scholarly journals Thermal resistance of the ventilated air-spaces behind external claddings; theoretical definition and a parametric study

2021 ◽  
Vol 2069 (1) ◽  
pp. 012197
Author(s):  
M Rahiminejad ◽  
D Khovalyg
Keyword(s):  
Thermal Resistance ◽  
Dynamic Parameter ◽  
Building Envelope ◽  
Numerical Code ◽  
Physical Parameters ◽  
Linear Network ◽  
Closed Cavity ◽  
Steady State Condition ◽  
Air Space ◽  
Definition Of

Abstract The presence of a ventilated air cavity between the external cladding and the wall core of a wall assembly can have a varying contribution to the thermal performance of the building envelope. In particular, the thermal resistance of a ventilated air-space is a dynamic parameter that is influenced by various thermo-physical parameters. In this study, a theoretical definition of the thermal resistance of a ventilated air-space behind an external cladding is introduced, employing a non-linear network of thermal resistances in the air-space. A numerical code is developed for the steady-state condition and verified with data from hot box tests available in the literature. Thereafter, a parametric analysis is performed based on the air change rate in the cavity (0 to 1000 1/h), type of the external cladding (brick and vinyl siding), seasonal variation (summer and winter conditions), and presence of the reflective insulation. The results are compared with a closed cavity to see the efficiency of the ventilation in the air-space. The results confirm that the theoretical thermal resistance of the ventilated air-space is a function of multiple factors, and its magnitude varies under different conditions.

scholarly journals Effects of the Circuit Arrangement on the Thermal Performance of Double U-Tube Ground Heat Exchangers

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3275
Author(s):  
Aminhossein Jahanbin ◽  
Giovanni Semprini ◽  
Andrea Natale Impiombato ◽  
Cesare Biserni ◽  
Eugenia Rossi di Schio
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Numerical Code ◽  
Geometrical Parameters ◽  
Fluid Temperature ◽  
The Finite Element Method ◽  
Ground Heat Exchangers ◽  
Borehole Thermal Resistance ◽  
The Impact ◽  
Circuit Configuration

Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.

scholarly journals Optimization of the level of thermal insulation of enclosing structures of civil buildings

2018 ◽  
Vol 245 ◽  
pp. 06002 ◽  
Author(s):  
Jurgis Zemitis ◽  
Maxim Terekh
Keyword(s):  
Thermal Resistance ◽  
Thermal Insulation ◽  
Economic Efficiency ◽  
Heat Insulation ◽  
Optimal Level ◽  
Economic Conditions ◽  
Additional Heat ◽  
Heat Protection ◽  
Definition Of ◽  
The Given

In the work, methods of an estimation of economic efficiency of additional heat insulation of building enclosing structures and definition of an optimum thermal resistance are considered, deficiencies of the given techniques are marked. A model is proposed for determining the optimal level of heat protection in the new economic conditions.

scholarly journals The Laboratory Definition of the Thermal Resistance of Growing Media for Green Roofs: New Experimental Setups

Buildings ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 139 ◽  
Author(s):  
Benedetta Barozzi ◽  
Alice Bellazzi ◽  
Claudio Maffè ◽  
Italo Meroni
Keyword(s):  
Thermal Resistance ◽  
Working Conditions ◽  
Laboratory Tests ◽  
National Research Council ◽  
Green Roofs ◽  
Growing Media ◽  
Experimental Campaign ◽  
Methodological Approaches ◽  
Set Up ◽  
Definition Of

Green roofs are one of the most extensively investigated roofing technologies. Most of the bibliographical studies show results of researches focused on the analysis of different configurations of green roofs, but only few researches deal with the calculation of the growing media thermal resistance using laboratory tests. From 2009 to 2013, ITC-CNR, the Construction Technologies Institute of the National Research Council of Italy, carried out a first laboratory experimental campaign focused on the definition of thermal performances curves of growing media for green roofs as a function of both density and percentage of internal moisture. During this campaign, the experimental results underlined some existing gaps, such as the absence of specific standards concerning the sample laboratory preparation, the absence of shared references concerning the compaction level reached by samples in real working conditions and the evaluation of the internal moisture content of growing media exposed to atmospheric agents. For this reason, the ITC-CNR has set up a second experimental campaign focused on the solution of the gaps underlined by the first phase concerning the preparation of samples for the laboratory calculation of the thermal resistance of growing media for green roofs. This paper proposes and presents methodological approaches, methods and new test devices implemented to solve these gaps, and the results obtained.

In Situ Measurement of Thermal Resistance of Building Envelope at the Residential Occupancy in Indonesia

2015 ◽  
Vol 771 ◽  
pp. 191-194 ◽  
Author(s):  
Wahyu Sujatmiko ◽  
Hermawan Kresno Dipojono ◽  
F.X. Nugroho Soelami ◽  
Soegijanto
Keyword(s):  
Thermal Resistance ◽  
High Performance ◽  
Building Materials ◽  
Precast Concrete ◽  
Green Building ◽  
Building Envelope ◽  
Building Wall ◽  
Ashrae Standards ◽  
Building Walls

Abstract. This paper presents the measurement results of three building wall materials which are commonly used for residential housings in Indonesia, namely clay brick, batako (concrete brick), and precast concrete. In-situ measurement of the steady state thermal flow (heat flux) at building walls (envelopes) is conducted in order to determine the thermal resistance of building wall according to ASTM C1155. The results show that all three building materials having a thermal resistance values are far below the energy conservation provisions of ASHRAE 90.1 and especially when compared to the provision of high performance green building ASHRAE 189.1 It is found that precast concrete has higher thermal resistance (or has lower thermal conductivity) than that of other two materials, hence a better compliance to the ASHRAE standards.

Discussions on the Convergence of the Seakeeping Simulations Based on the Panel Methods

2018 ◽  
Author(s):  
Ivana Martić ◽  
Nastia Degiuli ◽  
Šime Malenica ◽  
Andrea Farkas
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Surface Condition ◽  
Wave Length ◽  
Boundary Integral ◽  
The Body ◽  
Numerical Code ◽  
Physical Parameters ◽  
Diffraction Radiation ◽  
Panel Methods

Numerical problems related to the convergence of the classical panel methods which are employed for the diffraction-radiation simulations are discussed. It is well known that, for the panel methods, the convergence issues are not exclusively related to the physical parameters (wave length, body shape, draught ...) but also to the one purely numerical phenomenon which occurs when the Boundary Integral Equation Method (BIEM) based on the use of Kelvin (wave) type Green’s function is used. Indeed, due to the fact that the Green’s function satisfies the free surface condition in the whole fluid domain below z = 0, the numerical solution is polluted, at some particular frequencies, by the solution of the unphysical problem inside the body. This phenomenon which is purely numerical, is known as the problem of irregular frequencies. From practical point of view, it is not always easy to distinguish if the irregularities in the final solution are coming, from the body mesh which is not fine enough, from the physical resonance of the system, from the problem of irregular frequencies or from something else!? In this paper the authors discuss these issues in the context of the evaluation of the seakeeping behavior of one typical FPSO (Floating Production Storage and Offloading). Both the linear (first order) as well as the second order quantities are of concern and the different methods for the elimination of the irregular frequencies are discussed. Special attention is given to the calculations of the different physical quantities at very high frequencies. The numerical tool used within this research is the Bureau Veritas numerical code HYDROSTAR which is based on the panel method with singularities of constant strength.

STRONGLY CORRELATED FUNCTIONS IN RELIABILITY—PHYSICAL APPROACH

1994 ◽  
Vol 01 (01) ◽  
pp. 63-69 ◽  
Author(s):  
ANDREW H. RAWICZ
Keyword(s):  
Heat Conductivity ◽  
Electrical Resistance ◽  
Physical Parameters ◽  
Strongly Correlated ◽  
Acoustic Attenuation ◽  
Chemical Parameter ◽  
New Approach ◽  
Reliability Measure ◽  
Physical Chemical ◽  
Definition Of

A new approach to reliability called Strongly Correlated Functions is proposed in this paper based on the definition of reliability as a physical magnitude rather than as a probabilistic one. The reliability measure (e.g., life-length) of a component or a product treated as a physical/chemical parameter allows for the construction of analytic correlations between the reliability measure and other physical parameters such as electrical resistance, heat conductivity, or acoustic attenuation that can be nondestructively and quickly determined by a direct measurement. Examples of Strongly Correlated Functions applied to micro wire-joints are presented.

scholarly journals Extraction of the deterministic ingredient of a dynamic geodetic control network

2012 ◽  
Vol 2 (1) ◽  
pp. 68-75 ◽  
Author(s):  
L. Shahar ◽  
G. Even-Tzur
Keyword(s):  
Kinematic Model ◽  
Simultaneous Estimation ◽  
Physical Parameters ◽  
Control Network ◽  
Deformation Parameters ◽  
Free Network ◽  
Geodetic Control ◽  
Definition Of ◽  
Minimum Constraints ◽  
Entire Network

Extraction of the deterministic ingredient of a dynamic geodetic control networkA minimum constraints solution, which resolves the datum defect of a control network, is an arbitrary solution that may result in a systematic error in the estimation of the deformation parameters. This error is not derived from measurements and is usually inconsistent with the geophysical reality. A free network is affected only by errors of measurement and, therefore, a free network is an accepted way of coping with this problem. Study of deformations, which is based on the use of geodetic measurements, is usually performed today by defining a kinematic model. Such a model, when used to describe a complex geophysical environment, can lead to the partial estimation of the deterministic dynamics, which characterize the entire network. These dynamics are themselves expressed in measurements, as the adjustment systems' residuals. The current paper presents an extension of the definition of the parameters that are revalued. This extension enables the cleaning of measurements by means of the extraction of datum elements that have been defined by geodetic measurement. This cleaning minimizes the effects of these elements on the revaluated deformation. The proposed algorithm may be applied to achieve the simultaneous estimation of the physical parameters that define the geophysical activity in the network.

Wind Turbine Blade Structure Parameterization Using T4T

2014 ◽  
Author(s):  
Giorgos A. Strofylas ◽  
Georgios I. Mazanakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Wind Turbine ◽  
Parametric Design ◽  
Turbine Blades ◽  
Design Procedure ◽  
Software Tool ◽  
Computational Procedure ◽  
Physical Parameters ◽  
Wind Turbine Blades ◽  
Definition Of ◽  
Cloud Of Points

A software tool named “T4T” (Tools for Turbomachinery) has been developed for the parametric design of turbomachinery and wind turbine blades. The complete design procedure is object-oriented and parametric, providing the ability to the user to define various types of blades. It has been developed in QT C++, utilizing OpenCascade graphical and computational libraries. The software allows the user to design the outer surface either by specifying some physical parameters for each blade section, or by directly interpolating a surface through a cloud of points. The new/enhanced version of “T4T” software tool, introducing the definition of internal blade structure for wind turbines rotors, is fully parametric and customizable, allowing the user for defining the internal blade structure, including shear webs. The computational procedure finally produces compound solids, which can be further imported to mesh generation and analysis software through standard geometry exchange protocols, for cooperation with CFD and CSD solvers.

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