Numerical Analysis of Energy Efficiency of Zone Control Air-Conditioning System for Electric Vehicle using Numerical Manikin 2013-01-0237

During air heating in winter, the air-conditioning system of an electric vehicle draws much energy from the battery, which significantly shortens the vehicle's cruising distance as compared to an air cooling in summer. In this study, which considers the air-heating mode, a zone control (ZC) air-conditioning system is developed with the goal of achieving energy savings. The ZC system, which focuses particularly on the area around the driver, is able to reduce the supplied airflow rate. While this rate is one of the most important parameters in the analysis in this study, it represents a trade-off with the thermal comfort of passengers. Thus, the standard new effective temperature (SET*) is also evaluated, using numerical manikins, to compare the developed system with a conventional system.

In addition, the age of air is investigated in order to quantitatively evaluate the air distribution efficiency of the ZC system. The age of air refers to the average time it takes for air to travel from the supply outlet to an given location in the vehicle cabin. A small value indicates that the supplied air can reach a given point in a short time, i.e., with less mixing, so the supplied air temperature can be maintained. The supplied air must be delivered before it mixes with the air in the car cabin in order to ensure the system's energy efficiency.

The ZC system performance is evaluated under varying conditions- i.e., the locations of the supply outlets, the airflow directions, and the under-seat conditions-by using a computational fluid dynamics (CFD) simulation. The results show that the supply conditions are quite sensitive, and that the ZC system can provide SET* of the same level as that by a conventional system, even when the amount of supplied air is decreased by 50%.