| Mixture heat exchanger had a wide and important application in the secondary loop of nuclear power plants. Mixture heat exchanger, including deaerator, start expanding vessel, in which the changes of thermal parameters had a great influence on the safe operation of nuclear power plants. When the structures of the equipment or the heat transfer modes are not the same, the heat transfer capability of the equipment is different, and the thermal parameters are not the same. The mixture heat exchanger model established by the energy balance method could not reflect the differences between the equipment structures, the heat transfer modes and the working processes, moreover, the calculation was rough, and it couldn’t get a high accuracy.In this paper, based on the structure and heat transfer mode,the models of deaerator with spring activated shut-off nozzles and trays, deaerator with atomization nozzles and bubbling pipes, and start expanding vessel would be built. Through the analysis of the working principle of spring activated shut-off nozzles, atomization nozzles, trays and bubbling pipes,this paperanalyzed the different equipment specifically and calculated the heat transfer coefficient by a proper way. According to the form of water or steam ejected out from the equipment, the steam-water contact areas are calculated, so as to the heat exchange areas.When the boundary parameters were out of the application range of the empirical formulas,the model could switch to the energy balanced model to guarantee the application range of the model. The method of correcting the heat transfer coefficient for non-condensable gases in references was used in this paper. And the model of oxygen solubility in feed water was built by the empirical formulas based on the partial pressure of oxygen and the temperature of water, which were offered by a foreign researcher.The actual size of the device and operation data were substituted to models to verify the steady-state simulation results of the model in different conditions. The testing methods of model under dynamic-state were given in the references, including changing the mass flow of water or steam flown in or out,and theoretical analysis was carried out on its results.This paper got the simulation results of different kinds of equipment in different steady-state operations,and also got the simulation results under different dynamic-state operations. Compared withthe actual operating data or designed data, the simulation results have a high accuracy; through analyzing the dynamic-state operations in theory, the dynamic-state simulation results are consistent with the theoretical analysis and could show the influence of structure and the way of heat transfer in actual equipment. |
