Two-Step Methodology for Retrofit Design of Cooling Water Networks

Abstract

Conventional cooling water networks usually operate in a parallel configuration. Converting a parallel design to a series arrangement can yield a significant reduction in fresh cooling water consumption because of water reuse. This paper presents a two-step methodology for retrofit design of cooling water networks. The proposed methodology can convert a parallel configuration to a series arrangement without investment in a new heat-transfer area. The series arrangement is assumed to contain two heat exchangers. The first heat exchanger in the series arrangement is designated as the supplier because it supplies reuse water to the second heat exchanger, which is called the receiver. To retrofit a cooling water network with a parallel arrangement of several heat exchangers, the first step of the methodology uses the concept of flow rate difference curve to classify the heat exchangers into the two categories of supplier and receiver. In the second step, receiver sensitivity graphs provide guidelines for systematic matching of the suppliers and receivers. A case study is presented to illustrate the practical utility of the two-step methodology.