封閉腔體自然對流數(shù)值模擬研究
發(fā)布時間：2018-09-07 10:12
【摘要】：自然對流在實際生活中應用的例子隨處可見,認識和研究自然對流的基本特征對調(diào)節(jié)建筑室內(nèi)空氣溫度、加強或削弱熱量傳遞、建筑節(jié)能具有很大的指導意義。本文采用流體力學、傳熱學理論研究了物性參數(shù)處理方法對自然對流數(shù)值計算的影響,并運用數(shù)值研究方法對不同空間位置、水平體積力、溫度分布影響下的自然對流問題展開研究。首先,采用理論和數(shù)值方法研究三維方腔自然對流換熱問題,將數(shù)值計算的平均努塞爾數(shù)與基準對比,其誤差均在0.85%以內(nèi),驗證了模型和計算方法的正確性。將不同物性處理方法的計算結(jié)果對比得出：溫差為500K時,流體密度、導熱系數(shù)采用常物性計算誤差高達9.54%、-4.82%,為確保計算結(jié)果準確,在大溫差自然對流數(shù)值計算中,應考慮流體密度、導熱系數(shù)隨溫度變化對計算結(jié)果的影響；流體比熱容、動力粘度采用常物性計算誤差相對較小,當溫差等于500K時,最大誤差為2.17%、0.39%,由于計算誤差隨溫差增大而增大,當溫差大于500K時也應考慮比熱容、動力粘度隨溫度變化對計算的影響。其次,研究了水平體積力作用下封閉腔體自然對流問題,得出對流強度隨水平正方向體積力增大而增大,隨水平負方向體積力增加而削弱。在傾斜角影響下,封閉腔體內(nèi)空氣受力狀態(tài)發(fā)生了改變,導致自然對流強度隨負傾斜角增大而減弱,對流強度隨正傾斜角增大由增大逐漸變?yōu)闇p弱。再次,研究了方腔高溫壁面不同溫度分布的空氣對流情況,得出溫度分布對對流強度的影響,探索定溫差情況下改變邊界溫度分布來加強和削弱自然對流作用的方法。
[Abstract]:Examples of application of natural convection in real life can be seen everywhere. Understanding and studying the basic characteristics of natural convection is of great significance in regulating indoor air temperature, strengthening or weakening heat transfer, and building energy conservation. In this paper, the effect of physical parameters on the numerical calculation of natural convection is studied by using the theory of fluid dynamics and heat transfer. The natural convection problem under the influence of temperature distribution is studied. Firstly, the theoretical and numerical methods are used to study the natural convection heat transfer problem in a three-dimensional square cavity. The errors of the average Nussel number calculated by the numerical method are within 0.85%, which verifies the correctness of the model and the calculation method. By comparing the calculation results of different physical properties treatment methods, it is concluded that when the temperature difference is 500K, the calculation error of fluid density and thermal conductivity is as high as 9.54 ~ 4.82 by using constant physical properties. In order to ensure the accuracy of the calculation results, in the numerical calculation of natural convection with large temperature difference, The effect of the variation of heat conductivity with temperature on the calculation results should be taken into account. The calculation error of constant physical property is relatively small when the specific heat capacity and dynamic viscosity of the fluid are calculated, when the temperature difference is equal to 500K, The maximum error is 2.17 / 0.39. Because the calculation error increases with the increase of temperature difference, the specific heat capacity should also be considered when the temperature difference is greater than 500K, and the influence of dynamic viscosity with temperature on the calculation should also be considered. Secondly, the natural convection problem of closed cavity under the action of horizontal volume force is studied. It is concluded that the convection intensity increases with the increase of horizontal positive volume force and weakens with the increase of horizontal negative volume force. Under the influence of incline angle, the forced state of air in the closed chamber is changed, which leads to the decrease of natural convection intensity with the increase of negative inclination angle, and the gradual change of convection intensity from the increase of positive inclination angle to the weakening of convection intensity with the increase of positive inclination angle. Thirdly, the air convection with different temperature distribution on the wall of square cavity is studied, the influence of temperature distribution on convection intensity is obtained, and the method to strengthen and weaken the natural convection by changing the boundary temperature distribution under the condition of constant temperature difference is explored.
【學位授予單位】：遼寧工程技術(shù)大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU831.1
[Abstract]:Examples of application of natural convection in real life can be seen everywhere. Understanding and studying the basic characteristics of natural convection is of great significance in regulating indoor air temperature, strengthening or weakening heat transfer, and building energy conservation. In this paper, the effect of physical parameters on the numerical calculation of natural convection is studied by using the theory of fluid dynamics and heat transfer. The natural convection problem under the influence of temperature distribution is studied. Firstly, the theoretical and numerical methods are used to study the natural convection heat transfer problem in a three-dimensional square cavity. The errors of the average Nussel number calculated by the numerical method are within 0.85%, which verifies the correctness of the model and the calculation method. By comparing the calculation results of different physical properties treatment methods, it is concluded that when the temperature difference is 500K, the calculation error of fluid density and thermal conductivity is as high as 9.54 ~ 4.82 by using constant physical properties. In order to ensure the accuracy of the calculation results, in the numerical calculation of natural convection with large temperature difference, The effect of the variation of heat conductivity with temperature on the calculation results should be taken into account. The calculation error of constant physical property is relatively small when the specific heat capacity and dynamic viscosity of the fluid are calculated, when the temperature difference is equal to 500K, The maximum error is 2.17 / 0.39. Because the calculation error increases with the increase of temperature difference, the specific heat capacity should also be considered when the temperature difference is greater than 500K, and the influence of dynamic viscosity with temperature on the calculation should also be considered. Secondly, the natural convection problem of closed cavity under the action of horizontal volume force is studied. It is concluded that the convection intensity increases with the increase of horizontal positive volume force and weakens with the increase of horizontal negative volume force. Under the influence of incline angle, the forced state of air in the closed chamber is changed, which leads to the decrease of natural convection intensity with the increase of negative inclination angle, and the gradual change of convection intensity from the increase of positive inclination angle to the weakening of convection intensity with the increase of positive inclination angle. Thirdly, the air convection with different temperature distribution on the wall of square cavity is studied, the influence of temperature distribution on convection intensity is obtained, and the method to strengthen and weaken the natural convection by changing the boundary temperature distribution under the condition of constant temperature difference is explored.
【學位授予單位】：遼寧工程技術(shù)大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU831.1
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