Development of temperature controllers for a room deploying the displacement ventilation for heating, ventilating, and air-conditioning

Abstract

By employing the fuzzy control theory and dynamic matrix control method, the controllers for temperature control of a room cooled by a displacement ventilation system are developed. The fluid flow and heat transfer inside the room are calculated by solving the Reynolds-averaged Navier–Stokes equations, including the effects of buoyancy in conjunction with a two-equation realizable k–ε turbulence model. Thus, the physical environment is represented by a nonlinear system of partial differential equations. The system also has a large time delay because of the slowness of the heat exchange. Additionally, the temperature of the exterior wall of the room first increases and then decreases with time during a 24-h period, which acts as a strong disturbance in changing the temperature of the room. The goal of this article is to develop controllers that will maintain the temperature in the room within the specified upper and lower bounds by deploying the displacement ventilation system. In order to solve this temperature control problem, we develop a special fuzzy control method. At the same time, we analyze the peak value of the error and employ the dynamic matrix control method to replace the fuzzy control method with success. The results show that the fuzzy controller is effective in saving energy, and the dynamic matrix control method can contain the error within the specified bounds in the worst situation (when the temperature of the exterior wall is highest). These kinds of fuzzy control and dynamic matrix control methods can also be employed for other heating, ventilating, and air-conditioning systems such as overhead variable air volume system and radiant cooling hydronic system.