| With the rapid development of national economy and the shortage of the fresh water, our country pay more attention to saving water. Inventions associated with evaporative condenser were imported into China dating back to 1980, and due to the advantages of high thermal efficiency, saving water and energy, compact structure and so on, is used to the refrigeration and petrochemical industry. Because there was no awareness of the importance of fresh water resources, evaporative condenser has not been used in power plants, however, in abroad, evaporative condenser has already been applied to the power plant, and achieved good results. Therefore, apply evaporative condenser to cooling system in thermal power plants has important industrial value.Evaporative condenser inherited the merits of the water-cooling system and air-cooling system, mainly using the water absorbs the latent heat of vaporization and reaches the purpose of cooling steam exhaust of steam turbine. Since evaporative condenser being used in China, its internal heat exchange tube bundles basically use different forms of round tube. Many studies of special pipe demonstrate that its heat transfer effect is superior to the circular tube, and it is gradually applied. Oval tube is one of the most used in special tubes. The application of elliptical tube in the evaporative condenser can highlight the water and energy saving characteristics of evaporative condenser. Therefore, the main purpose of this paper is to design horizontal oval tube evaporative condenser, set up test-bed and conduct the experiment. Also another aspect of this work is to reach the correlations which can provide technical support for project of large oval tube evaporative condenser and promotion and application of the power plant.By reading a lot literature about the evaporative condenser, heat transfer laws of Oval Tube and horizontal tube flowing liquid film, by analyzing the principle of evaporative condensers and referring to the relevant evaporative condensers experimental apparatus, this objective of study is to complete the design of horizontal oval tube evaporative condenser test systems for research the heat transfer laws and flow characteristics. Oval tube as the research objective, the experimental purpose is to study on flow characteristics of the steam inside the oval tube, oval tube film development characteristics and resistance characteristics of the outflow pipe field. Experiments use the method of control variables, the main parameters:steam pressure 8?25 kPa?the inlet flow rate of steam 15?60 m/s?Air flow rate 3?5.2 m/s? Spray density 0.03?0.12 kg/m·s?Air temperature 25??40? and Air humidity 40%?60%.Furthermore, this paper studied on horizontal oval tube falling film liquid flow numerical simulation. VOF (volume of fluid) method is used to track the gas-liquid surface. And obtained the influence laws of film flow and film thickness distribution in the situation of different tube pitch?tube diameter and spray density. In the range of tube circumferential angle from 0°to 180°, the falling film thickness decreases first and then increases. The film thickness increases with the spray density increase, decreases with the increasing of tube pitch. Compared with pipe, the film of oval tube is more uniform, the volatility reduced, the influence of the oval tube is not linear and exists a optimal ellipse ratio. Oval tube wake region percentage decreases, with more uniform circumferential wall of the film, the heat transfer efficiency is improved. |
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