Innenraummodellierung einer Fahrzeugkabine in der Programmiersprache Modelica

Aachen / E.ON Energy Research Center, RWTH Aachen University (2014) [Dissertation / PhD Thesis]

Page(s): XV, 127 S. : Ill., graph. Darst.

Abstract

The thesis describes the development of a calculation model for indoor air flows using the example of a car cabin whose temperature and velocity field are characterized by complex flow structures. For a simulation of these structures, the so-called zonal model approach offers the most reliable compromise in terms of real-time performance and the level of detail. The approach used in the work to model the enthalpy flows between individual zone requires knowledge of the current flow structures for different boundary conditions. Based on detailed CFD simulation of the air flow with different combinations of boundary conditions, the fluid transport between the individual zones is linked to the defining boundary conditions. The developed model consists of 24 zones. A simulation of the temperature distribution over the 24 zones results from a calculation of enthalpy flows between the zones, a consideration of transmission heat flows through the enclosure as well as the influence of solar radiation and long-wave radiation exchange between individual surfaces within the car cabin. The correlations between the boundary conditions and the resulting enthalpy flows between individual zones are based on the results of a limited number of detailed CFD simulations. The validity of the correlations in the zonal model is therefore limited to these cases, as well as to the dimensions of the geometry used. The model structure is developed in the programming language Modelica using the simulation environment Dymola. It allows an easy expansion with other combinations of boundary conditions and different geometries of car cabins. This text provides an introduction to the relations of thermal comfort and vehicle air conditioning against the background of gradual electrification of the powertrain. Starting with the growing importance of modeling in the automotive industry to compare climate control concepts, different approaches of modelling room air flows are presented. After an overview of existing approaches of zonal models, the parametric description based on CFD simulations is explained and different methods of zoning or identifying characteristic structures in a velocity field are presented. Chapter five describes the measurements on a test vehicle for the parameterization of individual components of the model as well as the necessary validation. Typical flow structures inside a car cabin are analyzed in chapter six. The modelling of the cabin air flow, the heat transmission to the surrounding areas as well as the short - and long-wave radiation exchange are described in chapter seven. A validation is performed for a variety of different heating and cooling cases (chapter eight). Chapter nine describes the application of the model for the determination of the energy consumption for different ventilation scenarios and glazing, as well as in combination with a comfort model for a passenger.

Authors

Authors

Flieger, Björn

Advisors

Müller, Dirk

Identifier

  • URN: urn:nbn:de:hbz:82-opus-49356
  • REPORT NUMBER: RWTH-CONV-144314