Experimental study on adiabatic pre-cooling systems for air cooled condensers in hot and humid climates

The rise in ambient temperature caused by heat waves has led to increased demand for comfort cooling that affects the operational reliability of unitary air conditioning system. This study investigates the performance of a residential air conditioning unit of 1 ton equivalent by integrating adiabatic pre-cooling systems into the air-cooled condenser in the hot and humid climate of the Chennai region. Three types of adiabatic pre-cooling methods were employed: (1) evaporative cooling (EC) pad, utilising a 100 mm-thick cellulose pad; (2) mist cooling, achieved through an ultrasonic humidifier; and (3) a combination of EC pad and mist cooling, using a reduced cellulose pad thickness of 50 mm. The study assessed energy consumption, operational performance, condensate water production, condenser temperature drop, and cost benefit analysis. An experimental analysis was conducted by varying the air conditioning (AC) set point temperatures from 24 °C to 28 °C. Results showed retrofit of EC pad + mist cooling configuration to be holistically effective in terms of payback, yielding an average energy savings of approximately 39.2% when compared to other modes. Additionally, it significantly enhanced cooling system efficiency, with a mean COP increase from 2.8 to 5.0. The hybrid precooling method also effectively reduced temperature variations across the condenser up to 2 °C, showcasing moderate effectiveness. Despite requiring water consumption management, it led to reduced condenser on-off cycling frequency, indicating improved energy efficiency and system performance. EC pad + Mist cooling led to balanced energy and water efficiency without requiring additional water sources by utilizing condensate water.