Volume 53

Effect of operating and surrounding conditions on cooling load of air conditioned cars Snehangshu Mondal, Akash Kumar, Maddali Ramgopal, Siddhartha Mukhopadhyay

Abstract

The demand for air conditioned cars has been increasing at a rapid rate due to increasing standard of living and adverse climatic conditions. The heating, ventilation and air conditioning system can reduce the fuel economy of a mid-size conventional vehicle by as much as 20%. Depending on the capacity of the air conditioning system and drive cycle, the range of Electric Vehicle (EV) and fuel economy of Hybrid Electric Vehicle (HEV) can reduce by approximately 40% under normal air conditioning loads. Thus, it is a challenge to maintain thermal comfort of the passengers and driver with minimum energy consumption. Hence proper indoor environment management of the passenger vehicle is of high priority. Thus, proper design, selection and operation of the car air conditioning system play an important role. The first step in this direction is proper estimation of cooling load on the car under various operating and environmental conditions. The aim of the present study is to develop a simple cooling load calculation model suitable for stationary and running conditions of a passenger car and study the effect of parking and operating conditions on the cooling load. The variation of cooling load of the running car is analysed by varying car speed, time of the day etc. Similarly, for the parked car the parametric analysis is done with respect to orientation of the car, exterior colour of car, ground reflectivity of parking zone base materials etc. Results show that there is 10% reduction in sensible cooling load as the car speed varies from 20 to 75 kilometers per hour. Choice of insulation material of car can affect the cooling load by about 3 %. The external colour and parking place ground reflectance can affect the heat transferred by about 14%. The heat transfer rate on the car reduced by 22.5 % when a white car with tinted glass at side windows and rear windshield, is parked on grass base, compared to a black car with normal glass parked on concrete base. It is expected that this study is useful in design of the energy efficient cars through suitable design and operating interventions.

Keywords Air-conditioned cars, Cooling load, Ground reflectance, Car speed, Solar radiation