Dynamic method to calculate airflow rate with displacement ventilation

Design of displacement ventilation is usually based on a heat balance method when overheating is the primary indoor climate concern. Various models for calculating airflow have been developed for several decades. Commonly used models are based only on the stationary models. However, in practical applications, the performance of DV depends on potentially dynamic parameters, such as strength, type and location of heat gains and changing heat gain schedule. Besides, thermal mass affects dynamically changing the room air temperature. The study presents case studies of dynamic DV design for typical applications in a lecture hall. The effect of thermal mass on the indoor temperature stratification and design airflow rate calculating is studied for heavyweight and lightweight constructions. In the dynamic DV model, the capacities and conductances of indoor air and building structures are calibrated against the results taken from the advanced building simulation model IDA-ICE. In addition, the capacities and conductances are calculated theoretically with the simplified RC-model. The study revealed that the difference in the design airflow rate calculations between calibrated and theoretical models are less than 10%