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The effects of wall curvature and adverse pressure gradient on air ducts in HVAC systems using turbulent entropy generation analysis
International Journal of Refrigeration ( IF 3.5 ) Pub Date : 2020-01-16 , DOI: 10.1016/j.ijrefrig.2020.01.014
Abbas Taheri , Abdolamir Bak Khoshnevis , Esmail Lakzian

In the present study, entropy generation analysis of turbulent boundary layer was carried out to examine the effects of the wall curvature and adverse pressure gradient (APG) on air distribution ducts in HVAC systems considering both individual and simultaneous effects of these parameters and using the empirical data. Six walls, including straight wall (A), convex curved wall (B1), concave curved wall (B2), straight wall with APG (D), convex curved wall with APG (C1), and concave curved wall with APG (C2) were investigated. The air distribution ducts can be divided into various geometries, including straight duct (A*), curved duct (B*), straight diffuser (D*), and curved diffuser (C*). Furthermore, for walls with APG (D, C1, and C2), the divergence angle was chosen in such a way that no flow separation occurred in the range under consideration. The findings showed that the entropy generation resulted from turbulence dissipation was highly important in the regions near the boundary layer edge, so that the ratio of the entropy generation rate due to the turbulence dissipation to the total entropy generation rate in the regions near the boundary layer edge approximates 0.9. In fact, in these regions, a large portion of the total entropy generation rate was related to turbulence dissipation. Consequently, the turbulence dissipation in these regions was too large to be ignored. Thus, in order to achieve a more precise criterion of the dissipation of air distribution ducts in HVAC systems, the turbulence dissipation should be taken into account.



中文翻译:

壁面曲率和逆压梯度对HVAC系统中风管的影响

在本研究中,进行了湍流边界层的熵生成分析,以考察壁曲率和逆压梯度(APG)对HVAC系统中空气分配管道的影响,同时考虑了这些参数的单独影响和同时影响,并使用经验数据。六个壁,包括直壁(A),凸弯曲壁(B1),凹弯曲壁(B2),带APG的直壁(D),带APG的凸弯曲壁(C1)和带APG的凹弯曲壁(C2)被调查了。空气分配管道可分为各种几何形状,包括直管道(A *),弯管道(B *),直扩散器(D *)和弯曲扩散器(C *)。此外,对于具有APG(D,C1和C2)的墙,选择发散角时应注意在所考虑的范围内不会发生流动分离。研究结果表明,湍流耗散产生的熵在边界层边缘附近区域非常重要,因此,湍流耗散引起的熵产生速率与边界层附近区域总熵产生速率之比边缘近似0.9。实际上,在这些区域中,总熵产生率的很大一部分与湍流耗散有关。因此,这些区域的湍流耗散太大而不能忽略。因此,为了在暖通空调系统中获得更精确的空气分配管道消散标准,应考虑湍流消散。因此,在边界层边缘附近的区域中,由湍流耗散引起的熵产生率与总熵产生率之比约为0.9。实际上,在这些区域中,总熵产生率的很大一部分与湍流耗散有关。因此,这些区域的湍流耗散太大而不能忽略。因此,为了在暖通空调系统中获得更精确的空气分配管道消散标准,应考虑湍流消散。因此,在边界层边缘附近的区域中,由湍流耗散引起的熵产生率与总熵产生率之比约为0.9。实际上,在这些区域中,总熵产生率的很大一部分与湍流耗散有关。因此,这些区域的湍流耗散太大而不能忽略。因此,为了获得更精确的HVAC系统中空气分配管道消散的标准,应考虑湍流消散。因此,这些区域的湍流耗散太大而不能忽略。因此,为了在暖通空调系统中获得更精确的空气分配管道消散标准,应考虑湍流消散。因此,这些区域的湍流耗散太大而不能忽略。因此,为了在暖通空调系统中获得更精确的空气分配管道消散标准,应考虑湍流消散。

更新日期:2020-03-04
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