凝结换热的管束排列数值优化研究
发布时间：2018-10-12 08:45
【摘要】：电厂冷凝器作为汽轮机机组的重要辅机之一,制约着整个热力发电厂的安全经济运行。如果凝汽器的管束布置不合适就会造成其换热效率不高,进而影响整个机组的经济性能。管束排列形式的优劣对换热器运行时各项热力性能指标的好坏有重要的影响。此外决定换热器性能好坏的参数也较多,仅凭单一参数不能决定换热器是否为最佳。因此本文提出无量纲综合性能系数K,且用K曲线的斜率作为换热器换热性能的评价指标。并利用该指标对案例进行了分析。本文应用FLUENT软件,模拟水蒸气在水平管束外遇冷凝结的流动情况。数值模型基于多相流混合物模型,模型中加入自定义函数以实现蒸汽向水的转换,利用有限体积法及SIMPLE算法求解控制方程组。本文数值计算了水蒸气在由圆管、椭圆管和滴形管三种管型所组成的换热器里的换热情况,得到了在不同管型、不同排列方式及不同管间距下的水蒸气压力场、速度场、温度场和换热器传热系数的变化值。结果表明,三种管型构成的换热器当进口蒸汽流速、温度以及压力一定的情况下,滴形管凝结换热效果最好,椭圆管次之,圆管最差。三种管型叉排布置时换热效果均要优于顺排布置,其中顺排布置时,换热效果最差的为倒数第二排管;叉排布置时,最差的为倒数第二、三排管。三种管型顺排布置时,水蒸气进出口压力损失都随管束横向间距的变大而变小,随纵向间距的变大而无太大变化;叉排布置时,水蒸气进出口压力损失都随管束横向间距的变大而变小,随纵向间距的变大同样变小。三种管型换热器传热系数,顺排布置时主要取决于管束横向间距的大小,叉排布置则主要取决于管束的纵向间距。三种管型在最优布置情况下,水蒸气通过椭圆管换热器进出口压损是圆管的0.62~0.64倍;不考虑压损时,温差相差不大;在相同压损下,流速是圆管的1.5倍;传热系数是圆管的1.93~2.04倍。水蒸气通过滴形管换热器压损是圆管的0.67~0.70倍;温差比圆管大1.5℃;在相同压损下,流速是圆管的1.38~1.41倍;传热系数是圆管的1.84~1.91倍。该研究能为冷凝换热器管束排列优化设计提供可靠的参考。
[Abstract]:As one of the important auxiliary units of steam turbine, condenser in power plant restricts the safe and economical operation of the whole thermal power plant. If the tube bundle arrangement of the condenser is not suitable, the heat transfer efficiency will not be high and the economic performance of the whole unit will be affected. The arrangement of tube bundles has an important influence on the performance of heat exchangers. In addition, there are many parameters that determine the performance of the heat exchanger, and it is not possible to determine whether the heat exchanger is the best by a single parameter. Therefore, the dimensionless comprehensive performance coefficient K is proposed and the slope of K curve is used as the evaluation index of heat transfer performance of heat exchanger. This index is used to analyze the case. In this paper, FLUENT software is used to simulate the flow of water vapor in cold condensation outside the horizontal tube bundle. The numerical model is based on the mixture model of multiphase flow. The self-defined function is added to the model to realize the conversion of steam to water. The finite volume method and SIMPLE algorithm are used to solve the equations of control. In this paper, the heat transfer of water vapor in the heat exchanger composed of circular tube, elliptical tube and droplet tube is numerically calculated, and the pressure field and velocity field of water vapor are obtained under different tube types, different arrangement modes and different tube spacing. The variation of temperature field and heat transfer coefficient of heat exchanger. The results show that when the inlet steam velocity, temperature and pressure are constant, the condensation heat transfer efficiency of the droplet tube is the best, the elliptical tube is the second, and the circular tube is the worst. The heat transfer effect of the three kinds of pipe-type fork row arrangement is better than that of the forward arrangement, in which the worst heat transfer effect is the reciprocal second row, and the worst is the reciprocal second and third row. The pressure loss of water vapor inlet and outlet becomes smaller with the increase of the transverse spacing of the tube bundles, and does not change with the increase of the longitudinal spacing when the three types of pipes are arranged in a row, and the pressure loss of the inlet and outlet of the water vapor decreases with the increase of the transverse spacing of the pipe bundles. The pressure loss at the inlet and outlet of water vapor decreases with the increase of the transverse spacing of the bundle and the same with the increase of the longitudinal spacing. The heat transfer coefficient of three kinds of tube heat exchangers mainly depends on the horizontal spacing of the tube bundles and the vertical spacing of the tube bundles in the arrangement of the three kinds of tube heat exchangers. Under the optimal arrangement, the pressure loss of water vapor through the inlet and outlet of elliptical tube heat exchanger is 0.64 times of that of circular tube, the temperature difference is not different when the pressure loss is not taken into account, the velocity of flow is 1.5 times that of circular tube under the same pressure loss, and the heat transfer coefficient is 1.93 ~ 2.04 times of that of circular tube. The pressure loss of water vapor through a drop tube heat exchanger is 0.67 ~ 0.70 times of that of a circular tube, the temperature difference is 1.5 鈩，
本文编号：2265504
[Abstract]:As one of the important auxiliary units of steam turbine, condenser in power plant restricts the safe and economical operation of the whole thermal power plant. If the tube bundle arrangement of the condenser is not suitable, the heat transfer efficiency will not be high and the economic performance of the whole unit will be affected. The arrangement of tube bundles has an important influence on the performance of heat exchangers. In addition, there are many parameters that determine the performance of the heat exchanger, and it is not possible to determine whether the heat exchanger is the best by a single parameter. Therefore, the dimensionless comprehensive performance coefficient K is proposed and the slope of K curve is used as the evaluation index of heat transfer performance of heat exchanger. This index is used to analyze the case. In this paper, FLUENT software is used to simulate the flow of water vapor in cold condensation outside the horizontal tube bundle. The numerical model is based on the mixture model of multiphase flow. The self-defined function is added to the model to realize the conversion of steam to water. The finite volume method and SIMPLE algorithm are used to solve the equations of control. In this paper, the heat transfer of water vapor in the heat exchanger composed of circular tube, elliptical tube and droplet tube is numerically calculated, and the pressure field and velocity field of water vapor are obtained under different tube types, different arrangement modes and different tube spacing. The variation of temperature field and heat transfer coefficient of heat exchanger. The results show that when the inlet steam velocity, temperature and pressure are constant, the condensation heat transfer efficiency of the droplet tube is the best, the elliptical tube is the second, and the circular tube is the worst. The heat transfer effect of the three kinds of pipe-type fork row arrangement is better than that of the forward arrangement, in which the worst heat transfer effect is the reciprocal second row, and the worst is the reciprocal second and third row. The pressure loss of water vapor inlet and outlet becomes smaller with the increase of the transverse spacing of the tube bundles, and does not change with the increase of the longitudinal spacing when the three types of pipes are arranged in a row, and the pressure loss of the inlet and outlet of the water vapor decreases with the increase of the transverse spacing of the pipe bundles. The pressure loss at the inlet and outlet of water vapor decreases with the increase of the transverse spacing of the bundle and the same with the increase of the longitudinal spacing. The heat transfer coefficient of three kinds of tube heat exchangers mainly depends on the horizontal spacing of the tube bundles and the vertical spacing of the tube bundles in the arrangement of the three kinds of tube heat exchangers. Under the optimal arrangement, the pressure loss of water vapor through the inlet and outlet of elliptical tube heat exchanger is 0.64 times of that of circular tube, the temperature difference is not different when the pressure loss is not taken into account, the velocity of flow is 1.5 times that of circular tube under the same pressure loss, and the heat transfer coefficient is 1.93 ~ 2.04 times of that of circular tube. The pressure loss of water vapor through a drop tube heat exchanger is 0.67 ~ 0.70 times of that of a circular tube, the temperature difference is 1.5 鈩，
本文编号：2265504
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