Abstract
Thermal environment in a vehicular cabin significantly influence drivers’ fatigue and passengers’ thermal comfort. This environment is traditionally managed by HVAC cabin system that distributes air and modifies its properties. In order to simulate cabin thermal behaviour, amount of the air led through car vents must be determined. The aim of this study was to develop methodology to measure airflow from the vents, and consequently calculate corresponding air distribution coefficients. Three climatic cases were selected to match European winter, summer, and spring / fall conditions. Experiments were conducted on a test vehicle in a climatic chamber. The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times. To be able to evaluate precision of the method, the airflow was determined at the system inlet (HVAC suction) and outlet (each vent), and the total airflow values were compared. The airflow was calculated by determining a mean value of the air velocity multiplied by an area of inlet / outlet cross-section. Hot-wire anemometry was involved to measure the air velocity. Regarding the summer case, total airflow entering the cabin was around 57 l s -1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment. The remaining cases had the same total airflow of around 42 l s -1 , and the air distribution was focused mainly on feet and windows. The inlet and outlet airflow values show a good match with a maximum mass differential of 8.3 %.
Highlights
Europeans spend significant amount of time indoors in buildings and vehicles [1]
The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times
Total airflow entering the cabin was around 57 l s-1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment
Summary
Europeans spend significant amount of time indoors in buildings and vehicles [1]. Proper indoor microclimate in relation to air quality, thermal comfort and other factors is important [2]. Inappropriate thermal environment has a negative impact on drivers’ fatigue and focus. Microclimate in vehicles is managed via HVAC (Heating Ventilation and Air-conditioning) system. The HVAC system provides defogging or defrosting of windscreens, creating conditions for safer driving. These all HVAC features are achieved through smart distribution of the air with an appropriate air speed, temperature and humidity
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