 (7) ◽  
pp. 57-62
Author(s):  
Д. Карпов ◽  
Denis Karpov
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Test Object ◽  
Building Materials ◽  
Thermal Control ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Transfer Resistance ◽  
Non Destructive ◽  
Controlled Object

Thermal control refers to non-destructive testing methods. There are passive and active thermal non-destructive testing. With passive thermal control, the test object is characterized by a temperature field formed during its operation. With active thermal control, an additional source of thermal stimulation of the controlled object is used. Thermal control is widely used in various sectors of construction, energy, engineering and transport. The paper proposes a variant of active thermal non-destructive control of thermal conductivity coefficient of building materials and products on the example of a fragment of a building structure made of silicate bricks. The controlled object is subjected to thermal stimulation by an external source of thermal energy until the fixed thermal regime. Thermography of the test object surfaces is performed. The average values of surfaces temperature or individual sections of controlled object are calculated. The heat equation determines a controlled parameter - the heat coefficient of the object under control. The thermal resistance (heat transfer resistance) of the controlled object is calculated with a known coefficient of thermal conductivity. The heat transfer coefficient is calculated with a known coefficient of thermal resistance (heat transfer resistance). The method is implemented in the laboratory. It can be used in field and operating conditions for accurate and rapid determination of the key thermal properties of building materials and products.

Effects of Exterior Sun Shades on Heat Transfer by Solar Radiation

2014 ◽  
Vol 935 ◽  
pp. 61-65 ◽  
Author(s):  
Chih Hong Huang ◽  
Shin Yu Tsai
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Building Materials ◽  
Precast Concrete ◽  
Climatic Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wall Structures ◽  
Solar Radiation Intensity ◽  
Reduced Scale

Heat transfer in walls, as affected by climatic conditions such as fluctuations in outside air temperature, solar radiation intensity and wind speed as well as wall structures and heat transfer coefficients of materials, becomes a complex and non-steady state. The aim of this paper is to examine the relationship between total whole-day solar radiation and heat absorbed by and released from materials. An reduced scale of experiment was conducted using reduced scale precast concrete slabs and focusing on the effect of heat transfer involving solar radiation, building materials and shading rate. The results show that even though the sun shadings would stem partly the solar radiation into the wall, yet they obstruct in the mean time the release of the heat, which absorbed hours ago. That leads to a temperature raise and uncomfort to the interiors.

scholarly journals Features and results of assessment the thermal conductivity of building materials and products by the active method of thermal non-destructive testing

2020 ◽  
Vol 220 ◽  
pp. 01053
Author(s):  
Denis Karpov ◽  
Mikhail Pavlov ◽  
Liliya Mukhametova ◽  
Anton A. Mikhin
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Test Object ◽  
Building Materials ◽  
Thermal Control ◽  
External Source ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Operational Conditions ◽  
Non Destructive

Thermal control (passive and active) is a non-destructive testing method. During passive thermal control, the test object is characterized by a temperature field formed during its operation. In active thermal control, the test object is additionally thermally stimulated. This technique is widely used in various areas of construction, energy, mechanical engineering, transport. This paper proposes a variant of active thermal non-destructive assessment of the thermal conductivity coefficient of building materials and products on the example of a fragment of a building structure made of silicate bricks. The test object is subjected to thermal stimulation by an external source of thermal energy before reaching a steady-state thermal regime. Thermography of the test object surfaces is carried out. The average integral temperatures of surfaces or individual sections of the test object are calculated. The coefficient of thermal conductivity of the test object is determined, which is used to calculate its thermal resistance (resistance to heat transfer). After that, the coefficient of heat transfer is calculated. The method was implemented in laboratory conditions. It can be used in natural and operational conditions for accurate and quick determination of the key thermophysical properties of building materials and products.

scholarly journals Skeletal heat conductivity of porous metal fiber materials

2021 ◽  
Vol 27 (2) ◽  
pp. 70-77
Author(s):  
A.G. Kostornov ◽  
◽  
A.A. Shapoval ◽  
I.V. Shapoval ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Materials ◽  
Porous Metal ◽  
Heat Pipes ◽  
Metal Fiber ◽  
Two Phase ◽  
Research Results ◽  
Fiber Materials ◽  
Two Phase Heat Transfer

The influence of a number of physical characteristics and parameters of metallic fiber materials on their thermal conductivity is studied in this work. Such porous materials are intended, among other things, for their effective use in two-phase heat transfer devices (heat pipes). The use of heat pipes in aircraft and space vehicles provides a number of thermophysical advantages. In particular, heat pipes significantly expand the possibilities of air cooling of heat-loaded technical devices. The thermal conductivity of capillary-porous materials-structures, which are important elements of heat pipes, significantly affects the intensity of two-phase heat transfer inside heat pipes. Frame thermal conductivity is equivalent to the thermal conductivity of materials that are conditionally continuous medium. Studies of the influence of structural characteristics of porous materials, such as porosity and parameters (dimensions) of discrete particles-fibers (fractions of the studied materials), were performed using special experimental equipment created at the I.M. Frantsevich Institute for Problems of Materials Science of the National Academy of Sciences of Ukraine (Kyiv). Porous metal structures (coatings) made of copper, nickel, and steel fibers (MPM) were investigated under conditions similar to those for space heat pipes. The porosity values ​​of the prototypes of materials were in the range of 40 to 93%. The research results showed that the following physical characteristics of capillary structures, such as values ​​of thermal conductivity of metallic materials (fiber fractions), the porosity of capillary-porous metal materials (structures), significantly affect the value of thermal conductivity of porous materials. The dimensions of discrete particles-fibers also affect in a certain way the value of the MBM thermal conductivity but to a lesser degree. The results obtained in this work are summarized in the form of empirical dependencies – formulas, providing engineering calculations of the thermal conductivity values ​​of metal fiber materials. The research results are intended for practical application in aviation and spacecraft apparatus engineering. In particular, the presented results are necessary for the development and creation of effective heat pipes with metal fiber capillary structures.

Refinement of the thermal analysis of the gearbox taking into account the thermal conductivity of the joint

2021 ◽  
Author(s):  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Heat Transfer Coefficient ◽  
Thermal Conductivity Coefficient ◽  
Operating Temperature ◽  
Roughness Parameter ◽  
Tightening Force ◽  
Materials Used ◽  
Contact Thermal Conductivity

The existing method for calculating the operating temperature of the gearbox housing is clarified by taking into account the thermal conductivity coefficient of the contact, the value of which depends on the materials used for the housing and frame, the finish of the supporting surfaces and their area, as well as on the tightening force of the screws that pull the housing to the frame. An example of calculating the temperature of the housing of a worm gear is given. Keywords: gearbox, heat sink, heat transfer coefficient, thermal conductivity coefficient of contact, thermal conductivity coefficient of materials, roughness parameter. [email protected]

scholarly journals Moisture transfer in outer walls with layers of different density

2021 ◽  
Vol 327 ◽  
pp. 01005
Author(s):  
Andrey Rymarov ◽  
Dmitriy Titkov ◽  
Aleksey Ananiev
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Water Vapor ◽  
Building Materials ◽  
Moisture Transfer ◽  
Outer Wall ◽  
Vapor Permeability ◽  
Layer By Layer ◽  
Transfer Resistance ◽  
Concrete Blocks

The need to protect external walls from excess moisture to improve heat-shielding properties is an urgent task. If the outer wall is created from expanded clay concrete blocks, then the most interesting are the blocks created by layer-by-layer moulding, in which each layer can have its own given density. In such blocks, each layer has its own coefficients of thermal conductivity and vapor permeability, which allows you to select the required heat transfer resistance and vapor permeability of the outer wall for a specific region, taking into account the characteristics of the climate. The ability to have external walls with different material densities inside makes it possible to implement energy saving tasks in the building. The article discusses options for external walls made of expanded clay concrete blocks with layers with different densities and coefficients of thermal conductivity and vapor permeability. Changing the location of layers with different densities inside the blocks changes the local values of the vapor permeability resistance, which leads to a different nature of the movement of water vapor inside the wall in winter. It is good when water vapor does not accumulate in the wall; it does not condense and freely goes into the external environment. A dry wall is more durable, it loses less heat in winter. Changes in partial pressures at full saturation and with existing humidity inside the expanded clay concrete block for layers of different densities in winter are considered to determine the possible condensation from water vapor inside the wall. Layer-by-layer moulding of building materials improves their properties to increase resistance to heat transfer and to form a dry and more durable outer wall.

scholarly journals Mathematical modeling of heat transfer in a closed two- phase thermosyphon

2019 ◽  
Vol 21 (3) ◽  
pp. 3-13
Author(s):  
V. I. Maksimov ◽  
A. Е. Nurpeiis
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Heat Flow ◽  
Problem Solution ◽  
Two Phase ◽  
Evaporation Zone ◽  
Characteristic Temperatures ◽  
Simulation Results

We suggested a new approach for describing heat transfer in thermosyphons and determining the characteristic temperatures. The processes of thermogravitation convection in the coolant layer at the lower cap, phase transitions in the evaporation zone, heat transfer as a result of conduction in the lower cap are described at the problem statement. The main assumption, which was used during the problem formulation, is that the characteristic times of steam motion through the thermosyphon channel are much less than the characteristic times of thermal conductivity and free convection in the coolant layer at the lower cap of the thermosyphon. For this reason, the processes of steam motion in the thermosyphon channel, the condensate film on the upper cap and the vertical walls were not considered. The problem solution domain is a thermosyphon through which heat is removed from the energy-saturated equipment. The ranges of heat flow changes were chosen based on experimental data. The geometric parameters of thermosyphon and the fill factors were chosen the same as in the experiments (height is 161 mm, diameter is 42 mm, wall thickness is 1.5 mm, ε=4-16%) for subsequent comparison of numerical simulation results and experimental data. In the numerical analysis it was assumed that the thermophysical properties of thermosyphon and coolant caps do not depend on temperature; laminar flow regime was considered. The dimensionless equations of vortex, Poisson and energy transfer for the liquid coolant under natural convection and the equations of thermal conductivity for the lower cap wall are solved by the method of finite differences. Numerical simulation results showed the relationship between the characteristic temperatures and the heat flow supplied to the bottom cap of thermosyphon. The results of the theoretical analysis are in satisfactory agreement with the known experimental data. 

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