Dynamic simulation of an air handling unit and validation through monitoring data

This paper presents the model for the simulation of the behavior of an air handling unit (AHU), consisting of two heating coils, a cooling and dehumidifying coil, and a vaporizer. The proposed model reproduces the behavior of its single components, using the suitable ε-NTU relations for the heat exchangers on the basis of actual geometries (e.g., type of heat exchanger, number of tube rows, number of passes), and mass and heat balance equations for the vaporizer and dehumidifying coils. The routine is developed as a MATLAB script and it is linked to a TRNSYS model, which simulates the building. The model is applied to a real AHU, which provides fresh air for an exhibition room of a museum, varying the supply relative humidity based on the indoor set point. During a one-month monitoring campaign in the building, several data about the external and internal climate were acquired, together with specific parameters of the AHU system (e.g., temperature and water flow rate at the heat exchangers, supply temperature and relative humidity of the air flow). These monitored data were compared with the outputs of the MATLAB script, validating the AHU model in the error band of the monitoring system.