Abstract

A dynamic model of a radiant floor heating (RFH) system useful for control analysis is developed. The overall model consists of a boiler, an embedded tube floor slab and building enclosure. The overall model was described by nonlinear differential equations, which were solved using finite numerical methods. The predicted responses from the model were compared with published experimental data. The comparisons were made covering a wide range of weather and operating conditions under several different control strategies. The model predictions compare well with the experimental data. The effective thermal capacity of the floor slab was found being an important parameter in calibrating the model results with the experimental data. Three different control strategies for improving the temperature regulation in RFH systems are proposed. These are: a multistage on-off control, an augmented constant gain control (ACGC) and a variable gain control (VGC). Simulation results show that the multistage control maintains zone air temperature close to the setpoint better than the existing on-off control scheme does. Likewise, ACGC gives good zone temperature control compared to the classical proportional control. A model based approach for updating the controller gains of the VGC is proposed. Both ACGC and VGC are shown to be robust to changes in weather conditions and internal heat gains. The advantage of the control strategies proposed in this thesis is that they eliminate the use of outdoor temperature sensor required in some existing control schemes. Being simple and robust, the multistage control scheme with two stages and the ACGC are good candidate controls for RFH systems.