A Methodology for Temperature Control during Blending Operation in an Automobile HVAC System without Using Heater

The heating, ventilating and air-conditioning (HVAC) system maintains thermal comfort inside car cabin. The thermal comfort to the occupant is achieved either by cooling, heating or blending the hot and cold air stream. The hot air stream is generated by blowing air over the heater mechanism (conventional coolant type or PTC heater). The design of efficient HVAC system is the fine balance between thermal comfort all along the year with varying weather conditions and at minimum power consumption. Air-conditioning system can significantly impact fuel economy of conventional vehicles, hybrid electric vehicles (HEV) and range in case of electric vehicle (EV). In the modern EVs electrically operated heater consumes substantial battery power which may adversely affect the vehicle mileage. While using such electrical heater at extremely cold ambient condition is necessary, for certain air blending conditions, usage of the electrical heater can consume the battery power which if conserved, will contribute in improving vehicle mileage. This paper presents an innovative method of air blending without using heater. This is achieved by providing an air by-pass valve and ducting arrangement parallel to evaporator. During the blending operation, the bypass valve regulates certain percentage of ambient air to mix with conditioned air at evaporator outlet. With the help of a case study and 1D CAE simulations, this paper attempts to evaluate effect of different air mixing ratios on air temperature at evaporator out.