MATHEMATICAL MODELING OF THERMAL EFFICIENCY OF BUILDING EN-VELOPE OF MULTI-STOREY BUILDINGS WITH ACCOUNT OF INDIVIDUAL INSULATION

2021 ◽  
pp. 46-58
Author(s):  
A. Ganzha ◽  
L. Semenenko ◽  
Yu. Bronevskyi ◽  
Yu. Savraieva
Keyword(s):  
Mathematical Modeling ◽  
Heat Flux ◽  
Thermal Insulation ◽  
Three Dimensional ◽  
Total Heat ◽  
Actual Condition ◽  
Heating Systems ◽  
One Dimensional ◽  
Thermal Bridges

At present, the problem of general thermal modernization of building envelopes is given much attention both at the level of scientists and consumers. This is one of the effective ways to reduce natural gas consumption, reduce the negative impact on the environment, maintain and improve comfortable indoor conditions. Over the last decade, the population has rapidly begun to insulate their homes in order to raise the indoor air temperature to a comfortable level in the multi-storey residential sector. Due to insufficient attention of the authorities in the housing and communal sector, the lack of scientific research and widespread public awareness, there is a massive thermal insulation of building by residents of multi-store buildings within their own apartments. But the study of thermal processes that occur in individual thermal insulation of enclosing structures is currently not fully completed. Therefore, in the context of significant increases in gas and electricity prices, this problem is relevant. In the study was carried out mathematical modeling of a fragment of a partially insulated wall of an enclosing structure with determination of heat flux by solving a three-dimensional differential equation of thermal conductivity with boundary conditions of II, III and IV kind and distribution of characteristics of building structures and insulation. These results can be used in the analysis of the efficiency of insulation of the building taking into account the fragmentary insulation and of comparison with systemic thermal modernization. As a result of modeling, the three-dimensional temperature fields of wall surfaces, are determined, there are additional heat fluxes (thermal bridges), which are not considered in the simplified one-dimensional calculation. In one-dimensional calculation, the heat flux from the wall is reduced by 2.43 times during insulation. Taking into account the total heat flow from the side surfaces near the window (thermal bridges) and system insulation - by 1.75 times. With fragmentary insulation and considering the total heat flux from the side surfaces near the window - by 1.6 times. The next stage of calculations is the determination of the actual air temperatures in the premises of a multi-storey building considering the actual condition of enclosing structures and heating systems, heaters, mode parameters of the coolant and outdoor air parameters. The methods and means of this analysis can take into account the final data of heat loss adjustment after the mathematical modeling presented in this paper. In consequence, the results will be taken into account in the projects of thermal modernization of buildings, reconstruction of heating systems, rational placement of sources, selection of equipment and regulation of devices.

Measurement and Simulation of Water Hammer in Piping Systems Including Junction Coupling

2013 ◽  
Author(s):  
Stefan Riedelmeier ◽  
Stefan Becker ◽  
Eberhard Schlücker
Keyword(s):  
Three Dimensional ◽  
Water Hammer ◽  
Test Facility ◽  
One Dimensional ◽  
Beam Elements ◽  
Coupled Codes ◽  
Piping Systems ◽  
Complex Test ◽  
System Configurations

For the analysis of the effects of fluid-structure interaction (FSI) during water hammer in piping systems, a complex test facility was constructed. Resonance experiments with movable bends in two system configurations were carried out. The pressure and the displacement of the bend were recorded. The aim was to reproduce the results with two coupled codes: a one-dimensional solver based on the method of characteristics (MOC) for the hydraulic system and a three-dimensional solver based on the finite element method (FEM) working with one-dimensional beam elements for the structural system. The calculation included junction and friction coupling. The models were fine-tuned separately. For this purpose, special measurements were carried out. These included the determination of the structural damping, the friction factor, the influence of the bending of the anchorage, etc. After the validation of the models, the results of the coupled calculations were compared against the measurements, the performance of the coupled codes was evaluated and the most important physical effects were analyzed and are discussed.

scholarly journals The Influence of Different Facings of Polyisocyanurate Boards on Heat Transfer through the Wall Corners of Insulated Buildings

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1991 ◽  
Author(s):  
Tomas Makaveckas ◽  
Raimondas Bliūdžius ◽  
Arūnas Burlingis
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Insulation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Thermal Bridge ◽  
Thermal Bridges ◽  
The Impact ◽  
Heat Flow Meter

Polyisocyanurate (PIR) thermal insulation boards faced with carboard, plastic, aluminum, or multilayer facings are used for thermal insulation of buildings. Facing materials are selected according to the conditions of use of PIR products. 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 linear thermal bridge formed in the connection of PIR boards with facing of both walls. Analyzing the installation of PIR thermal insulation products on the walls of a building, the structural schemes of linear thermal bridges were created, numerical calculations of the heat transfer coefficients of the linear thermal bridges were performed, and the influence of various facings on the heat transfer through the thermal bridge was evaluated. Furthermore, an experimental measurement using a heat flow meter apparatus was performed in order to confirm the results obtained by numerical calculation. This study provides more understanding concerning the necessity to evaluate the impact of different thermal conductivity facings on the heat transfer through corners of buildings insulated with PIR boards.

The Volume of Motion: Introduction, Derivation, and an Application Comparing Various Spinal Fixation Devices

1993 ◽  
Vol 115 (1) ◽  
pp. 43-46 ◽  
Author(s):  
J. J. Crisco
Keyword(s):  
Rigid Body ◽  
Three Dimensional ◽  
Spinal Fixation ◽  
Dimensional Parameter ◽  
Directional Information ◽  
One Dimensional ◽  
Fixation Devices ◽  
Spinal Fixation Devices ◽  
Mathematical Derivation

Range of motion (ROM), the displacement between two limits, is one of the most common parameters used to describe joint kinematics. The ROM is a one-dimensional parameter, although the motion at many normal and pathological joints is three-dimensional. Certainly, the ROM yields vital information, but an overall measure of the three-dimensional mobility at a joint may also be useful. The volume of motion (VOM) is such a measure. The translational VOM is the volume defined by all possible ROMs of a point on a rigid body. The rotational VOM, although its interpretation is not as tangible as the translational VOM, is a measure of the three-dimensional rotational mobility of a rigid body. The magnitude of the VOM is proportional to mobility; the VOM is a scaler, which does not contain any directional information. Experimental determination of the VOM is not practical since it would require applying loads in an infinite number of directions. The mathematical derivation given here allows the VOM to be calculated, with the assumption of conservative elasticity, from the resultant displacements of three distinct load vectors of equal magnitude. An example of the VOM is presented in the comparison of the biomechanical stabilizing potential of various spinal fixation devices.

scholarly journals Effect of Vertical Pressure on Horizontal and Vertical Permeability of Soil and Effect of Surcharge Pressure on 3D Consolidation of Soil

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Arpan Laskar ◽  
Sujit Kumar Pal
Keyword(s):  
Soil Properties ◽  
Three Dimensional ◽  
Vertical Pressure ◽  
Soil Layers ◽  
One Dimensional ◽  
Consolidation Theory ◽  
Vertical Permeability ◽  
Homogeneous Soil ◽  
Soil Changes

Permeability and consolidation of soil are known as the most variable soil properties. The values of permeability and consolidation of soil may vary with depth even in case of homogeneous soil layers, and because of that, the determination of appropriate values of permeability and consolidation is a complex and complicated engineering task. In this study, horizontal and vertical permeability apparatus and a 3D (three-dimensional) consolidation apparatus are developed to determine the effects of vertical pressure on horizontal and vertical permeability and the effects of vertical surcharge pressures on three-dimensional consolidation of soil. A series of horizontal and vertical permeability tests of soil under different vertical pressures and a series of 3D consolidation tests under different surcharge pressures are performed. From the study, it is observed that the horizontal and vertical permeability of soil changes with the changes in vertical pressures, and 3D consolidation of soil also changes with the changes in surcharge pressures. The horizontal and vertical permeability values obtained from the newly developed horizontal and vertical permeability apparatus are used in Terzaghi’s one-dimensional consolidation theory to find out the consolidation characteristics of the soil, and it is compared with the results obtained from the newly developed 3D consolidation apparatus.

On the Spectra of Turbulent Velocity Field in a Stably Stratified Flow

1991 ◽  
Vol 46 (5) ◽  
pp. 462-468
Author(s):  
A. K. Chakraborty ◽  
B. E. Vembe ◽  
H. P. Mazumdar
Keyword(s):  
Heat Flux ◽  
Energy Spectrum ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Eddy Viscosity ◽  
Three Dimensional ◽  
Inertial Subrange ◽  
Coefficient Function ◽  
One Dimensional ◽  
Kinetic Energy Spectrum

Abstract This paper describes a method to solve the spectral equation for the balance of turbulent kinetic energy in a stably stratified turbulent shear flow. The cospectra of vertical momentum and heat flux arc modelled with the aid of a basic eddy-viscosity (or turbulent exchange coefficient) function. For the term representing the inertial transfer of turbulent kinetic energy, Pao's [Phys. Fluids 8 (1965)] form is assumed. Analytical expressions for the three-dimensional kinetic energy spectrum as well as the cospectra of momentum and heat flux are obtained over the range of wave numbers k≥kb, which includes the inertial subrange kb≪k≪ks and the viscous subrange k>ks (kb and ks are the buoyancy and Kolmogorov wavenumbers, respectively). The two one-dimensional spectra, e.g., the kinetic energy spectra of the horizontal and vertical components of turbulence are derived from the three-dimensional kinetic energy spectrum. These one-dimensional spectra are compared with the measured data of Gargett et al. [J. Fluid Mech. 144 (1984)] for the case I ( = ks/kb) = 630. Finally, we compute the basic eddy-viscosity function and discuss its behavio

A variational–Green's function approach to theoretical treatment and applications of the capacitance of three-dimensional geometries

1982 ◽  
Vol 60 (2) ◽  
pp. 179-195 ◽  
Author(s):  
Andreas Mandelis
Keyword(s):  
Thin Film ◽  
Spatial Distribution ◽  
Green’S Function ◽  
Green's Function ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Function Approach ◽  
Theoretical Treatment ◽  
One Dimensional

A combined variational–Green's function approach to the determination of the capacitance of various useful three-dimensional geometries is developed. This formalism leads to general, exact expressions for the capacitance, which can be used with all geometries provided the spatial distribution of the charge can be determined. In particular, the theory takes into account the finite thickness and unequal areas of the capacitor plates. Specific applications of the theory include circular capacitors with disc and ring-shaped charged plate geometries. Such geometries are commonly encountered in experimental set-ups for capacitive measurements of thin film thicknesses in the field of microelectronics. Numerical results indicate that the values of thin film thicknesses calculated via simplified one-dimensional formulae for the capacitance may be incorrect by more than 10%

scholarly journals Studies on Heat Flux Imparted on Thermal Insulation Inside Rocket Motor Containing Double Base Propellant

2019 ◽  
Author(s):  
Rakesh Kumar Kalal ◽  
Balesh Ropia ◽  
Himanshu Shekhar ◽  
Prashant Sudhir Alegaonkar
Keyword(s):  
Heat Flux ◽  
Experimental Determination ◽  
Thermal Insulation ◽  
Rocket Motor ◽  
Heat Flux Sensor ◽  
Thermal Insulator ◽  
Double Base ◽  
Measured Pressure ◽  
Flux Sensor

Thermal insulation inside the rocket motor experience severe pressure and temperature conditions. Experimental determination of heat flux imparted to thermal insulator inside the rocket motor during the static firing is a challenging task. This paper reports experimental determination of heat flux for double base propellant (DBP) in small rocket motor. It includes development of experimental rocket motor, adaptation of water-cooled heat flux sensor on rocket motor, required instrumentation for heat flux time recording and analysis of data. Data are recorded in real time for double base propellant combustion up to the pressure level ~3.6 MPa. Average heat flux imparted to the rocket motor casing is found in the range of 230–300 × 104 W/m2. Heat flux inside the rocket motor varies nearly linear with pressure. A correlation between the heat flux and pressure is also established for measured pressure range.

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