本文選題：板翅式換熱器 + 平直翅片��； 參考：《天津大學》2015年碩士論文

【摘要】：板翅式換熱器具有結構緊湊、效率高的特點,被廣泛應用在汽車、航空、空分等領域。利用經實驗驗證的CFD模型來揭示狹小翅片通道內局部流動、傳熱特性,對優(yōu)化翅片結構、開發(fā)新型翅片有實際應用價值。本文針對平直、鋸齒、波紋翅片通道內流動的特點,選擇合適的低雷諾數(shù)湍流模型并結合湍流普朗特數(shù)模型,建立了準確計算翅片性能的三維數(shù)值模型。通過以上兩個改進措施,使得平直翅片的計算j因子的平均絕對誤差從17.94%降到6.93%,提高了計算精度。同時通過計算發(fā)現(xiàn)翅片中心處與進口流體溫差較上(下)蓋板與進口流體的溫差低5-18%,忽略翅片縱向導熱或將模型簡化為二維流動會帶來誤差。針對18種不同幾何結構的平直翅片進行數(shù)值模擬,得到翅片性能關聯(lián)式,該關聯(lián)式較日本神鋼“ALEX”性能曲線有更高的精度。在驗證鋸齒形翅片數(shù)值模型正確性的基礎上,探究了雷諾數(shù)、翅片厚度、翅片節(jié)距、翅片高度等參數(shù)對流動、傳熱的影響;其中翅片厚度和翅片節(jié)距對性能影響較大。隨著翅片厚度增加,在迎風面后側會形成對稱的渦流區(qū)域,使壓降增大而對強化傳熱效果不明顯;減小翅片節(jié)距,破壞鋸齒形翅片通道內溫度邊界層和速度邊界層更頻繁,傳熱系數(shù)和壓降均增大。通過與實驗數(shù)據(jù)對比,驗證了計算波紋翅片通道性能的數(shù)值模型的正確性,并比較了在不同雷諾數(shù)下翅片通道內的流動狀態(tài)。在低雷諾數(shù)區(qū)域流體流動與平直翅片相似;隨著雷諾數(shù)增大,流體在波峰、波谷處形成渦流區(qū)域,使壁面區(qū)域流體與主體流體發(fā)生混合,強化傳熱過程。在縱向方向上,靠近上下蓋板區(qū)域存在對稱的Taylor-Gortler渦;在過渡流區(qū)域渦流較大;而在湍流區(qū)域,湍流會抑制Taylor-Gortler渦的形成,渦流變小。
[Abstract]:Plate-fin heat exchanger is widely used in automobile, aviation, air separation and other fields because of its compact structure and high efficiency. The experimental CFD model is used to reveal the local flow and heat transfer characteristics in a narrow fin channel, which has practical application value in optimizing fin structure and developing new fin. In this paper, according to the characteristics of flow in straight, sawtooth and corrugated fin channels, a three dimensional numerical model for accurate calculation of fin performance is established by selecting appropriate low Reynolds number turbulence model and combining with turbulent Plantt number model. Through the above two improvement measures, the average absolute error of calculating j factor of flat fin is reduced from 17.94% to 6.933%, and the accuracy of calculation is improved. At the same time, it is found that the temperature difference between the center of the fin and the inlet fluid is 5-18% lower than that between the upper (lower) cover plate and the inlet fluid. The error will be caused by neglecting the longitudinal heat conduction of the fin or simplifying the model to two-dimensional flow. Based on the numerical simulation of 18 kinds of straight fins with different geometric structures, the performance correlation of the fins is obtained, which has a higher accuracy than the "ALEX" performance curve of Shengang Japan. On the basis of verifying the correctness of the sawtooth fin numerical model, the effects of parameters such as Reynolds number, fin thickness, fin pitch, fin height on the flow and heat transfer are investigated, among which the fin thickness and fin pitch have great influence on the performance. With the increase of fin thickness, a symmetrical eddy current region will be formed at the back of the windward, which will increase the pressure drop without obvious effect on the enhancement of heat transfer, decrease the fin pitch and destroy the temperature boundary layer and velocity boundary layer in the sawtooth fin channel more frequently. Both heat transfer coefficient and pressure drop increase. The correctness of the numerical model for calculating the channel performance of corrugated fin is verified by comparing with the experimental data and the flow state in the fin channel under different Reynolds numbers is compared. The fluid flow in the low Reynolds number region is similar to that in the flat fin, and with the increase of the Reynolds number, the eddy current region is formed at the peak and trough of the wave, which makes the fluid mixing with the main fluid in the wall area and strengthens the heat transfer process. In the longitudinal direction, there are symmetrical Taylor-Gortler vortices near the upper and lower cover plates; in the transitional flow region, the vortices are larger; in the turbulent region, the formation of Taylor-Gortler vortices is inhibited and the eddy current becomes smaller.
【學位授予單位】：天津大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ051.5

【參考文獻】

相關期刊論文 前4條

1 文鍵;李亞梅;王斯民;厲彥忠;吳晨龍;;板翅式換熱器平直翅片表面流動及傳熱特性[J];化學工程;2012年10期

2 董軍啟;陳江平;袁慶豐;陳芝久;;板翅換熱器平直翅片的傳熱與阻力性能試驗[J];農業(yè)機械學報;2007年08期

3 董軍啟;陳江平;陳芝久;;鋸齒翅片的傳熱與阻力性能試驗[J];化工學報;2007年02期

4 祝銀海;厲彥忠;;板翅式換熱器翅片通道中流體流動與傳熱的計算流體力學模擬[J];化工學報;2006年05期

相關博士學位論文 前1條

1 董軍啟;車輛冷卻系統(tǒng)空氣側特性研究[D];上海交通大學;2008年

相關碩士學位論文 前2條

1 徐振元;工程車輛波紋翅片散熱器特性分析與應用研究[D];吉林大學;2012年

2 許偉;幾種典型翅片傳熱及阻力特性的數(shù)值研究與分析[D];清華大學;2005年

，

本文編號：1896300