Modeling indoor CO2 concentration stratification dynamics in a ventilated room using a simplified physical model

The paper presents a simplified physical model to predict the temperature response stratification in a room with mechanical ventilation system. The model was built from theoretical analysis on the energy conservation of a three dimensional ventilated space. The temperatures of typical positions in the ventilated room were obtained for identifying the unknown parameters and order of the model. The temperatures were calculated using the transient computational fluid dynamics (CFD) simulation with changing supply air temperature. An area identification algorithm was presented to identify the model order and parameters from the CFD simulation results. The identified results illustrate that the simplified physical model can investigate the dynamic temperature responses in the ventilated room with thermal stratification rapidly and accurately with the relative error near 0.1%. The model can be used for designing a control system to overcome shortcomings of perfectly mixed models of indoor air. Therefore it can be used as a tool to optimize indoor partial zone temperature control to improve the indoor thermal comfort level reasonably.