Optimal MIMO Control System Design for Direct Expansion Air Conditioning System

Abstract

Direct expansion (DX) Air conditioning (A/C) systems are widely used in commercial and residential buildings as these are more efficient and less costly than chilled-water A/C systems. In the DX A/C systems air is directly cooled by the refrigerant within the heat exchangers coils but in chilled water-based A/C systems first water is converted into air and then air is cooled by cooling coils then this chilled air is used for cooling the desired indoor thermal environment or room. For a suitable control, a MIMO controllable mathematical model of DX A/C systems is presented in this thesis. Based on the mathematical model a MIMO optimal control strategy is designed which efficiently control both indoor air temperature and indoor humidity at the same time by changing the compressor speed and supply fan speed. The simulations are done in MATLAB/Simulink environment. The simulation results show the efficacy of proposed MIMO optimal control technique regarding efficiency and improvement in thermal comfort of the room. In the future, Optimal MIMO control method can also be used for the other Heating Ventilation and Air conditioning systems (HVAC) to enhance their efficiency and performance.