Conference article

Split air conditioning units are usually used for small and medium scale residential buildings. Therefore; more energy efficiency and lower cost are needed along with reliable control for the air conditioning units. An experimental investigation has been carried out to study the performance of a direct expansion air conditioning (A/C) unit having a variable speed condenser fan. The modulation of heat rejection airflow has been controlled with the outdoor air temperature via a Proportional Integral Differential (PID) controller. The control algorithm allows increasing the speed of condenser fan with the increase of outdoor air temperature and vice verse. The maximum rated air flow of the fan is 0.43 m3/s at 42ºC outdoor air temperature and the minimum is 0.28m3/s. To facilitate variation of refrigerant flow rate according to the evaporator load; the traditional capillary tube was replaced with a suitable thermostatic expansion valve and liquid refrigerant reserve. The influence of condenser airflow and its temperature on the A/C unit performance and compressor power consumption has been investigated and presented at different evaporator cooling load. It has been found that a 10 % reduction in compressor power consumption is achieved by increasing the condenser air flow by about 50%.

Split air conditioners; A/C unit performance; Variable speed condenser fan