Analysis of duct systems for variable ventilation flow rates.

Ventilation systems using variable airflow are useful in urban areas. Due to outdoor pollutionand the indoor load from pollution or thermal sources, it is important to vary the airflow. Thismust be done without disturbing the control of the total distribution. To analyse suchproblems, there is need for a design aid. This paper presents a first version of a modularsimulation program working in the IDA environment. The program is based on a set ofindividual component-models in the NMF (Neutral Model Format) language. To illustrate theusefulness, a first series of simulations of a supply air system with the main characteristics ofa real office building, using two different control strategies is presented. To compare thecontrol strategies, a test sequence of changes in the heat load of the rooms is created. Usingthis test sequence, it is possible to detect a difference in performance of the control systemsregarding stability, ability to maintain a constant value, and ability to avoid interactionbetween separate controllers at different p m of the duct system.