Guided design of heating and cooling mains for lower water and energy consumption and increased efficiency

Abstract

Water cooling and water heating is an important source of energy consumption, accounting for more than 20% of all energy consumption in manufacturing industry. It is clear that the development of heat recycling schemes and better structural design can allow reaching significant savings. It is also known from power generation and from the bulk chemicals production that the cooling water systems are generally designed with a set of heat exchangers arranged in parallel. This arrangement results in higher cooling water flowrate and low cooling water return temperature thus reducing cooling towers efficiency. This indicates the importance of the system structure, the possibility of mixing of heating or cooling water; recycling and reuse of heating and cooling resources and finally the importance of distribution of the driving forces to heat transfer. This paper reports a technique for grassroot design of centralised cooling and heating water system for water and wastewater minimization which incorporates the performances of the cooling/heating providers involved. The study focuses on cooling/heating systems consisting of multiple chillers and/or boilers that supply a common set of heat exchangers. The paper takes a conceptual approach to the stated problems, but traces the way for exact solution using the superstructure based mathematical approach (formulating the problem). It explores cooling/heating water reuse opportunity and predicts thermal performance of thermal systems involved.