Gebäudemodell-basierte Simulation von Raumluftströmungen 2004-07-12

  • Indoor Air Flow Simulation Based on a Building Model

van Treeck, Christoph

Munich : Shaker (2004)
Dissertation / PhD Thesis

Dissertation, Technische Universität München, 2004

Abstract

In this thesis, simulation techniques are discussed with respect to the quantification and evaluation of indoor air flows and ways of linking these techniques to a building model. The appearance of the indoor air flows is characterized by means of typical configurations of the outer shell of the building. The impact of air flows is depicted with respect to building energy consumption and thermal comfort of the user. In order to simulate the transient thermal behaviour of a building numerically, a finite volume method is described for balancing heat gains through the building's fabric. In thermal multizone models, enthalpy flows caused by pressure differences are usually computed using a single node or just a few nodes per zone. As this discretization technique restricts the spatial resolution of indoor air flows, a more detailed high-resolution CFD simulation is required in some cases to resolve local flow patterns, as shown in the preliminary study of a coupled simulation. The utilization of the coupling interface developed for this purpose is demonstrated by a coupled simulation between a commercial CFD system and a thermal multizone building model of a sample building with an inner courtyard. The results are compared to measurement data. The process of linking numerical approaches to building models is hampered by the range of different models put forward for planning and calculation purposes which reflect the conflicting views of the people involved in the design process. An ansatz based on graph theory is accordingly used to interpret the geometrical, topological and semantical data of a building product model. In order to derive a room model, a structural component graph, a graph of room surfaces, a room graph and a relational object graph are identified as aids. Algorithms are developed to derive these relations. The room model serves to identify objects semantically and derive both an object model and a surface model. This serves as a precondition for coupling dimensionally reduced and detailed approaches with respect to the simulation of thermal building behaviour. The application of the technique presented here is demonstrated by the analysis and discretization of a complex sample model. The lattice Boltzmann technique is applied to simulate convective air flows. Its extensions are discussed with respect to energy conservation and a Large Eddy subgrid scale turbulence model. Validation computations of the hybrid thermal model employed match the values from the literature well. A complex three-dimensional example based on the indoor air flows within an atrium is used to demonstrate the prototypic implementation of the method.

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