Integrated Energy-efficiency Optimization Of Central Air-conditioning System Based On The Heat Transfer Model

At present in our country, the energy consumption of air conditioning system has occupied a large proportion in the building energy consumption. And most of the air conditioning systems are always at the part load in most of the time. In this condition, the thermal efficiency is much lower than the rated capacity efficiency which leads to a large amount of energy wasted. So optimization on the central air conditioning system has important significance to relieve energy demand. Because of the central air conditioning systems is huge and complex, in order to realize the energy saving of central air conditioning system and efficient operation, optimized control effect on the part is not ideal and the entire system must be considered. In view of the overall optimization on the central air conditioning system is very less and considering the global viewpoint, energy efficiency optimization method based on the heat transfer model of the central air conditioning system was researched. It is hoped to be able to reduce the total energy consumption and efficient operation. The innovation and contributions of this thesis are as follows:1. A simplified heat transfer model of fan coil is established for wet condition. Based on a wet-dry transformation method, the wet cooling condition was converted to an equivalent dry cooling condition of the fan coil. Eliminate the effect of overall heat transfer coefficient from dehumidifying coefficient. And this also omitted the calculation process of air properties in wet conditions, did not involve the enthalpy calculation. Then the heat transfer model was simplified that could be determined only by several independent variables. The simulation results showed that the model has good precision under different working conditions.2. The optimal operation model of central air conditioning system was established. The overall system energy consumption was set as the optimization target which express as the sum of energy consumption of main components. On the basis of this, energy consumption model of the major energy components was set up and the analysis of the factor of energy consumption was carried out. Then the optimal operation parameters and the range were determined.3. According to the feature of optimization model, an improved Genetic Algorithm based on interspecies competition using adaptive crossover technology was presented which is used to the optimization calculation of the central air conditioning system. With satisfying the cooling load, the technology reduced the total energy consumption of central air conditioning system, and ensured the efficient operation. On the basis of Standard Genetic Algorithm, the improved Genetic Algorithm based on interspecies competition and integrates adaptive crossover technology to ensure solution's convergence and distribution, thereby enhance its ability of local and global search. Apply the improved genetic algorithm on the central air conditioning system optimization and the optimization results show that compared to the fixed temperature mode and small flow with large temperature difference mode, this technology can significantly reduce energy consumption of the overall system and improve the running efficiency of the system.