An Experimental and Numerical Investigation of Turbulent Variable Fluid Property Heat Transfer and Fluid Flow in Enhanced Tubes

提出的研究将从实验和数值两方面研究有较大变流体性质影响的内翅片管内的湍流换热和压降。内翅片管的几何形状是测试建模能力的理想选择，因为它们与工业相关，具有很大的表面积，由于几何形状而具有复杂的流体动力学，适合于数值建模，并且可以在实验室中在广泛的几何和操作条件下进行实验测试。10个内翅片管可用于试验研究；这些管涵盖了广泛的几何参数。该管将在加热和冷却两种情况下进行测试，测试范围是壁与体的温差。工作流体将是水、乙二醇和矿物油。在数值模拟中，主要的重点将放在发展适当的近壁模拟和适应可变流体性质上。一个新建立的各向异性湍流模型，称为涡量通量模型，将扩展用于本项目，并适用于各向异性湍流重要的轴向和螺旋翅片管。数值模型将通过与文献中详细的局部和整体数据以及本次调查的新整体数据进行比较来验证。经过验证的模型将充分描述这种几何形状的传热和压降的控制机制（特别是翅片几何形状和螺旋角的影响）。它还将提供关于在数值模型中结合可变流体性质和增强传热技术的指导，并为发展基于物理的努塞尔数和摩擦因子的相关性提出适当的方法。

The proposed research will investigate both experimentally and numerically turbulent heat transfer and pressure drop in internally-finned tubes when there are large variable fluid property effects. The internally-finned tube geometry is ideal to test modeling capabilities because they are industrially relevant, have much surface area, have complex hydrodynamics due to the geometry, are amenable to numerical modeling, and are experimentally testable in a lab over a wide range of geometric and operating conditions. Ten internally-finned tubes are available for testing the experimental investigation; these tubes cover a wide range of geometric parameters. The tube will be tested in both heating and cooling over a range of wall-to-bulk temperature differences. The working fluids will be water, ethylene glycol, and mineral oil. In the numerical modeling, primary emphasis will be placed on development of appropriate near-wall modeling and accommodation of variable fluid properties. A newly developed anisotropic turbulence model, called the vorticity flux model, will be extended for use in this project and applied to both axially and spirally finned tubes where anisotropic turbulence is important. The numerical model will be validated by comparison against detailed local and overall data from the literature, and new overall data from this investigation. The validated model will fully describe the governing mechanisms for heat transfer and pressure drop in this geometry (particularly the effects of fin geometry and helix angle). It also will provide guidance on the incorporation of variable fluid properties in numerical models and with enhanced heat transfer techniques and suggest appropriate methods for the development of physically-based correlations for Nusselt numbers and friction factors.