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One dimensional model of transient heat conduction through multilayer walls/slabs: The functionality of insulation and brick materials in terms of decrement factor and time lag
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Energy Efficiency)ORCID iD: 0000-0002-2822-0000
(Energy Efficiency)
2016 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Abstract Multilayer wall is a common type of building envelope used in buildings located in cold climates. The building envelope is typically composed by internal and external masses made by bricks or concrete separated by a large thickness of insulation material. This paper investigates the thermal behavior of a multilayer wall subjected to temperature excitation on both wall sides. The analysis is conducted by discretizing the continuous space and time variables of the mathematical model identified in the heat equation. Euler backwards solves the numerical model of multilayer wall by providing an unconditionally stable solution. The step response test shows the correct working of the model which reaches the steady state solution. The results of this paper are expressed in terms of temperature of each wall layer against the time. In particular, (i) the large thickness of insulation material separates thermodynamically the outside external mass from the internal mass, (ii) 20 cm thickness of insulation material damps the heat wave with a decrement factor of 3.41 °ͦC and a time lag of 1 hour, (iii) the external brick layer damps the heat wave with a decrement factor of 1.97 °ͦC and a time lag of 5 hours.

Place, publisher, year, edition, pages
2016.
Keyword [en]
Heat equation, Euler Implicit solver, Multilayer walls/slabs, Finite Dierence Method
National Category
Civil Engineering
Research subject
Systems Analysis; Technical Physics
Identifiers
URN: urn:nbn:se:umu:diva-121200OAI: oai:DiVA.org:umu-121200DiVA: diva2:931581
Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-06-03
In thesis
1. Modelling and simulation of building components: thermal interaction between multilayer wall and hydronic radiator
Open this publication in new window or tab >>Modelling and simulation of building components: thermal interaction between multilayer wall and hydronic radiator
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Background and Scope The scope of this thesis is to investigate the thermal behaviour of building components as hydronic radiator and multilayer walls subjected to dynamic conditions. The modelling and simulation of these building components provide information on how these components thermally interact among each other. The thermal interaction is fundamental to know how the energy is used in buildings. In particular, the thermal energy used in rooms can be expressed as the efficiencies for emission in a space heating system. This thesis analyzes the efficiencies for emission of a space heating system equipped with hydronic radiator for Swedish buildings by providing a comprehensive and detailed approach on this topic.

 

Methodology The methods used in this thesis are: experiment, modelling of multilayer wall and hydronic radiator, the dynamic simulation of the building and the efficiencies for emission of a space heating system. Here, the experiment, known as step response test, shows the heating up process of a hydronic radiator. The observation of the qualitative measurements suggests the most suitable technique of modelling the radiator known as transient modelling with multiple storage elements. The multilayer wall has been discretized both in space and time variable with a Finite Difference Method. Dynamic simulation of the building provides the efficiencies for emission of a space heating system.

 

Findings The experimental results show how the radiator performs the charging phase. The performance of the transient model is compared with lumped steady state models in terms of temperature of exhaust flow and total heat emitted. Results of the dynamic simulation show how buildings located in a Northern climate use the energy in a better way than Southern climates in Sweden. Heavy active thermal mass provides higher efficiencies for emission than light thermal mass. Radiators with connection pipes located on the same side react faster at the thermodynamic changing of the mass flow rate by providing higher efficiencies for emission than radiators with connection pipes located on the opposite side.

 

Conclusion and Outlook This thesis increases the knowledge about the modelling and simulation of hydronic radiators and multilayer walls. More research is needed on this topic to encompass modelling details of building components often ignored. The modelling and simulation of building components are the key to understand how building components thermally interact with each other. The thermal interaction among building components is a fundamental parameter for the assessment of efficiencies of emission of the space heating system. In the near future, the concept of efficiencies of emission can be implemented in National Building Code, therefore, this study provides guidelines on how to assess these efficiencies.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 39 p.
Keyword
Hydronic radiator, multilayer wall, efficiencies of emission
National Category
Building Technologies
Research subject
Systems Analysis; Technical Physics
Identifiers
urn:nbn:se:umu:diva-121201 (URN)978-91-7601-515-5 (ISBN)
Presentation
2016-06-15, MC413, MIT-huset, Umeå University, Umeå, 13:00 (English)
Opponent
Supervisors
Note

Advisors: Ronny Östin and Mohsen Soleimanni Mohseni, Department of Applied Physics and Electronics, Umeå University

Available from: 2016-05-30 Created: 2016-05-30 Last updated: 2016-06-03Bibliographically approved

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