本文關(guān)鍵詞：異型釘頭管強(qiáng)化傳熱及流動特性研究　出處：《青島科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 異型釘頭管 強(qiáng)化傳熱 流動特性 數(shù)值模擬 場協(xié)同 萘升華實驗

【摘要】：隨著社會的快速發(fā)展,能源的節(jié)約和合理利用已經(jīng)成為當(dāng)今世界各國可持續(xù)發(fā)展的主題。強(qiáng)化傳熱能提高換熱設(shè)備的效率,有效緩解能源短缺問題,一直是國內(nèi)外節(jié)能減排發(fā)展關(guān)注的重點問題。釘頭管作為一種高效的強(qiáng)化傳熱元件,具有擴(kuò)展表面、增加流體湍流程度的作用,廣泛應(yīng)用于石油化工、煤化工、冶金、陶瓷、建材等領(lǐng)域中。異型釘頭雖然已被工業(yè)界所采用,但研究主要致力于釘頭形狀和釘頭尺寸、排列方式等,且研究參數(shù)、應(yīng)用領(lǐng)域等各不相同,沒有進(jìn)行最優(yōu)化分析,特別是異型釘頭管應(yīng)用于傳熱系數(shù)較低的氣體側(cè)的強(qiáng)化傳熱及流動特性,缺乏系統(tǒng)詳細(xì)的研究數(shù)據(jù),仍無法說明哪種釘頭形狀具有最好的綜合性能,且對其強(qiáng)化傳熱機(jī)理還缺乏統(tǒng)一的認(rèn)識。本文采用“理論分析—數(shù)值模擬—實驗驗證”相結(jié)合的研究方法,對圓形、橢圓形、滴形三種不同形狀異型釘頭管的傳熱及流動特性進(jìn)行了研究。從理論方面對釘頭管的傳熱及流動特性進(jìn)行分析,為數(shù)值模擬和實驗等提供指導(dǎo)依據(jù)。以釘頭管為研究對象,在風(fēng)洞背景下,以分析釘頭管外側(cè)流體流動狀態(tài)和換熱機(jī)理為研究目的,利用當(dāng)前發(fā)展比較成熟的CFD數(shù)值模擬技術(shù)和萘升華實驗進(jìn)行了研究。利用正交試驗設(shè)計法針對圓形釘頭設(shè)計9種釘頭管的計算模型,并對其進(jìn)行數(shù)值模擬,獲得釘頭管外空氣側(cè)的壓力場、溫度場和速度場的分布,分析釘頭管的流動與傳熱性能。對正交試驗結(jié)果進(jìn)行分析,得出在以后對釘頭管流動和傳熱性能的研究中,工作重點主要應(yīng)放在每環(huán)釘頭個數(shù)和釘頭高度的優(yōu)化上的結(jié)論。對圓形釘頭管進(jìn)行數(shù)值模擬,結(jié)果表明在模擬的雷諾數(shù)范圍內(nèi),釘頭管的壓降約為光管的1.35-2.31倍,釘頭管的總表面換熱系數(shù)約為光管的1.10-1.72倍。釘頭管的綜合性能均優(yōu)于光管。當(dāng)釘頭高度為45mm,每環(huán)釘頭個數(shù)為8,縱向間距為30mm,釘頭半徑為5mm時,釘頭管的綜合換熱性能約為釘頭高度為25mm,每環(huán)釘頭個數(shù)為4,縱向間距為30mm,釘頭半徑為4mm時的1.15-1.29倍。對三種不同截面形狀的釘頭管進(jìn)行數(shù)值模擬,通過對單位質(zhì)量換熱量、單位面積換熱量、總表面換熱系數(shù)、阻力性能、綜合性能的模擬結(jié)果比較,得到滴形釘頭管的傳熱和流動特性都是三者之中最佳,說明采用滴形釘頭管,可以收到強(qiáng)化傳熱和降低流阻的雙重效果。對滴形釘頭管釘頭高度、每環(huán)釘頭個數(shù)、基管高度、釘頭環(huán)數(shù)、管內(nèi)壁溫與入口溫差以及入口空氣速度等進(jìn)行數(shù)值研究,并研究了釘頭管空氣側(cè)流場的協(xié)同性。對釘頭高度和每環(huán)釘頭個數(shù)的研究表明,在每環(huán)釘頭個數(shù)固定、釘頭高度變化時,釘頭管的單位面積換熱量、總表面換熱系數(shù)、阻力、綜合性能大多在釘頭高度為35mm時出現(xiàn)高峰值。對基管高度的研究表明,單位面積換熱量、總表面換熱系數(shù)、阻力性能、綜合性能大多隨著基管高度的增加而先減小后增大。對釘頭環(huán)數(shù)的研究表明,單位質(zhì)量換熱量、總表面換熱系數(shù)、阻力性能、綜合性能都隨著釘頭環(huán)數(shù)的增加而增大,其增大的速率幾乎是線性的。而單位面積換熱量隨釘頭環(huán)數(shù)的增加而減小。對管內(nèi)壁溫與入口溫差的研究表明,單位質(zhì)量換熱量、單位面積換熱量、總表面換熱系數(shù)、綜合性能都隨著管內(nèi)壁溫與入口空氣溫差的增加而增大,而阻力性能隨著管內(nèi)壁溫與入口空氣溫差的增加沒有變化。對入口空氣速度的研究表明,單位質(zhì)量換熱量、單位面積換熱量、總表面換熱系數(shù)、綜合性能都隨著入口空氣速度的增大而增大,而阻力性能隨著入口空氣速度的增大逐漸減小,動量損失率越來越小。流場協(xié)同性分析表明,滴形釘頭管空氣側(cè)流場的協(xié)同優(yōu)勢非常明顯。采用萘升華技術(shù)在吸入式風(fēng)洞中對圓形、橢圓形和滴形三種不同截面形狀的釘頭管進(jìn)行實驗研究,探討釘頭縱向間距、每環(huán)釘頭個數(shù)、周向角等對換熱和流動特性的影響。結(jié)果表明:在雷諾數(shù)為0.5×105-4.1×105的范圍內(nèi),(1)釘頭表面和基管表面均在周向角Φ=90°時換熱效果最好。(2)三種釘頭管的換熱系數(shù)均隨著雷諾數(shù)的增大而增加,且均優(yōu)于光管。(3)釘頭形狀對阻力性能影響較大,滴形釘頭接近流線形,阻力較小。(4)綜合考慮換熱系數(shù)和阻力性能,滴形釘頭管的綜合換熱性能指數(shù)最高。本文對異型釘頭管的傳熱及流動特性的研究,對于指導(dǎo)釘頭管的設(shè)計和生產(chǎn)實踐都具有重要的意義。
[Abstract]:With the rapid development of society, energy conservation and rational utilization have become the theme of the sustainable development of all countries in the world. The enhancement of heat transfer can improve the efficiency of heat exchange equipment and effectively alleviate the problem of energy shortage. It has always been the focus of attention on the development of energy conservation and emission reduction at home and abroad. As an efficient heat transfer enhancement element, nail head pipe has the function of expanding the surface and increasing the degree of fluid turbulence. It is widely used in petrochemical, coal chemical industry, metallurgy, ceramics, building materials and other fields. Although the nail head shaped has been adopted by the industry, but the study focuses on the nail head shape and head size, arrangement, and Study on the parameter and application fields are not the same, not the optimization analysis, especially the enhancement of heat transfer and flow characteristics of gas special-shaped pin tube used in low heat transfer coefficient of the side the lack of detailed data system, still can not explain which nail head shape has the best overall performance, and the heat transfer enhancement mechanism is lack of unified understanding. In this paper, the heat transfer and flow characteristics of three different shapes of the nail head tube with circular shape, ellipse and drop shape are studied by means of theoretical analysis numerical simulation experimental verification. The heat transfer and flow characteristics of the nailed head tube are analyzed in theory, which provides guidance for numerical simulation and experiment. Taking the stud tube as the research object, in the context of wind tunnel, we analyzed the fluid flow and heat transfer mechanism outside the nail head pipe, and studied the CFD technology and naphthalene sublimation experiment. The calculation models of 9 kinds of nail head pipes are designed by orthogonal experimental design, and numerical simulation is carried out to obtain the distribution of pressure field, temperature field and velocity field on the air side outside the nail head pipe, and the flow and heat transfer performance of the nail head pipe are analyzed. After analyzing the results of orthogonal test, it is concluded that after the study of the flow and heat transfer performance of the nail head pipe, the key point should be put on the optimization of the number of nail head and the height of the nail head. The numerical simulation of the circular nail head tube shows that the pressure drop of the nail head pipe is about 1.35-2.31 times of the light tube in the simulated Reynolds number range, and the total surface heat transfer coefficient of the nail head tube is about 1.10-1.72 times of that of the light tube. The overall performance of the nailed head tube is better than that of the light tube. When the nail head height is 45mm, the number of nails per ring is 8, the longitudinal spacing is 30mm, and the nail head radius is 5mm. The comprehensive heat transfer performance of the nail head pipe is about 25mm, the number of nail heads per ring is 4, the longitudinal spacing is 30mm, and the nail head radius is 1.15-1.29 times of 4mm. Numerical simulation of nail head tube of three different section shapes, through the simulation results of heat transfer per unit mass per unit area, heat transfer, surface heat transfer coefficient, resistance performance and comprehensive performance comparison, get the heat transfer and flow characteristics of pin finned drop shaped tube are among the three best, the drop of nail head tube, heat transfer enhancement can receive and reduce the flow resistance of the double effect. Drop nail nail head head tube height, each ring head number, tube height, nail head ring number, tube wall temperature and the entrance temperature and air speed entrance numerical study and research the synergy of pin tube air side flow. The research on nail head height and number of nails per ring shows that when the number of nail head is fixed and the height of nail head varies, the heat transfer per unit area, the total surface heat transfer coefficient, the resistance and the comprehensive performance of the nail head pipe mostly reach a high peak value when the nail head height is 35mm. The study of the height of the tube shows that the heat transfer per unit area, the total surface heat transfer coefficient, the resistance performance and the comprehensive performance first decrease and then increase with the increase of the base height. The research on the number of nail head shows that the heat transfer per unit mass, the total surface heat transfer coefficient, the resistance performance and the comprehensive performance increase with the increase of the number of the nail head ring, and the rate of increase is almost linear. The heat transfer per unit area decreases with the increase of the number of head rings. Study on the inner wall of the tube temperature and the entrance temperature, the unit of heat, mass per unit area for heat transfer, the total surface heat transfer coefficient, comprehensive performance increases with the increase of tube wall temperature and the entrance of air temperature, and resistance with increasing tube wall temperature and the entrance of air temperature did not change. Study on the entrance of air speed show that the unit of heat, heat transfer mass per unit area and total surface heat transfer coefficient, comprehensive performance increase with the entrance of air velocity, and the resistance increases with the entrance of air velocity decreases and the momentum loss rate is more and more small. Field coordination analysis showed that the synergy of air side flow pin finned drop shaped tube is very obvious. Naphthalene sublimation technology is used to study the effects of the longitudinal distance, the number and the circumferential angle of each pin on the heat transfer and flow characteristics of the three kinds of pin shaped tubes with circular cross-section, ellipse and drop shape in the suction wind tunnel. The results show that in the range of Reynolds number of 0.5 * 105-4.1 * 105, (1) the surface of the nail head and the surface of the base tube are at the circumferential angle of =90 degrees. (2) the heat transfer coefficient of the three kinds of nailed tubes increased with the increase of Reynolds number, and all were better than those of the light tubes. (3) the nail head shape has great influence on the resistance performance, nail head drop close to streamline, small resistance. (4) considering the heat transfer coefficient and resistance performance of pin finned drop shaped tube the comprehensive heat transfer performance index is the highest. The study on the heat transfer and flow characteristics of the special-shaped nail head tube is of great significance for guiding the design and production practice of the nail head tube.
【學(xué)位授予單位】：青島科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TK172

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