Each year, large quantity of fresh water is consumed by cooling water system. Installing air coolers in cooling water system leads to a reduction on work load of cooling tower and saves on fresh water. This paper gives an optimization model for formulating cooling water system with air coolers. The air coolers are used to cool down the process hot streams as well as the returned cooling water. One precooling air cooler is used to cool down the returned cooling water before the water entering the tower. Besides, branch air coolers are considered for cooling down the returned cooling water on the branches of cooler network. The cooler network, air coolers, and cooling tower are optimized simultaneously. The objective of this work is to obtain framework with minimum cost. Case study taken from existing literature is employed to show the effectiveness of proposed model. Final results indicate that introducing precooling air cooler in grassroots design problem can reduce both fresh water consumption and total cost.
