Evaluation of the design of chilled water system based on the optimal operation performance of equipments

Central air-conditioning system is usually designed according to the peak load, and improper design is a popular problem. Commonly, when the central air-conditioning system is improperly designed, the operation performance of each equipment in the system will be deviated from its optimal operation performance. In order to evaluate the effects of the design of a central air-conditioning system on the operation performance of equipments and the system, this paper proposes an evaluation method based on exergy analysis. A chilled water system of a central air-conditioning system serving a building in Changsha of China is used as the study object. Based on exergy analysis, the optimal operation performance of the chilled water system and each equipment under specific load condition are obtained by maximizing their exergy efficiencies respectively. The evaluation index - operation matching degree of equipment is defined as the ratio of its exergy efficiency under system's optimal operation performance to its maximum exergy efficiency. And the operation matching degree of system is defined as the product of the operation matching degrees of all equipments in system. According to the frequency distribution of year-round load conditions, the annual operation matching degree of system is obtained, which is used to evaluate the design of chilled water system for a long term's operation. Eight alternative designed chillers and three alternative designed chilled water pumps are introduced to verify the evaluation method. By comparing the annual operation Matching degrees of chilled water system in different designs, the optimal design of chilled water system is pointed out. (C) 2016 Elsevier Ltd. All rights reserved.