Dynamic Simulation Of Air Handling Unit

Today air-conditioning systems is design to satisfy the maximum load of building, but in most of the time, it works under part-load conditions. The automatic control is very important to the regulating characteristic of air conditioning system. How to optimize the control system in order to reduce the energy consumption under the precondition of meeting the requirements of comfort is becoming a major objection to the whole world, especially developed countries and regions)Air handling units is a most important component of the host air-conditioning system . The AHU plays a role of energy exchanger which transfer the energy between the refrigeration mainframe and the air conditioning area. The running and operating character of the AHU will not only impose on the regional air-conditioning temperature and humidity but will also affect the host refrigeration load. The control of AHU is the main portion of air conditioning control system.Now many researchers focus on dynamic models of the air handling unit. And most of their research follows this kind of thinking method: establishing the mathematic model of unattached part of AHU, then giving certain supposition conditions, and using finite difference methods to solve partial equation with programs. As the development of system simulation technology, there are more simulation tools which can provide many conveniences of system simulation for study, especially the authorized simulation software matlab/simulink. This paper uses the new edition matlab platform to do some simulation research on of cooling coils , air damper , blower , mix section and the whole system on the base of unstable conditions. Then three conditions including change the status of air quality, change the status of water quality and change the temperature of water are researched to get the response of AHU under changing conditions. The response of air-handling unit under PID control strategies and fuzzy self-tuning PID control strategies are discussed using the fuzzy control toolbox. The conclusions indicate that, the regulation of the units under the condition of changing the air flow rate is greater than the impact of changing water conditioning. The quantity of heat and the export air temperature are linear to the temperature of inlet air temperature when the flow rate of air and water are fixed. Fuzzy-PID control has higher precision, smaller overshoot ,and the method has strong adaptation, robustness and disturbance-rejection especially when the parameters of the object are changed , compared with conventional PID control. The system can effectively control the air-condition system which is nonlinear, frequently variable and time-delaying.