Operational Heat Balance Model with Parameterized Geometry for the Prediction of Car Cabin Heat Loads

The paper presents the development of a mathematical model and a simulation tool for the transient prediction of the indoor climate and the heat loads in a car cabin, under real operating conditions. The main objectives were to develop a tool which facilitates, for example, the design of a cabin HVAC system or an on-line control. The model is based on the energy balance between the cabin and the outdoor environment accounting for conduction, convection and shortwave and longwave radiation. Inside the car cabin, the heat exchange is calculated between the human body, the air zone, the interior cabin surfaces and the incoming air from the HVAC system. The heat balance model assumes a simplified 3D geometry of a cabin, which is specified by seven basic parameters. The model also allows simulating the incidence angle of the sun rays onto the individual parts of the exterior surface during parking as well as during a journey. The model was tested and evaluated for a Škoda Felicia Combi car in situations of summer parking and an autumn journey. Measured data were used both as boundary conditions for the model and as validation and calibration data. The air temperature inside the car cabin, predicted by the model, was in a very good agreement with the measured mean air temperature. The model is able to correctly predict the indoor cabin air temperature and the heat loads into the car cabin, thus it is well suited as a software support tool in the process of HVAC design and on-line cabin climate control.