Performance evaluation of a central air conditioning system using condensate as a discharge line cooler

The energy consumption by central air conditioning (A/C) in a building is very high and efforts to reduce this energy consumption is ongoing. This study investigates the use of condensate produced by the evaporator inside the air handling unit (AHU) to cool the compressor discharge line. A central A/C with a direct expansion (DX) system and a compressor capacity of about 25 HP which uses R22 as a working fluid was used. The discharge line has a diameter of 15.9 mm wrapped with a 520 mm long heat exchanger with diameter 50 mm. The condensate produced by the AHU is passed to the heat exchanger that envelops the discharge line. The use of discharge line cooler could reduce the input power from 18.21 kW to 17.54 kW. On the other hand, the cooling capacity increased from 46.44 kW to 49.11 kW. This means that discharge cooler reduces the input power by 3.8 % and increases the cooling capacity by 5.7 %. As a result, the COP increases by 9.8 %, from 2.5 to 2.8. The method developed is not complex and only simple modification is required, thus an improvement of the performance of a central A/C system can be achieved.