Energy reduction of split-type air conditioners using a pre-cooling system for the condenser

Abstract

In the residential sector in Thailand, the largest source of energy consumption is air conditioning systems, particularly in summer as a reason of the high ambient temperatures. These high ambient temperatures affect condensers and result in low efficiency for the rejection of the heat out of the refrigerant. Moreover, air conditioning systems remove moisture from the air conditioning space due to the moisture in the air being condensed at the evaporator. This problem has led to a reduction in air conditioning systems using the condensed water to pre-cool the condenser. This study investigates the potential of reducing the energy of split-type air conditioners. We investigate the heat rejection from the condenser with a pre-cooling system compared to a traditional condenser. The result of the heat rejection from the condenser is extended to investigate the multiple linear regression model for future work. The pre-cooling system uses a wasted condenser coil to reduce the air temperature before entering the condenser. A commercial split-type air conditioner is used in this study since this type is the most used in Thailand. An ultrasonic humidifier is also installed to maintain the relative humidity at 70%RH in all testing conditions. The thermostat set points are 25, 26 and 27 ºC as the testing conditions. Each thermostat set point is tested using the pre-cooling system in the air conditioner and the traditional air conditioner. In total, six conditions are performed. The result shows that the pre-cooling system in the air conditioner can reduce the energy consumed by the air conditioner. The maximum energy reduction is 26.6% when used the pre-cooling system in the air conditioner is compared to the traditional air conditioner. The maximum heat rejection of the condenser using the pre-cooling system in the air conditioner is 74.3% higher than the traditional air conditioner. The multiple linear regression models and the coefficient of determination are reported. Finally, we conclude that the pre-cooling system in the air conditioner using removed condensed water to reduce the ambient air temperature before entering the condenser can reduce the energy consumed of split-type air conditioners and can be improved in future work.