Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation. Brinich, P. F. and Graham, R. W. Glenn Research Center NASA-TN-D-8464, E-9027 RTOP 505-05...

This thesis describes an experimental investigation of laminar flow heat transfer to water in straight and curved sections of a square duct, heated on one side only. Heat transfer coefficients in the entrance and fully developed regions of the straight section are presented for a range of Grashof to Reynolds number ratios. For fully developed flow, heat transfer coefficients 4.5 times greater than pure forced convection coefficients were obtained. Heat transfer coefficients in the curved section, normalized with straight section data, are given as a function of an empirical parameter, dependent on Grashof (based on centrifugal acceleration) and Reynolds numbers. (Author).

Three-dimensional Computational Fluid Dynamics (CFD) models were developed to simulate fluid flow and heat transfer in a variety of helical channel geometries: circular and elliptical. Laminar flow was observed for Reynolds number between 200 and 1000. Code validation was done for developing steady laminar flow in a circular curved channel. The CFD results were compared to previous numerical results to verify that the model was producing valid results. The curve of the channel has a centrifugal effect on the fluid flow creating secondary flow known as Dean cells. This secondary flow moves the location of the maximum axial velocity towards the outer wall of the channel and alters the developing temperature profiles as well. The helical models were designed to assess if the effect of the curve increases the rate of heat transfer when a constant surface temperature is applied to the wall of the channel. Different channel geometries were used to determine the effects on fluid flow and heat transfer in a helical channel. A channel with a 180° turn was also modeled in two different ways. One with a rounded 180° curve and the other with three perpendicular channels joined together to create a square 180° turn. The three combined channels are typically easier and less expensive to manufacture, but the fluid flow and heat transfer properties need to be considered before selecting the design. The helical models produce similar results. The Dean vortices produced in the secondary flow within the fluid aids in the heat transfer properties of the fluid. Of all the helical cases, a horizontal ellipse cross section achieved the highest outlet-inlet temperature difference, especially for higher Reynolds numbers. Even though the horizontal elliptical helix model produced the highest temperature difference, the circular helix model produced the highest percent increase over its straight model. Using a figure of merit to compare the Nusselt numbers and friction factors for each case, the circular helix geometry proved to me the best design option. The three combined channels produced better heat transfer results than the rounded channel for higher Reynolds numbers, with higher mean outlet temperatures. At lower Reynolds numbers, the results were very similar with only a 0.4% difference in results.

Engineering systems and materials do experience heating or cooling of some kind during operation. Modelling and theoretical analysis of heat transfer problems will enhance the functional success of the materials and enable new product development in engineering. The special issue on “Engineering Fluid Flows and Heat Transfer Analysis” of the journal “Diffusion Foundations” presents some novel theoretical analysis of various engineering heat transfer problems. Topics covered in this special issue include reactive fluid flow, magnetohydrodynamics, Newtonian and non-Newtonian fluid flow, natural convection, forced convection, mixed convection, porous media flow, and thermal radiation absorption effects.