9 - Sustainable design of cooling water system

Abstract

A cooling water system requires a large amount of energy and water to fulfill the cooling duty of industry. It contains two subsystems, namely a cooler network and a pump network. In a conventional cooling water system design, a cooler network is in pure parallel structure, and all the pumps are designed with the same supply pressure head. This kind of conventional design will result in larger water flow rate and higher pressure drop, leading to higher water and energy consumption. In addition, the interaction between the two subsystems has not been considered in previous research. In this chapter, a parallel-series structure is applied in cooler network to reduce water flow rate, and a main-auxiliary pump network, multiloop structure is applied in pump network to reduce energy consumption. The intrinsic relationship between the cooler network and pumping system is investigated. The model is formulated as a mixed-integer nonlinear programming (MINLP) problem. The objective is to determine the cooling water system by minimizing the total annual cost. Finally, air coolers are involved in the study to find optimal heat duty distribution between water cooling and air cooling in different conditions.