The Strategy Of Control And Operation For Air-Conditioning Chilled Water System

The chilled water system plays the key role in the heat transportation of HVAC system. It operates at part-load condition in most of the time and consumes large amounts of energy as well. Therefore optimizing the control of chilled water system will yield a big progress to improve the indoor environment and to reduce the energy consumption of air conditioning system.In this thesis, a mathematical model of an actual primary-secondary pumping water system was set up. In order to provide some advices on design, selection and operation administration for the variable frequency control of primary-secondary pumping water system, the influence factors and the possibly occurred situation in its operation were researched and analyzed by means of theoretical analysis and digital simulation.The control method is the main factor for its operation performance. The stability, response characteristic and energy consumption of the HVAC system with two common variable frequency control method, by pressure difference and by temperature difference, were compared. Besides, the limitation of each method was pointed out as well.With a certain control method, the selection of controls parameter is another factor for the operation performance. Base on a variable frequency system controlled by pressure difference, the reasonable pressure difference set-point and two methods with variable set-point were presented in this thesis. Meanwhile, the influence of sensor deviation on the chilled water system is also discussed. And it is concluded that the sensor deviation shall be count into set-point when the operating situation varies a lot.Finally, the HVAC system itself affects its operation in some extent. So several different combinations of secondary pumps were simulated and analyzed. And some advices were given.