Fan-independent air balancing method based on computation model of air duct system

Abstract

This paper presents a novel fan-independent air balancing method based on computational model of air duct system. The method involves five procedures: 1) model formulation, 2) data acquisition, 3) parameter identification, 4) balancing calculation and 5) adjusting implementation. The duct network model consists of models of components like fans and conduits and assembles them by the conservation laws. Instead of using parametric model with constant parameters, the fan is re-modeled as a variable pressure source. The supply pressure near the fan outlet is measured in addition to the conventional measurements of pressures and airflows at the terminals. A model identification algorithm is designed to estimate both duct model parameters and fan pressure. The optimal damper positions corresponding to the desired airflow distribution are computed by the obtained model. In this way, damper adjusting strategies are generated by the computing results where a novel indicator is introduced to handle variations of fan pressure. The performance of this method is validated in a simulated duct network system with eight terminals. The results show that modeling fan as variable pressure source can achieve balancing accuracy within 2% error. Comparing to the previous method base on parametric fan model, this method has advantages of better accuracy, stronger robustness and higher efficiency under various conditions of fan characteristics and disturbances.