scholarly journals A new method to estimate point thermal transmittance based on combined two-dimensional heat flow calculation

2020 ◽  
Vol 172 ◽  
pp. 08005
Author(s):  
Jaanus Hallik ◽  
Targo Kalamees
Keyword(s):  
Heat Flow ◽  
Three Dimensional ◽  
Multiple Linear Regression Model ◽  
Building Envelope ◽  
New Method ◽  
Two Dimensional ◽  
Thermal Transmittance ◽  
Thermal Bridge ◽  
Thermal Bridges ◽  
Third Dimension

A well-insulated, airtight and thermal bridge free building envelope is a key factor for nearly zero energy buildings (nZEB). However, increased insulation thickness and minimized air leakages increase the effect of thermal bridges on overall energy efficiency of the nZEBs. Although several more prominent linear thermal bridges are accounted for in the practice the three-dimensional heat flow through vast array of fixation elements, mounting brackets and other point thermal bridges are usually neglected due to time-consuming model preparation routine, lack of input data as well as high number of different thermal bridges that have to be assessed for a single project. In this study a new method was proposed for predicting three-dimensional heat flow and the point thermal transmittance of thermal bridges caused by full or partial penetration of the building envelope with metal elements with uniform geometry in third dimension based on multiple two-dimensional numerical heat flow calculations. A new parameter (equivalent length of thermal bridge) was defined which incorporates the effect of additional thermal transmittance in third dimension when multiplied by the difference of two thermal coupling coefficients derived for two-dimensional cross section. Multiple linear regression model was fitted on database with 102 cases and verified with separate case of window to wall connection incorporating metal penetration at fixation points. The proposed methodology can be useful in general practice where the design team lacks the skills or software tools for conducting detailed numerical analysis in three dimensions.

scholarly journals Steady-State Three - Dimensional Numerical Simulation of Heat Transfer for Thermal Bridges Assessment

2016 ◽  
Vol 6 (1) ◽  
pp. 17-22
Author(s):  
Silviana Brata ◽  
Carmen Maduta ◽  
S. Pescari
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Flow ◽  
Three Dimensional ◽  
Outer Wall ◽  
Thermal Transmittance ◽  
State Heat ◽  
Thermal Bridges ◽  
Steady State Heat ◽  
Steady State Heat Transfer

Abstract This paper presents a study on using the steady-state three-dimensional heat transfer software HEAT3 for evaluating the heat flow of heat transfer through different elements of the building envelope in order to establish the linear thermal transmittance of the linear thermal bridge. The linear thermal transmittance is obtained according to the one-dimensional steady-state heat transfer calculation formula for the plane walls using the heat flow values obtained through the method specified above. The results presented in this paper are part of a wider study on evaluating the heat transfer through building’s envelope elements by evaluating as accurate as possible the thermal bridges effect of the most common building structures. As a case study, it was considered the steady-state heat transfer through an opaque outer wall of a building considering the thermal bridges for the following elements: outer walls intersection, inner and outer wall intersection and outer wall with intermediate floor intersection.

New Calculation Method for Determination of the Influence of Thermal Bridges on a Building

2016 ◽  
Vol 820 ◽  
pp. 183-188
Author(s):  
Rastislav Menďan ◽  
Monika Pavčeková
Keyword(s):  
Calculation Method ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Thermal Transmittance ◽  
Exact Determination ◽  
Thermal Bridges ◽  
Building Practice

The contribution presents a new calculation method for more exact determination of increase of thermal transmittance due to thermal bridges ΔU. Since each building is three-dimensional, to get the objective and exact results, the calculation of heat losses of a building should be carried out using three-dimensional model. However, the 3D calculation is practically rather difficult and very hard realizable in building practice in Slovakia nowadays. It is much simpler to model and calculate a building as two-dimensional. The calculation method presented in this contribution is based on the modeling two-dimensional sections of the whole building taking into account the building as a whole.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

scholarly journals Thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels: an experimental and computational study

2020 ◽  
Vol 172 ◽  
pp. 08001
Author(s):  
Paul Klõšeiko ◽  
Reimo Piir ◽  
Marti Jeltsov ◽  
Targo Kalamees
Keyword(s):  
Computational Study ◽  
Precast Concrete ◽  
Sandwich Panels ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Air Cavity ◽  
Thermal Transmittance ◽  
Thermal Bridge ◽  
Thermal Bridging ◽  
Air Cavities

The purpose of this work was to quantify the thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels (PCSPs). Special interest was in cases where the use of rigid insulation (e.g. PIR) would leave air gaps between insulation boards and diagonal ties, thus intensifying the thermal bridge. A climate chamber experiment using 5 different joint types was performed to gather reference data for CFD model validation. In the experiment, natural convection was observed in joints where no additional insulation was used, i.e. in air cavities. Significantly larger heat fluxes were measured in these cavities compared to insulated joints. The thermal bridging effect was evaluated for a typical PCSP (thermal transmittance without thermal bridges U = 0.11 W/(m²·K)) using CFD software taking into account 3D heat conduction and convection. Simulation results indicate that diagonal ties without adjacent air cavities increased the average thermal transmittance (U-value) of the envelope by 8%, diagonal ties with a 6 mm air cavity – 19...33% and diagonal ties with a 10 mm air cavity – 45...56%. In conclusion, it was found that the joints in insulation caused by diagonal ties affect the overall thermal performance of the building envelope significantly when efforts are not made to fill the air cavities around the connectors.

scholarly journals Three-Dimensional Coordination Number from Two-Dimensional Measurements: A New Method

1986 ◽  
Vol 32 (112) ◽  
pp. 391-396 ◽  
Author(s):  
Richard B. Alley
Keyword(s):  
Coordination Number ◽  
Three Dimensional ◽  
New Method ◽  
Two Dimensional ◽  
Shape Factors ◽  
Important Measure ◽  
Dimensional Measurements ◽  
Average Bond

AbstractThe average three-dimensional coordination number, n3, is an important measure of firn structure. The value of n3 can be estimated from n2, the average measured two-dimensional coordination number, and from a function, Γ, that depends only on the ratio of average bond radius to grain radius in the sample. This method is easy to apply and does not require the use of unknown shape factors or tunable parameters.

scholarly journals A Possible Three-Dimensional Mechanism for Oscillating Wobbles in Tropical Cyclone–Like Vortices with Concentric Eyewalls

2018 ◽  
Vol 75 (7) ◽  
pp. 2157-2174 ◽  
Author(s):  
Konstantinos Menelaou ◽  
M. K. Yau ◽  
Tsz-Kin Lai
Keyword(s):  
Tropical Cyclone ◽  
Nonlinear Model ◽  
Three Dimensional ◽  
The Other ◽  
Sensitivity Analyses ◽  
Two Dimensional ◽  
Triggering Mechanism ◽  
Eigenmode Analysis ◽  
Concentric Eyewalls ◽  
Third Dimension

Abstract It is known that concentric eyewalls can influence tropical cyclone (TC) intensity. However, they can also influence TC track. Observations indicate that TCs with concentric eyewalls are often accompanied by wobbling of the inner eyewall, a motion that gives rise to cycloidal tracks. Currently, there is no general consensus of what might constitute the dominant triggering mechanism of these wobbles. In this paper we revisit the fundamentals. The control case constitutes a TC with symmetric concentric eyewalls embedded in a quiescent environment. Two sets of experiments are conducted: one using a two-dimensional nondivergent nonlinear model and the other using a three-dimensional nonlinear model. It is found that when the system is two-dimensional, no wobbling of the inner eyewall is triggered. On the other hand, when the third dimension is introduced, an amplifying wobble is evident. This result contradicts the previous suggestion that wobbles occur only in asymmetric concentric eyewalls. It also contradicts the suggestion that environmental wind shear can be the main trigger. Examination of the dynamics along with complementary linear eigenmode analysis revealed the triggering mechanism to be the excitation of a three-dimensional exponentially growing azimuthal wavenumber-1 instability. This instability is induced by the coupling of two baroclinic vortex Rossby waves across the moat region. Additional sensitivity analyses involving reasonable modifications to vortex shape parameters, perturbation vertical length scale, and Rossby number reveal that this instability can be systematically the most excited. The growth rates are shown to peak for perturbations characterized by realistic vertical length scales, suggesting that this mechanism can be potentially relevant to actual TCs.

scholarly journals CASE-STUDY ANALYSIS OF CONCRETE LARGE-PANEL APARTMENT BUILDING AT PRE- AND POST LOW-BUDGET ENERGY-RENOVATION

2016 ◽  
Vol 23 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Kalle KUUSK ◽  
Targo KALAMEES ◽  
Siim LINK ◽  
Simo ILOMETS ◽  
Alo MIKOLA
Keyword(s):  
Co2 Concentration ◽  
Building Envelope ◽  
Study Analysis ◽  
Indoor Climate ◽  
Apartment Building ◽  
Case Study Analysis ◽  
Thermal Transmittance ◽  
Large Panel ◽  
Thermal Bridges

The paper presents a case study analysis of low-budget renovation of a typical concrete large-panel apartment building. Focus is on the measurements and analyses of energy consumption, indoor climate, CO2 concentration, air leakage rate, thermal transmittance of thermal bridges, and thermal transmittance of the building envelope before and after the renovation. Results indicate that the renovation project was generally successful, with delivered energy need de­creasing by 40% and heating energy need decreasing by 50%. However, some key problems need to be solved to achieve full energy efficiency potential of the renovation works. Those critical problems are the performance (thermal comfort, heat recovery) of ventilation systems, thermal bridges of external wall/window jamb and economic viability. Currently, a major renovation is not economically viable, therefore financial assistance to the apartment owners’ associations is required to encourage them to undertake major renovations.

scholarly journals 3D Dynamic Simulation of Heat Conduction through a Building Corner Using a BEM Model in the Frequency Domain

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4595
Author(s):  
Nuno Simões ◽  
Joana Prata ◽  
António Tadeu
Keyword(s):  
Frequency Domain ◽  
Three Dimensional ◽  
Dynamic Effect ◽  
Building Envelope ◽  
Heat Fluxes ◽  
Heat Flux Distribution ◽  
Thermal Bridge ◽  
Proposed Model ◽  
Moisture Condensation ◽  
Thermal Bridging

This paper sets out a three-dimensional (3D) boundary element method (BEM) formulation in the frequency domain to simulate heat transfer through a point thermal bridge (PTB) at a corner in a building envelope. The main purpose was to quantify the dynamic effect of a geometrical PTB in terms of distribution of temperatures and heat fluxes, which is useful for evaluating moisture condensation risk. The numerical model is first validated experimentally using a hot box to measure the dynamic heat behavior of a 3D timber building corner. The proposed model is then used to study the dynamic thermal bridging effect in the vicinity of a 3D concrete corner. Given the importance of the risk of condensation, this study looks at the influence of an insulating material and its position on the temperature and heat flux distribution through the PTB under steady state and dynamic conditions.

scholarly journals New insights into the suitability of the third dimension for visualizing multivariate/multidimensional data: A study based on loss of quality quantification

2014 ◽  
Vol 15 (1) ◽  
pp. 3-30 ◽  
Author(s):  
Antonio Gracia ◽  
Santiago González ◽  
Víctor Robles ◽  
Ernestina Menasalvas ◽  
Tatiana von Landesberger
Keyword(s):  
Analytical Approach ◽  
Distance Perception ◽  
Statistical Tests ◽  
Three Dimensional ◽  
Multidimensional Data ◽  
Two Dimensional ◽  
Dimensional Representation ◽  
The Third ◽  
Quality Degradation ◽  
Third Dimension

Most visualization techniques have traditionally used two-dimensional, instead of three-dimensional representations to visualize multidimensional and multivariate data. In this article, a way to demonstrate the underlying superiority of three-dimensional, with respect to two-dimensional, representation is proposed. Specifically, it is based on the inevitable quality degradation produced when reducing the data dimensionality. The problem is tackled from two different approaches: a visual and an analytical approach. First, a set of statistical tests (point classification, distance perception, and outlier identification) using the two-dimensional and three-dimensional visualization are carried out on a group of 40 users. The results indicate that there is an improvement in the accuracy introduced by the inclusion of a third dimension; however, these results do not allow to obtain definitive conclusions on the superiority of three-dimensional representation. Therefore, in order to draw further conclusions, a deeper study based on an analytical approach is proposed. The aim is to quantify the real loss of quality produced when the data are visualized in two-dimensional and three-dimensional spaces, in relation to the original data dimensionality, to analyze the difference between them. To achieve this, a recently proposed methodology is used. The results obtained by the analytical approach reported that the loss of quality reaches significantly high values only when switching from three-dimensional to two-dimensional representation. The considerable quality degradation suffered in the two-dimensional visualization strongly suggests the suitability of the third dimension to visualize data.

Beamtrees: Compact Visualization of Large Hierarchies

2003 ◽  
Vol 2 (1) ◽  
pp. 31-39 ◽  
Author(s):  
Frank van Ham ◽  
Jarke J. van Wijk
Keyword(s):  
Hierarchical Structure ◽  
User Study ◽  
Three Dimensional ◽  
New Method ◽  
Data Sets ◽  
Two Dimensional ◽  
Hierarchical Data ◽  
Organization Structures ◽  
The Hierarchical Structure

Beamtrees are a new method for the visualization of large hierarchical data sets, such as directory structures and organization structures. Nodes are shown as stacked circular beams such that both the hierarchical structure as well as the size of nodes are depicted. The dimensions of beams are calculated using a variation of the treemap algorithm. Both a two-dimensional and a three-dimensional variant are presented. A small user study indicated that beamtrees are significantly more effective than nested treemaps and cushion treemaps for the extraction of global hierarchical information.

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