Impact of Turbulence on the Thermal Comfort of Passengers in Car Cabins

Abstract

People spend a considerable amount of their time in vehicles. Hence, thermal comfort is an important argument in terms of the competitive edge. Most studies characterize thermal comfort in car cabins based on EN14505 (ENISO, 2006) originating from the evaluation of thermal comfort for low-velocity ventilation of rooms and buildings. However, the ventilation in cars is typically realized by means of high-momentum air flow through air outlets on the dashboard. In addition, the temperature sensation differs between cars and buildings due to e.g. the activity level or the environment. The aim of this study is to verify the impact of draft on the thermal comfort of passengers. The measurements are performed within a temperature-controlled environment housing a generic single-person car cabin. The latter features two air inlets with adjustable turbulence intensity and an air flow directed at the chest of a thermal manikin (TM) with a heat release of 75 W. The TM’s surface temperature (TS) is recorded by means of infrared (IR) thermometry for various combinations of inlet and ambient temperature, air velocity near the TM’s chest, and low (LT) and high turbulence intensities (HT). Based on (ENISO, 2006), the equivalent temperature (TEQ) of the different body parts is determined as objective criterion and rated accordingly. A sample result for an inlet and ambient temperature of 23°C and a velocity of 1.25 m/s near the chest is depicted in Figure 1 with (A) representing the TS of the TM for LT. TEQ for the LT scenario is shown in (B) and for HT in (C). For LT, significantly higher values for TEQ are obtained compared to HT. Here, the higher turbulence of the jet hitting the TM’s surface leads to an increase in the heat transfer and as a consequence to lower TS. At the conference, we are going to present the impact of draft on the thermal comfort as a function of air velocity, temperature and radiation.