# Thermal coupling of leakage air and heat flows in buildings and in building components: Development and application of numerical methods: Dissertation

Markku Virtanen

Research output: ThesisDissertationMonograph

## Abstract

Numerical methods have been introduced for the thermal analysis of airleakages in building components and in buildings as a whole. Numericalmethods at the structure level are developed on the basis of physical modelling derived from the balance equations of coupled heat and airtransfer in building structures. The study focuses on crack and filtrationflows. The numerical formulation of the model equations is based on the finite difference method and the reliability of the two-dimensionalnumerical methods developed at the structural level have beenexperimentally confirmed. For energy analyses of buildings, an application of the response factor method for leaky structures, which takes intoaccount the thermal coupling of transmission heat flows and the convectionheat flows of air leakages, is also introduced. A simulation procedure for the simultaneous solution of air flow and heat balances is elaborated. Inthis procedure the heat balance of a building is solvedby means of the so-called convective heat balance model as well as the response factor method developed. The air flow balance is solved in a quasi steady-statecondition, using the MOVECOMP program as a basis. In the analyses at the structure level, the thermal interactions of structures and leakage air flows in some typical air leakage cases are examined. The dependence of heat transfer (the heat recovery effect) on the leakage air flow rate, the length and location of the leakage path, the dimensions and thermal property values of the structure and on the heat transfer coefficients of the surfaces are analysed numerically. The numerical analyses made on the building level are used to study the annual interactions between the airtightness of the building envelope, air leakages and heating energy consumption. A single family house with a mechanical exhaust ventilation system was chosen for the case studied. According to analyses, it is evident that both the omission of the heat recovery effect of infiltrating/exfiltrating air and using the constant exfiltrating airflow rate tend to overestimate the calculated heating load compared with the actual heating load. Finally, thermal analyses are carried out on a house with so- called dynamic walls.
Original language English Doctor Degree Helsinki University of Technology Seppänen, Olli, Supervisor, External person 26 Apr 1993 Espoo VTT Technical Research Centre of Finland 951-38-4252-5 Published - 1993 G4 Doctoral dissertation (monograph)

## Keywords

• thermal analysis
• coupling (process)
• building components
• building envelope
• structures
• buildings
• energy consumption
• heat transmission
• air tightnes
• heat transfer
• air low
• leakage
• development
• numerical analysis
• computer programs
• simulation
• convection
• models
• theses

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