Dynamic Thermal Performance and Controllability of Fan Coil Systems

In order to characterize and control a system properly, it is inevitably necessary to understand and define the interactions between various design parameters and the controllability of the system. This study experimentally investigates effects of three design parameters, including supply water temperature, fan speed, and room heat load, on the dynamic response of a fan coil system. The experiments have been performed in a mock-up of an office room equipped with a fan coil unit (FCU). A direct ground cooling system has been used to supply the FCU with high-temperature chilled water ranging between 15 and 23 °C. The dynamic response of the system to step changes in the design parameters has been studied using room operative temperature as an indicator. The results of this study indicate that the system behaves as a first-order system without a time delay. The results also suggest that the time constant and the characteristic of the dynamic response of the fan coil system are not affected by the initial room temperature. Among the design parameters, fan speed is observed to have the most significant effect on the dynamic response of the system. Supply water temperature and room heat load are both found to have insignificant effects on the dynamic response characteristics of the system.