A METHODOLOGY FOR INTEGRATED BUILDING - HVAC SYSTEM THERMAL-ANALYSIS

This paper presents an integrated methodology for thermal analysis of buildings and their HVAC systems. The methodology is based on the use of Laplace transfer functions for the building, its heating-cooling sy stem and control components. These transfer functions can be used for building thermal control studies, frequency domain analysis and energy analysis. Laplace transfer functions for the building are obtained by means of thermal network models that include both distributed paramet er elements such as thermal mass, lumped elements such as the room lig ht-weight contents, and which represent radiant exchanges accurately. For detailed models for which an analytical solution is not feasible, the s-domain transfer functions are obtained through a modified least squares polynomial fit to the discrete frequency responses obtained by inversion of the system admittance matrix. Fourth order polynomials p rovide accuracies of approximately 1%. The methodology is applied to o btain both air temperature and operative temperature transfer function s. Laplace transfer functions are also used for HVAC system and contro l components. Transient thermal control studies are performed by means of an efficient numerical Laplace transform inversion technique. Buil ding heating/cooling load calculations are performed by means of discr ete Fourier series techniques.