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

这项研究将从实验和数值两方面研究流体性质变化较大时内翅片管内的湍流换热和压降。内翅片管几何形状非常适合测试建模能力，因为它们与工业相关，具有很大的表面积，由于其几何形状而具有复杂的流体力学，易于进行数值建模，并且可以在实验室中在各种几何和操作条件下进行实验测试。有10个内翅片管可用于测试实验研究；这些管涵盖了广泛的几何参数。管子将在加热和冷却两种情况下进行测试，测试范围为壁面与主体之间的温差。工作液将是水、乙二醇和矿物油。在数值模拟中，主要的重点将是发展适当的近壁模拟和适应各种流体性质。一种新开发的各向异性湍流模型，称为涡量通量模型，将被扩展用于本项目，并应用于轴向和螺旋翅片管，其中各向异性湍流是重要的。数值模型将通过与文献中详细的局部和总体数据以及本次调查的新总体数据进行比较来验证。经过验证的模型将完全描述这种几何形状下的换热和压降调节机制(特别是翅片几何形状和螺旋角的影响)。它还将为将各种流体性质纳入数值模型和增强的传热技术提供指导，并为开发基于物理的努塞尔数和摩擦因数关联提出适当的方法。

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.