The method of evaluating operation performance of HVAC system based on exergy analysis

Abstract

Abstract A simulation model of an airport terminal's the heating, ventilating and air conditioning (HVAC) system is established. Based on simulation calculation, the unit exergy cost, the object exergy efficiency and the exergy loss ratio of each component of HVAC system are obtained by the structural theory of thermoeconomics. The operation performance of HVAC system and the optimum potential of each component are analyzed by those indexes. In order to evaluate the influence of the control strategy to operation efficiency of HVAC system, a new evaluation method is presented which setting ideal operating level as the criterion, using control perfect index ( CPI ) to evaluate operation performance of the HVAC system. And the energy flow process of this HVAC system is divided into two subsystem energy flow processes (the subsystem A and subsystem B ). Evaluation results show that the annual CPI and the optimum potential of the system are about 0.77 and 23%, respectively, when the original strategy is used. The optimum potential of the subsystem A is larger than the subsystem B . Two control strategies, the optimal load allocation control strategy ( Load Allocation Strategy ) and the optimal supply air temperature reset strategy ( SAT Strategy ) are presented and analyzed by this new evaluation method. Simulation calculation results show that the annual CPI of the system with the Load Allocation Strategy and SAT Strategy are about 0.82 and 0.78, respectively. The Load Allocation Strategy can improve the operation performance of the system more greatly than the SAT Strategy . It means that the evaluation method not only can evaluate the operation performance of the HVAC system, but also can give the direction for optimal control of the HVAC system.