Passive Energieeffizienzmaßnahmen im Fahrzeug zur Reduzierung des Heiz- und Kühlenergiebedarfs

  • Passive reduction of energy consumption in vehicle air conditioning by optimizing cabin properties

Welp, Ralf; van Treeck, Christoph Alban (Thesis advisor); Müller, Dirk (Thesis advisor); Vallée, Dirk Heinrich August (Thesis advisor)

Aachen (2017)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2017

Abstract

The book on hand provides a method for evaluating different thermal passive improvements on the vehicle cabin. A thermal cabin simulation model in Modelica is developed, based on the RWTH Aachen Modelica Library “AixLib”. The model respects the cabin geometry, material properties and Heating, Ventilation and Air Conditioning is regulated by a simple PI-controller to the interior temperature. Models for surrounding conditions like weather, driving cycle or solar radiation are implemented. Main output-value is the power-consumption of the HVAC-model and the interior temperature. The whole model is validated against measurements on a real test vehicle in a climate dynamometer chamber.Within the development of the cabin-model the glass-curvature is one parameter that normally is not respected with thermal cabin simulation. Since there was no possibility to get the influence of the glass curvature for passenger car thermal cabin simulation models this parameter is evaluated in detail. Based on the known radiation properties of flat glass, a new method for calculating transmission through curved glass is developed respecting influences due to changing ray-progress in the glass and the effects of the wider projected area of curved windows. An analysis of this effects leads to a prioritization based on effect-size and all relevant influences are summarized in a set of curves. The major effort for calculating this set of curves leads to a simplification process that brings a formula depending on a normed curvature radius and the incident angle. This formula is further developed to a method for calculating the influence of curvature on radiation transmission in 3D-simulations. To evaluate the impact of the glass curvature on transmission for passenger cars, curved building facades and roofs three exemplary simulations are done, respecting the position of the sun during a whole day. The simulations indicate, that glass curvature can be neglected for normal passenger cars. For curved building facades and roofs the simulation gives evidence that glass curvature can't be ignored. The developed model is an adequate method for respecting this influence in an early state of thermal building simulation.Corresponding to the objective of this work a sensitivity analysis is performed with the developed thermal cabin simulation model. For this analysis three parameters are identified for variation: Thermal insulation of the cabin, thermal mass and solar transmission. These parameters are evaluated in three different environment conditions (warm, moderate and cold temperature). The analysis determines the solar transmission as the major parameter. Therefore window concepts with glass technologies to affect solar radiation are developed for a passenger car. These concepts are implemented and simulated in the thermal cabin simulation. The results show a significant benefit of infra-red reflecting technologies. Although switchable glass is not yet ready for the use in passenger cars due to performance issues and optical properties the thermal benefit is proven by the results.