复合循环空冷技术在太阳能热电厂的应用研究

发布时间：2018-11-28 14:48

【摘要】：太阳能热发电厂一般建在缺水的华北、东北、西北等“三北”地区,而复合循环空冷技术可以解决缺水的问题,而且比直接空冷技术更加有优势。本文基于复合循环空冷(复间冷)系统的组成和传热过程,定性分析了双相变换热器(凝汽器)的管壁温度、液氨进口流速、入口温度对凝汽器换热的影响,确定了复间冷凝汽器换热的影响因素,建立了复间冷机组变工况特性下凝汽器换热器的计算模型,并以凝汽器最佳换热为目标,给出运行工况复间冷系统最佳换热面积的计算方法。以张北地区某50MW太阳能热发电复间冷系统机组参数为基准,通过分析计算,揭示了复间冷机组凝汽器最佳换热规律,所得结果可为复间冷系统设计和运行优化提供可靠理论依据。(1)对电站空冷双相变换热器换热管内氨进行汽液两相流蒸发沸腾的数值模拟,将换热器简化为研究单根水平换热管,分析了不同管壁温度、液氨进口流速、入口温度对沸腾传热性能的影响。研究表明:随着管壁温度的升高,会导致管内换热系数变小;随着液氨进口流速的增加,管内换热性能在增加,同时管内压力也在降低;随着液氨进口温度的增加,管内换热性能在下降,而压力几乎没有变化。(2)确定双相变换热器的最优管壁温度、进口流速、入口温度的组合形式。结果表明:壁面温度为302.96K、进口流速为0.1m/s、入口温度为278.15K时换热管的换热效果最佳。确定了凝汽器最优管壁温度、液氨进口流速、入口温度组合方式结合电站实际运行环境可以确定换热器的最佳换热面积。(3)本文建立了逆制冷循环空冷系统发电模型,并采用EES(Engineering Equation Solver)软件编程,对逆制冷系统模型进行模拟计算。通过系统的性能分析和热力优化研究。本文从朗肯系统的性能指标作为出发点,分别分析不可逆损失、膨胀机输出功率、系统热效率和?效率对系统的影响,选取了蒸发温度、冷凝温度、过热度、冷凝度、环境温度、膨胀机等熵效率这几个影响参数作为系统存在的自变量。对系统有利的自变量是蒸发温度、环境温度、膨胀机等熵效率,对系统不利的自变量是冷凝温度,过热度对系统性能的影响不大,过冷度对整个系统是有利的,但是受益并不是很大。(4)建立了正制冷循环空冷系统模型,运用EES进行模拟计算,计算得到蒸发温度和环境温度对系统是有利因素;冷凝温度和过热度对系统是不利因素;过冷度对系统是没有影响的。
[Abstract]:Solar thermal power plants are generally built in the "three northern" regions, such as North China, Northeast, Northwest, etc. The composite cycle air cooling technology can solve the problem of water shortage, and has more advantages than direct air cooling technology. Based on the composition and heat transfer process of the compound cycle air cooling system, the effects of the tube wall temperature, the inlet velocity of ammonia and the inlet temperature on the heat transfer of the double phase change heat exchanger (condenser) are qualitatively analyzed in this paper. The factors affecting the heat transfer of the complex intercooler condenser are determined, and the calculation model of the condenser heat exchanger under the variable working condition characteristic of the complex intercooler unit is established, and the optimum heat transfer of the condenser is taken as the goal. The calculation method of optimum heat transfer area of complex intercooling system under operating condition is given. Based on the parameters of a 50MW solar complex cooling system in Zhangbei area, the optimum heat transfer law of the condenser is revealed through analysis and calculation. The results can provide a reliable theoretical basis for the design and operation optimization of the complex intercooling system. (1) numerical simulation of vapor-liquid two-phase flow evaporation boiling of ammonia in the heat exchanger tube of air-cooled double-phase heat exchanger in power station. The heat exchanger was simplified into a single horizontal heat exchanger. The effects of different tube wall temperature, inlet flow rate of ammonia and inlet temperature on boiling heat transfer performance were analyzed. The results show that the heat transfer coefficient decreases with the increase of the temperature of the tube wall, the heat transfer performance increases with the increase of the inlet velocity of ammonia, and the pressure in the tube decreases. With the increase of the inlet temperature of liquid ammonia, the heat transfer performance of the tube is decreasing, but the pressure is almost unchanged. (2) the optimal wall temperature, inlet velocity and inlet temperature of the double phase change heat exchanger are determined. The results show that the heat transfer efficiency of the tube is the best when the wall temperature is 302.96K, the inlet velocity is 0.1m / s, and the inlet temperature is 278.15K. The optimal tube wall temperature, inlet ammonia flow rate and inlet temperature combination of condenser can be used to determine the optimal heat transfer area of the heat exchanger combined with the actual operating environment of the power station. (3) in this paper, a power generation model of the inverse refrigeration cycle air cooling system is established. The inverse refrigeration system model is simulated and calculated by using EES (Engineering Equation Solver) software. Through the system performance analysis and thermodynamic optimization research. In this paper, the irreversible loss, output power of expander, thermal efficiency and thermal efficiency of Rankine system are analyzed respectively from the point of view of Rankine system performance index. The effect of efficiency on the system is studied. The influence parameters such as evaporation temperature, condensation temperature, superheat degree, condensation degree, ambient temperature and entropy efficiency of expander are selected as independent variables of the system. The favorable independent variables to the system are evaporation temperature, ambient temperature, entropy efficiency of expander, and the unfavorable independent variable to the system is the condensation temperature. The superheat has little effect on the system performance, and the undercooling is beneficial to the whole system. But the benefit is not very great. (4) the air cooling system model of the positive refrigeration cycle is established, and the evaporation temperature and the ambient temperature are the favorable factors to the system. Condensation temperature and superheat are unfavorable factors to the system, while undercooling has no effect on the system.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621

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