Abstract

In this study, the numerical simulations for multiphase fluid flow inside a smooth and dimpled tube were investigated at low mass velocities during the condensation of R-134a to determine the pressure drop. The numerical analysis was conducted at a dryness fraction of 0.5, temperature of saturation of 30–50°C, and mass fluxes range between 50 and 200 kg m⁻² s⁻¹. The impact of mass flux on the pressure drops had been studied along the smooth and dimpled tube. The smooth and dimpled tubes were designed with an inside and outside diameter of 8.38 and 9.54 mm, respectively. The specifications of the dimpled tube were o = 1 mm, p = 5.08 mm, z = 4.99 mm, and e = 0.5 mm. The Volume of Fluid (VOF) flow model was utilized in this study and the flow field was assumed to be three-dimensional, transient and turbulent. With an increase in mass flux for both smooth and dimple tubes, total pressure drop and frictional pressure drop increases. The numerically simulated two-phase friction factor was compared with the well-known correlations of the dimple tube. Also, the numerically simulated pressure drop for the dimple tube was more compared with the plain tube and the pressure drop decreases with an increase in temperature of saturation.

中文翻译：

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饱和温度对 R-134a 在波纹管内冷凝过程中压降的影响：数值研究

摘要

在这项研究中，研究了在 R-134a 冷凝过程中低质量速度下光滑和带凹坑的管内多相流体流动的数值模拟，以确定压降。数值分析是在 0.5 的干度、30-50°C 的饱和温度和 50 到 200 kg m ^-2 s ^-1之间的质量通量范围内进行的。质量通量对压降的影响已经沿着光滑和带凹坑的管子进行了研究。光滑管和带波纹管的内径和外径分别设计为 8.38 和 9.54 mm。波纹管的规格为o  = 1 mm、p = 5.08 mm、z = 4.99 mm 和e= 0.5 毫米。本研究采用流体体积 (VOF) 流动模型，假定流场是三维的、瞬态的和湍流的。随着光滑管和凹坑管的质量通量增加，总压降和摩擦压降增加。将数值模拟的两相摩擦系数与凹坑管的众所周知的相关性进行了比较。此外，与普通管相比，凹坑管的数值模拟压降更多，并且压降随着饱和温度的升高而减小。