水膜蒸发式空冷器实验研究及管束绕流雷诺数特征尺寸研究

发布时间：2018-04-26 05:15

本文选题：绕流 + 特征尺寸　；参考：《华中科技大学》2015年硕士论文

【摘要】：本文提出一种绕流管束雷诺数和特征尺寸计算的新方法,绕流管束雷诺数的特征尺寸不应只取管外径,还应计入管间距、排间距和管间流速的影响。以匀速进气横掠管束为背景,采用Fluent软件和标准k-ε模型,建立8×8顺排管束和8×8叉排管束二维网格模型进行数值模拟。将绕流管束的流动压降当量为流道的沿程压降,分析了不同管束尺寸和不同流速下,流动压降的变化规律,得到绕流雷诺数及其特征尺寸随管束结构参数和流速的变化关系。结果表明,绕流管束雷诺数及其特征尺寸计算的新方法能更真实地反映绕流管束时,结构尺寸和流速对流道或流场特征尺寸de的影响。搭建了水膜蒸发空冷器实验台,调试了实验测量系统,选取了125组工况(5个热水温度×5个热水流量×5个迎面风速)进行实验。在各管程进出口装设热电阻,测量各管程管内热水进出口温度,进而算得各管程热水的放热量;分析了热水温度、热水流量和迎面风速对换热量及管内热水温度轴向分布的影响。各管程下方都装设水风逆流湿空气参数测量系统,利用系统中的水温传感器测量喷淋水温,分析了喷淋水温在竖直方向的分布。实验及分析表明:热水流量增至6m3/h之前,随热水流量的增大,换热量逐渐增大;但热水流量增至6m3/h之后,再增大热水流量,换热量变化趋于平缓。随热水温度的升高,换热量增大。迎面风速增至2.788m/s之前,随迎面风速的增大,换热量逐渐增大;但迎面风速增至2.788m/s之后,再增大迎面风速,换热量变化趋于平缓。上管程的热水温降幅度最大,中管程温降幅度和下管程温降幅度相当。喷淋水从喷嘴喷出后,接近管束时温度降至最低;喷淋水经上管程和中管程吸热,温度升至最高;喷淋水再经下管程和雨区到水箱,温度逐渐降低。对本实验装置,喷淋量为0.8 m3/h时,换热量保持最大的迎面风速范围是2.788m/s~3.129m/s。
[Abstract]:In this paper, a new method for calculating Reynolds number and characteristic size of tube bundles around flow is proposed. The characteristic dimensions of Reynolds numbers should not only be taken from the outer diameter of tubes, but also take into account the effects of tube spacing, row spacing and flow rate between tubes. In this paper, the 2-D grid models of 8 脳 8 and 8 脳 8 cross row tube bundles are established by using Fluent software and standard k- 蔚 model. The flow pressure drop around the tube bundle is equivalent to the pressure drop along the channel. The variation law of the flow pressure drop under different tube bundle size and different flow velocity is analyzed, and the relationship between the Reynolds number and its characteristic size along the bundle structure and velocity is obtained. The results show that the new method for calculating Reynolds number and characteristic size of the flow around the tube bundle can more truly reflect the influence of the structure size and the flow velocity on the characteristic dimension de of the flow channel or the flow field when the flow around the tube bundle is carried out. A water film evaporative air cooler was set up and the experimental measurement system was debugged. 125 working conditions (5 hot water temperature 脳 5 hot water flow rate 脳 5 face wind speed) were selected to carry out the experiment. The thermal resistance is installed at the inlet and outlet of each pipe to measure the inlet and outlet temperature of the hot water in each pipe, and the heat release of each side of the hot water is calculated, and the temperature of the hot water is analyzed. The influence of hot water flow and wind speed on heat transfer and axial distribution of hot water temperature in pipe. A system for measuring the parameters of wet air with water wind countercurrent is installed at the bottom of each pipe. The spray water temperature is measured by the water temperature sensor in the system, and the distribution of the spray water temperature in the vertical direction is analyzed. The experiment and analysis show that the heat exchange increases gradually with the increase of the hot water flow rate before increasing to 6m3/h, but when the hot water flow increases to 6m3/h, then increases the hot water flow, and the change of heat exchange tends to be gentle. The heat exchange increases with the increase of hot water temperature. The heat transfer increases gradually with the increase of the head-on wind speed before increasing to 2.788m/s, but when the head-on wind speed increases to 2.788m/s, then increases the head-on wind speed, and the change of heat transfer tends to be gentle. The temperature drop of hot water in the upper pipe is the largest, and the temperature drop in the middle pipe is the same as that in the lower pipe. After spray water was ejected from the nozzle, the temperature dropped to the lowest when it was close to the tube bundle; the temperature of the spray water rose to the highest through the upper and middle tubes, and the temperature of the spray water gradually decreased after passing through the lower pipe and the rain area to the water tank. For this device, the maximum head-on wind speed of the heat exchange is 2.788 m / s / s 3.129 m / s when the spray volume is 0.8 m3 / h.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.5

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