Study Of The Energy Saving Optimization Control Strategy For The Terminal Equipment Of The Central Air Conditioning System

The rapid increase of energy consumption of central air conditioning system is due to the constantly strengthen of the public health consciousness as well as the continuously improvement of comfort requirements. In the background of increasingly prominent in the energy shortage problem of the world along with China’s imminent policy of energy-saving, It has become the focus of attention of the industry peers that how to reduce the energy consumption of central air conditioning system on the basis of comfortableness. The terminal of the central air conditioning system is the most direct component to reflect how well the system works. Research shows that, the operation energy consumption of terminal equipment, which is up to 1/3of energy consumption of the central air-conditioner, is higher than that of chilled water pump, cooling water pump and cooling tower energy. Effectively reduction of operation energy consumption of the terminal equipment will make great contribution to energy saving of the air conditioning system.At present, the control method of variable chilled water flow is widely used in the energy saving operation of terminal equipment. While, with the continuous improvement ofthe precision degree of control systems and control modes, the control of the terminal equipment of central air conditioning system has changed to be combined withair flow control mode, not the original control mode of variable chilled water flow alone. Then, more stable and rapid adjustment to conditioning rooms can be realized. However, there are many problems in the process of heat transfer between frozen water and air in the surface cooler. For example, the process is complex,the coupling degree of the variables is high and it is much difficult to realize the physical decoupling. The existing research on thesimultaneously adjustment of chilled water flow rate and volume of air is few. To influence the heat transfer and air condition of the surface cooler by regulating the chilled water flow and air flow andlet the air conditioning room rapidly reach thermal comfort environment, the problem of coupling between the flow rate of chilled water, air flow and the heat exchange must be solved.Beginning with the control of terminal equipment of central air conditioning system, aiming at the characteristic of big time constant gap of heat transfer process between thesurface cooler and the air conditioning room, this article establishes the physical and control model ofthe terminal of air conditioning system according to the law of energy balance andconservation of mass.It establishes the simulation model of the terminal equipment of central air conditioning system by using the simulation software of Matlab/ Simulink, and finds the influence of cooling water flow and air flow on the heat transfer of the surface cooler combined with the characteristics of the coil. Then,a optimal control strategy of adjustthe frozen water flow and air flow with dual loop control method can be proposed, which can achieve the decoupling of heat exchanger of the surface cooler with the control method of single variable. Finally, to the central air-conditioning terminal system, make a simulation comparative study on the response characteristics of the air conditioning rooms’ temperature under different control modes. Results show that, the double feedback control mode with the cooling water flow and air flowad justing at the same time makes shorter adjusting time and less overshoot, which effectively improves the control performance of the system.