Sultanate of Oman witness a long summer with mostly clear blue skies and typically higher ambient temperatures as seen in other GCC countries. This type of environment warrants the use of high capacity and reliable air conditioning systems, both at resident buildings and vehicles. During summer, cars parked directly under the sun, experience a very high temperature rise inside its cabin in the range of near to 50 °C. This high cabin air temperature often causes thermal discomfort to passengers entering the parked car and also has a serious impact on the cars air-conditioning systems, as it takes longer time to bring back the thermal comfort inside the cabin. The studies also revealed that the high cabin temperature often causes health hazards to occupants, especially to infants. Current research paper, reports an experimental study carried out on a parked car, with instrumentation to identify the various the temperature zones inside the car cabin. This experiential study is aimed to improve the thermal comfort inside the cabin through solar powered cabin air ventilator for effective management of cabin air temperature. The study was carried on a chosen vehicle parked at a set direction and location exposed to day long sunlight at Muscat for considerable period of time. Firstly, the study identified the various temperature zones inside the car cabin and ventilation driven with a 10 Wp solar panel was developed to accomplish the required air exchange inside the cabin, along with continues instantaneous heat rejection through steady air exchange between inside and outside environment. A simple ventilator was developed by means of two fans which drove out the hot trapped air and a secondary fan to cool down the temperature inside the car by providing fresh air for limited time. The experimental investigation showed that the vehicle cabin temperature was typically 10 °C lower when ventilator was turned on. On a typical day on month of May, the cabin air temperatures was approximately 21 °C higher than the ambient air temperature, while with the developed ventilator the difference between the cabin and outside air temperature was reduced by 50% approximately. With the ventilator in operation, it was observed that time taken to reduce the cabin air temperature through vehicle air conditioning system to a satisfactory level was much quicker; typically it took less than the half of the time compared to those values tested without ventilator. Thus indicating, the power saving potential of the developed system as the desired level of thermal comfort can be achieved within the shorter period of time. The reduction in time taken to cool down the cabin temperature to the acceptable limits has direct two fold effects; firstly, the fuel consumption for cooling purpose is reduced and secondly, increased thermal comfort level inside the cars cabin. However, the temperature drop pattern was not similar all around the cabin, due to the varied level of cabin sunlight exposure. Temperature drop at the front of the car was lower than in middle and rear of the car. From the study it can be concluded that, with solar powered ventilator, the temperature inside the car was nearly 10 °C lesser compared to cabin without ventilator and it also helps in to bring back the thermal comfort inside the cabin nearly within half time vis-à-vis cabin without ventilation.
A multi-objective study on the operation of task/ambient air conditioning systems in subtropics
