封闭腔体自然对流数值模拟研究

发布时间：2018-09-07 10:12

【摘要】：自然对流在实际生活中应用的例子随处可见,认识和研究自然对流的基本特征对调节建筑室内空气温度、加强或削弱热量传递、建筑节能具有很大的指导意义。本文采用流体力学、传热学理论研究了物性参数处理方法对自然对流数值计算的影响,并运用数值研究方法对不同空间位置、水平体积力、温度分布影响下的自然对流问题展开研究。首先,采用理论和数值方法研究三维方腔自然对流换热问题,将数值计算的平均努塞尔数与基准对比,其误差均在0.85%以内,验证了模型和计算方法的正确性。将不同物性处理方法的计算结果对比得出：温差为500K时,流体密度、导热系数采用常物性计算误差高达9.54%、-4.82%,为确保计算结果准确,在大温差自然对流数值计算中,应考虑流体密度、导热系数随温度变化对计算结果的影响；流体比热容、动力粘度采用常物性计算误差相对较小,当温差等于500K时,最大误差为2.17%、0.39%,由于计算误差随温差增大而增大,当温差大于500K时也应考虑比热容、动力粘度随温度变化对计算的影响。其次,研究了水平体积力作用下封闭腔体自然对流问题,得出对流强度随水平正方向体积力增大而增大,随水平负方向体积力增加而削弱。在倾斜角影响下,封闭腔体内空气受力状态发生了改变,导致自然对流强度随负倾斜角增大而减弱,对流强度随正倾斜角增大由增大逐渐变为减弱。再次,研究了方腔高温壁面不同温度分布的空气对流情况,得出温度分布对对流强度的影响,探索定温差情况下改变边界温度分布来加强和削弱自然对流作用的方法。
[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.
【学位授予单位】：辽宁工程技术大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU831.1

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