Chilled water plant optimization based on part-load cooling tower performance

Cooling towers are often used in air conditioning applications to reject heat into the atmosphere. For many people in the industry, the thermal performance of cooling towers is often taken for granted. With proper control of condenser water temperature from the cooling tower, up to a 27% increase in efficiency of a central chilled water plant can be realized. The condenser water system for a chilled water plant usually consists of three major components: water chillers, cooling towers and circulating water pumps. The chilled water plants overall efficiency and performance varies continuously throughout the days operation depending on several parameters, one of which is the thermal performance of the cooling towers. The thermal performance of a cooling tower depends on the air and water flow rates, ambient wet bulb temperature and the entering and leaving water temperature. The objective of this research is to optimize the condenser water system to provide maximum plant efficiency during part-load conditions. To achieve this, a computer model was developed to assess the optimum power consumption of a central chilled water plant under various cooling loads and ambient temperature conditions by varying the leaving condenser water temperature. Simulations using the algorithms showed that it was able to predict the heat duty of a cooling tower within 2% of the manufacturers rating data. With proper control of the cooling tower up to 27% increase in the efficiency of a central water plant was demonstrated.