Heat transfer and air flow in buildings

Modelling of heat propagation in buildings, consisting of rooms separated by in-ner walls and covered by outer walls, roofs, etc., belong to serious non-trivial prob-lems of civil engineering design. Especially in rooms the classical heat conduction analysis (using the Fourier-Kirchhoff approach) gives no reasonable results because the air flow, driven by outer climate quasiperiodic changes, forces quite other time-variable redistributions of a temperature field. Thus, three physical conservation principles have to be respected – of mass (generating one continuity equation), of momentum (generating three equations of viscous air flow of the Navier- Stokes type) and of energy (generating one equation of heat transfer that can be identified with certain extended version of the Fourier-Kirchhoff equation). Nevertheless, such general system is complicated and corresponding numerical calculations are slow and expensive. This paper discusses admissible simplifications and presents the original MATLAB-based software code for the analysis of simultaneous air flow and heat conduction both in rooms and in construction parts, implementable on standard personal computers without higher hardware of software requirements. One two-dimensional example with a realistic room size and air characteristics is demonstrated. Key words: building design, heat transfer, air flow, Fourier-Kirchhoff equa