| Absorption chillers can be driven by low grade thermal energy because it can recycle the waste heat produced by power subsystem (micro or small gas turbines, gas, fuel cells, etc.) to provide heat or cooling capacity, so it is widely used in the distributed power system. In order to study the dynamic characteristics of the distributed power system, and thus to improve the efficiency of model development, and to optimize the operation of the distributed power system, a dynamic simulation model library of distributed power system related to variety of power equipment and refrigeration equipment needs be set up urgently. The main research is presented as follows:(1) The working medium models of absorption refrigeration equipment is set up by using the Object-Oriented Modelica language which was faced to the object, including Lithium bromide solution physical model, flue gas physical model, water and water vapor properties model. Aiming at the specific requirements of dynamic simulation, different physical property calculation parameters and function expressions input different parameters were applied to with. The same kind of working medium, so the iterative computations process of physical properties is reduced. As a result, the computational accuracy and speed will be improved.(2) Based on the object-oriented concept, the absorption refrigeration system was divided into9blocks, three layers. Each block is inserted into another block, and each layer is inserted into another layer. Heat transfer model, mass transfer model and the mutual coupling mode is set up according to the flow outside the pipe. The discrete "one-dimensional staggered grid model"can be solved by finite volume method according to the flow inside the pipe. Concentrated parameter model was used on other parts like high and low temperature heat exchanger. At the same time, all kinds of sensor model is set up to detect the thermodynamic parameters of a certain point. (3) The generator parts in the absorption refrigeration model is validated to be correct, three different loop structure models of the libr absorption chiller is set up and validated. According to one effect hot water operated machine, the dynamic response of the unit to the hot water temperature, flow, cooling water temperature, flow rate and refrigerant water temperature and flow rate is discussed. Accoding to the double type flue gas model, the dynamic characteristics of refrigerator of double type flue gas under the interaction of three parameters is also discussed. The results show that the error of the absorption refrigeration models are in5%which compared with experimental values, can accurately capture the dynamic characteristics of the unit.(4) The model of a office building is set up by Simergy, and EnergyPlus is used to simulate the hourly cooling load all the year. The load is the basis of distributed energy system equipment selection, then the micro-gas turbine plus one effect of flue gas absorption refrigerating machine model of distributed energy supply system is united to be simulated. At last, the power generation and refrigerating capacity of distributed energy supply system of a typical day in summer is discussed as well as the change of COP in absorption chillers. In the process of the whole simulation, the error is10%which compared with design efficiency. The consistency with the thermal inertia is showed in mic-gas turbine and absorption refrigerating machine.(5) The PID feedback control of gas turbine is set up on Dymola, the fuel gas inflow can be adjusted with the change of the demand of user’s loads. The result shows that if the working condition is changed, the system can still be stable, accurate and rapid through the control method by PID controller, and the good dynamic characteristics can be obtained to meet the needs of the project. |
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