Study On Ventilation And Air Conditioning Thermal Model Experiment Of Bai Hetan Hydropower Station’s Underground Powerhouse

As the increasing consumption of the traditional energy,humans begin to explore new forms of energy. Hydroelectricity has got the favor of human for its property of renewable and non-pollution. The Bai Hetan hydropower station is the largest underground hydropower station in the world. Its civil structure and internal equipment is very complex. The paper is based on the method of model experiment, studied the ventilation and air conditioning scheme of Bai Hetan underground powerhouse. The research content and results have important engineering value.First, based on the similar theory and archimedes model law and combining the actual situation, The model experiment choose 1/20 as the similar geometry scale. According to the similar scale of the relative parameters, make the program of the model experiment of the underground powerhouse and the busbar tunnel of the Bai Hetan hydropower station. Setting up the model experiment rig and the test system.Then, made the cold state and thermal state operation test of the model, and put forward some improved recommendations. Based on the work of the operation, we make an analysis of the major problems and difficulties of the model experiment, and summarized some technical methods to improve the precious and reliability of the model experiment. 1) By the restriction of the similar model law, the air volume and thermal scale of the model is very small, usually lead to the values of the air volume and the heat is very small too. In the model experiment of small air volume and heat, the problem of the hydraulic balance 、 the problem of the heat transfer of the building envelope and the ventilating duct and the problem of the control of the temperature of the air supply are the main problems of the model experiment. 2) In the model experiment, choosing the “disperse system and big pipe diameter” as the air supply way can meet the requirements of uniform air supply and by this way can solve the problem of the hydraulic balance; Choosing the better thermal insulation material( l ≤0.036w/m·k, thickness ≥4cm) as the model building envelope can minish the capacity of the heat transmission to the range of the allowable error; By the way of putting the thermal insulation material on the outside of the main air supply duct and pass the excess air volume can minish the heat transfer and make the temperature of the air supply on the same level. The area which below the generator floor use the duct supply air, and in order to make the temperature of the inlet and outlet at the same value, we put the thermal insulation material on the outside of the air supply duct and increase the heat or cooling capacity, by this way, the temperature difference can be less than 0.1℃. Using these methods, the model experiment get an ideal result.At last, we carry out the ventilation and air conditioning thermal experiment of the Bai Hetan hydropower station’s underground powerhouse. The model experiment mainly including three parts. 1)the generator units are all running, just changing the temperature of the air supply, study the reasonable air supply temperature which is meet the design, and analysize the reasonable of the uniform air supply. 2) the generator units are all running and turn on the partial air conditioning, explore which temperature can meet the design of the whole powerhouse, and compared to the first part of the experimental results, analysize the influence of the temperature distribution of the whole underground powerhouse when the temperature of the air supply is same. 3) only turn on parts of the generator units and let parts air supply grills open, analysize the temperature distribution of the whole underground powerhouse.From the analysis of the results of the model experiment, we can make some conclusions as follows: 1)By the way of uniform air supply, we can make the velocity of the generator floor at a same level, the range of the velocity is from 0.22m/s to 0.36m/s, and it can meet the requirements of the design range value, 0.2 ~ 0.5 m/s. 2) Tunning on all generator units and tunning off the partial air conditioning, when the temperature of the air supply is at 20℃, the temperature of the whole powerhouse can meet the design value, but the tempareture of the generator floor and the busbar tunnel is lower than the design value, so it is a waste of the cooling capacity. Just change the temperature of the air supply can make an important influence on the whole powerhouse but can not get an ideal effects of some areas.3)Turning on all generator units and partial air conditiong, when the temperature of the air supply is at 21℃, the temperature of the whole powerhouse can meet the design value, only the temperature of the below volute floor has 0.3℃ higher than the design value. The partial air conditiong has a great influence on the temperature distribution of the busbar floor and busbar tunnel. So make the temperature of the air supply at 21℃, and turning on the partial airconditioning is an economic and reasonable scheme. When turning on parts of the generator units, make the temperature of the air supply at 22.1℃, because of the positive influence of the cooling effect of the rock wall, the temperature of the whole powerhouse can meet the design requirements.