Abstract
The circulating cooling water system is widely used in various industrial production fields, and its operating cost largely depends on external factors, such as ambient temperature and working medium flow. Considering the relative elevation of the heat exchanger, this study establishes a total system operation cost analysis and optimization model based on the superstructure method. The model uses ambient dry bulb temperature, ambient wet bulb temperature, and working medium flow as random variables. Water supply temperature is adopted as the decision variable, and the minimum operating cost of the system is used as the objective function. An analysis of the effect of the three random variables on the operation cost shows that the effect of ambient dry bulb temperature on the operation cost is negligible, and the effect of ambient wet bulb temperature and working medium flow on the operation cost is significant. In addition, a control equation of water supply temperature is established to determine the “near optimal” operation, which is based on the correlation among ambient wet bulb temperature, working medium flow, and optimal water supply temperature. Then, the method is applied to a case system. The operating cost of the system is reduced by 22–31% at different times during the sampling day.
Highlights
The cooling water supply temperature can be connected in series with the operation plan of each module of the system, it is used as a decision variable
An operation cost analysis and optimization model based on the superstructure method is proposed through an in-depth analysis of circulating cooling water system (CCWS)
The model considers the effect of the installation height of the heat exchanger when calculating the operation cost of the water pump (Equation (15))
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Studying the impact of changes in ambient temperature and working medium flow on the operation cost of CCWS is crucial. With regard to reducing energy use in CCWS, early researchers mainly optimized the design of the heat exchanger and water pump networks by using pinch point technology and the mathematical programming method. The authors in [17,18,19,20] considered the thermodynamic and hydraulic coupling of the cooling tower, pump, and heat exchanger units but did not describe the impact of ambient temperature and working medium flow changes on system operation. With regard to the impact of ambient temperature change on CCWS, researchers have devoted much attention to the effect on the performance of the cooling tower unit. The operation of the case system is optimized in accordance with the actual ambient temperature and working medium flow
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