| With the rapid development of urbanization in China,the scale of construction industry is expanding.As we all know,a considerable part of the energy consumption of public buildings is consumed in air conditioning systems,the air conditioning systems have great potential for energy conservation.Studying the overall hydraulic characteristics of the chilled water system and optimizing the control and operation of the chilled water system are effective ways to achieve energy saving in the air conditioning system.This dissertation takes the energy saving and consumption reduction of chilled water distribution system as the entry point,and takes the effect of reducing “large flow and small temperature difference” as the guideline.Simulation and testing are the main research methods.The air-conditioning water system experiment bench and its automatic control system were set up.The simulation platform of the air-conditioning water system was established and the Matlab code was written.For on-off chilled water systems,consider the system hydraulic balance and system hydraulic imbalance.the influences of the opening and closing of fan coils in different positions and the total opening ratio of fan coils on to the flow and hydraulic imbalance of other fan coils,total system flow,and the user-side drag coefficient of the system were studied.When the total opening ratio of fan coils is < 40%,the total opening ratio will have a bigger impact on the user-side drag coefficient of the system and at the same time,the distribution of the fan coil open position has begun to show the influence of the user side drag coefficient of the system.A method for determining the range of change of the operating condition of the fan-coil random opening system is given and comparison of two different hydraulic balance systems operating conditions.For continuously regulated chilled water systems,through air-conditioning water system experiment,Analysis the variation of the overall hydraulic characteristics of the experimental bench,In addition,verified that the dynamic pressure differential valve has good regulation characteristics.Through The simulation platform of the air-conditioning water system,the influence of the opening change of single AHU valve on the flow of other AHUs,the total flow of the system,the user side drag coefficient of the system,and the influence of different pressure control positions on the system flow distribution were simulated and analyzed.Based on the overall hydraulic characteristics of chilled water,the corrective principle of chilled water system control was pointed out.A “variable pressure difference control method based on combination of load distribution and pressure difference control point correction method” and “variable pressure difference control method based on combination of the most unfavorable hydraulic loop and most unfavorable thermal loop” have been proposed.Through the simulation analysis,the selection principle of differential pressure control differential pressure setting value for several typical operating conditions of the pump is given.A dynamic simulation and calculation platform for hydraulic and thermal coupling of a short time step air-conditioning system was established.Through a specific case simulation,analyzing the overall hydraulic characteristics,thermal characteristics,and control effects of the chilled water system under on-off regulation. |
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