Control-oriented fan coil unit modeling for room dynamics considering dehumidifying cooling conditions and indoor air quality

Abstract

This paper studies a control-oriented fan coil unit (FCU) modeling problem, which takes into account latent heat for the process of dehumidification during cooling analyses and indoor air quality. A single-zone room model is studied by considering the thermal, humidity, and CO2 dynamics, and an FCU model is built by simulating both sensible and latent heat exchange considering three different types of conditions (completely dry, completely wet, and partially-wet-partially-dry). The process of dehumidification in the FCU is very complex and challenging to model and is affected by multiple coupling factors such as the structure of the FCU, the temperature and flow rate of air and refrigerant, etc. The proposed FCU model includes the process of heat exchange under the aforementioned conditions of the FCU so that the dynamics of room temperature and humidity can be obtained. The speed of the fan and the position of the damper inside the FCU are controlled for the integration of the room and FCU models. The simulation results show that the proposed control methods are effective in maintaining the temperature, humidity, and CO2 concentration level in the desired ranges for cooling conditions with dehumidification.

Keywords

• FCU modeling
• HVAC control
• Heat exchange
• Fan speed control
• Damper position control