scholarly journals Determination of the thermal time constant of the reinforced concrete building component

2017 ◽  
Vol 66 (2) ◽  
pp. 79-90
Author(s):  
Stefan Owczarek ◽  
Mariusz Owczarek
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Transient State ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Building Component ◽  
Steady State Heat ◽  
The One ◽  
Standard Calculation ◽  
Building Physics

As a result of changes in the boundary conditions, a heat exchange in the building envelope is not always in a steady state. Heat fluxes penetrating through the wall may be several times greater than the steady state. Thus, the building can have a much higher demand for energy and requires the use of more powerful heater than it results from the standard calculation. This article dealt with estimating the length of the transient state after changing the boundary conditions. The protective celling plate of dimensions 35 m × 1 m and a thickness of 0.5 m has been analysed. The plate, on the one hand, is cooled in air at a temperature of 8.6°C, on the other hand is inside the shelter at 20°C. A period of cooling, based on the theoretical and numerical calculations, was obtained, then the differences were discussed and the conclusions drawn. Keywords: building, building physics, heat flows in building envelopes

scholarly journals Heat Transport Analysis in Rectangular Shields Using the Laplace and Poisson Equations

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1714
Author(s):  
Stefan Owczarek ◽  
Mariusz Owczarek
Keyword(s):  
Temperature Field ◽  
Steady State ◽  
Heat Flow ◽  
Direct Method ◽  
Transient State ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Flow Process ◽  
Infinite Power ◽  
Building Physics

In the design of a building envelope, there is the issue of heat flow through the partitions. In the heat flow process, we distinguish steady and dynamic states in which heat fluxes need to be obtained as part of building physics calculations. This article describes the issue of determining the size of those heat fluxes. The search for the temperature field in a two-dimensional problem is common in building physics and heat exchange in general. Both numerical and analytical methods can be used to obtain a solution. Two methods were dealt with, the first of which was used to obtain the solution in the steady state and the other in the transient. In the steady state a method of initial functions, the basics of which were given by W.Z. Vlasov and A.Y. Lur’e was adopted. Originally MIF was used for analysis of the loads of a flat elastic medium. Since then it was used for solving concrete beams, plates and composite materials problems. Polynomial half-reverse solutions are used in the theory of a continuous medium. Here solutions were obtained by the direct method. As a result, polynomial forms of the considered temperature field were obtained. A Cartesian coordinate system and rectangular shape of the plate were assumed. The problem is governed by the Laplace equation in the steady state and Poisson in the transient state. Boundary conditions in the form of temperature (τ(x), t(y)) or/and flux (p(x), q(y)) can be provided. In the steady state the solution T(x, y) was assumed in the form of an infinite power series developed in relation to the variable y with coefficients Cn depending on x. The assumed solution was substituted into the Fourier equation and after expanding into the Taylor series the boundary condition for y = 0 and y = h was taken into account. From this condition the coefficient Cn can be calculated and, therefore, a closed solution for the temperature field in the plate.

Determining Temperature Regulating Factor for Refrigeration Engineering Phase Change Material

2014 ◽  
Vol 521 ◽  
pp. 605-608
Author(s):  
Jia Zheng ◽  
Jie Li ◽  
Xiang Yi Guan ◽  
Shuang Han ◽  
Yi Ming Zhang
Keyword(s):  
Steady State ◽  
Phase Change ◽  
Phase Change Material ◽  
Transient State ◽  
Clothing Industry ◽  
Flux Variation ◽  
Test Instrument ◽  
Steady State Heat ◽  
Comfort Parameters ◽  
Change Material

In order to characterize the temperature regulating ability of fabrics containing phase change material (PCM), the test has been designed. To assess temperature regulating ability, temperature regulating factor (TRF) is determined. TRF is defined as a quotient of the amplitude of the temperature variation of the hot plate and the amplitude of the heat flux variation divided by the steady state heat resistance of the fabric. The test instrument presented here is intended to be used for testing steady state and transient state characteristics of the apparel fabrics containing the PCMs. This test instrument can be used in quality control during the manufacture of fabrics containing PCMs. TRF can be used in clothing industry to establish the criteria for comfort parameters of textiles.

scholarly journals Non-steady-state heat conduction in composite walls

2014 ◽  
Vol 470 (2165) ◽  
pp. 20130605 ◽  
Author(s):  
Bernard Deconinck ◽  
Beatrice Pelloni ◽  
Natalie E. Sheils
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Steady State ◽  
Composite Materials ◽  
Solution Method ◽  
One Dimensional ◽  
Infinite Domains ◽  
Steady State Heat ◽  
The One ◽  
Composite Walls

The problem of heat conduction in one-dimensional piecewise homogeneous composite materials is examined by providing an explicit solution of the one-dimensional heat equation in each domain. The location of the interfaces is known, but neither temperature nor heat flux is prescribed there. Instead, the physical assumptions of their continuity at the interfaces are the only conditions imposed. The problem of two semi-infinite domains and that of two finite-sized domains are examined in detail. We indicate also how to extend the solution method to the setting of one finite-sized domain surrounded on both sides by semi-infinite domains, and on that of three finite-sized domains.

scholarly journals A computational method to solve for the heat conduction temperature field based on data-driven approach

2021 ◽  
pp. 165-165
Author(s):  
Kun Li ◽  
Shiquan Shan ◽  
Qi Zhang ◽  
Xichuan Cai ◽  
Zhou Zhijun
Keyword(s):  
Temperature Field ◽  
Heat Conduction ◽  
Steady State ◽  
Transient State ◽  
Absolute Error ◽  
Computational Method ◽  
Data Driven ◽  
One Dimensional ◽  
Data Driven Approach ◽  
The One

In this paper, a computational method for solving for the one-dimensional heat conduction temperature field is proposed based on a data-driven approach. The traditional numerical solution requires algebraic processing of the heat conduction differential equations, and necessitates the use of a complex mathematical derivation process to solve for the temperature field. In this paper, a temperature field solution model called HTM (Hidden Temperature Method) is proposed. This model uses an artificial neural network to establish the correspondence relationship of the node temperature values during the iterative process, so as to obtain the "Data to Data" solution. In this work, one example of one-dimensional steady state and three examples of one-dimensional transient state are selected, and the calculated values are compared to those obtained by traditional numerical methods. The mean-absolute error(MAE)of the steady state is only 0.2508, and among the three transient cases, the maximum mean-square error(MSE) is only 2.6875, indicating that the model is highly accurate in both steady-state and transient conditions. This shows that the HTM simulation can be applied to the solution of the heat conduction temperature field. This study provides a basis for the further optimization of the HTM algorithm.

Collocation Trefftz Method for the Heat Conduction Issue in Irregular Domain

2012 ◽  
Vol 516-517 ◽  
pp. 146-155 ◽  
Author(s):  
Hong Ming Fan ◽  
Dan Zhang ◽  
Hang Yu
Keyword(s):  
Heat Conduction ◽  
Steady State ◽  
Boundary Conditions ◽  
Analytical Method ◽  
Arbitrary Shape ◽  
Form Solution ◽  
Irregular Domain ◽  
Trefftz Method ◽  
Steady State Heat ◽  
Separated Variables

Rules for non-orthogonal borders of irregular domain is the thorny issues when using analytical method for solving mathematical and physical equations. On the basis of solution in the form of separated variables, the border of arbitrary shape with non-orthogonal boundary will be separated into a limited number of discrete points, and then direct assignment for the form solution at each of the discrete points on the border according to boundary conditions, at every discrete points on the border can establish an equation. If the number of discrete points on the border is the same with truncated series after retained series, all coefficients of the form solution can be determined and the problem solved. This paper use Laplace equation as an example to illustrate Collocation Trefftz Method can solve certain steady-state heat conduction problems within non-orthogonal border and irregular domain.

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