本文選題：繞流 + 特征尺寸�。� 參考：《華中科技大學(xué)》2015年碩士論文

【摘要】：本文提出一種繞流管束雷諾數(shù)和特征尺寸計(jì)算的新方法,繞流管束雷諾數(shù)的特征尺寸不應(yīng)只取管外徑,還應(yīng)計(jì)入管間距、排間距和管間流速的影響。以勻速進(jìn)氣橫掠管束為背景,采用Fluent軟件和標(biāo)準(zhǔn)k-ε模型,建立8×8順排管束和8×8叉排管束二維網(wǎng)格模型進(jìn)行數(shù)值模擬。將繞流管束的流動(dòng)壓降當(dāng)量為流道的沿程壓降,分析了不同管束尺寸和不同流速下,流動(dòng)壓降的變化規(guī)律,得到繞流雷諾數(shù)及其特征尺寸隨管束結(jié)構(gòu)參數(shù)和流速的變化關(guān)系。結(jié)果表明,繞流管束雷諾數(shù)及其特征尺寸計(jì)算的新方法能更真實(shí)地反映繞流管束時(shí),結(jié)構(gòu)尺寸和流速對(duì)流道或流場(chǎng)特征尺寸de的影響。搭建了水膜蒸發(fā)空冷器實(shí)驗(yàn)臺(tái),調(diào)試了實(shí)驗(yàn)測(cè)量系統(tǒng),選取了125組工況(5個(gè)熱水溫度×5個(gè)熱水流量×5個(gè)迎面風(fēng)速)進(jìn)行實(shí)驗(yàn)。在各管程進(jìn)出口裝設(shè)熱電阻,測(cè)量各管程管內(nèi)熱水進(jìn)出口溫度,進(jìn)而算得各管程熱水的放熱量;分析了熱水溫度、熱水流量和迎面風(fēng)速對(duì)換熱量及管內(nèi)熱水溫度軸向分布的影響。各管程下方都裝設(shè)水風(fēng)逆流濕空氣參數(shù)測(cè)量系統(tǒng),利用系統(tǒng)中的水溫傳感器測(cè)量噴淋水溫,分析了噴淋水溫在豎直方向的分布。實(shí)驗(yàn)及分析表明:熱水流量增至6m3/h之前,隨熱水流量的增大,換熱量逐漸增大;但熱水流量增至6m3/h之后,再增大熱水流量,換熱量變化趨于平緩。隨熱水溫度的升高,換熱量增大。迎面風(fēng)速增至2.788m/s之前,隨迎面風(fēng)速的增大,換熱量逐漸增大;但迎面風(fēng)速增至2.788m/s之后,再增大迎面風(fēng)速,換熱量變化趨于平緩。上管程的熱水溫降幅度最大,中管程溫降幅度和下管程溫降幅度相當(dāng)。噴淋水從噴嘴噴出后,接近管束時(shí)溫度降至最低;噴淋水經(jīng)上管程和中管程吸熱,溫度升至最高;噴淋水再經(jīng)下管程和雨區(qū)到水箱,溫度逐漸降低。對(duì)本實(shí)驗(yàn)裝置,噴淋量為0.8 m3/h時(shí),換熱量保持最大的迎面風(fēng)速范圍是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.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ051.5

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