Modeling of heat transfer in rooms in the Modelica “buildings” library

This paper describes the implementation of the room heat transfer model in the free open-source Modelica “Buildings” library. The model can be used as a single room or to compose a multizone building model. We discuss how the model is de-composed into submodels for the individual heat transfer phenomena. We also discuss the main physical assumptions. The room model can be parameterized to use different modeling assump-tions, leading to linear or non-linear differential algebraic systems of equations. We present nu-merical experiments that show how these assump-tions affect computing time and accuracy for se-lected cases of the ANSI/ASHRAE Standard 140- 2007 envelop validation tests.