Investigation of heat transfer and pressure drop of turbulent flow in tubes with successive alternating wall deformation under constant wall temperature boundary conditions

Abstract

In this study, the effects of the presence of multi-longitudinal vortex and various rotation angles between the pitches of alternating elliptical axis (AEA) tubes on heat transfer and pressure drop of turbulent flow were numerically investigated. Turbulent flow of water fluid was simulated at Reynolds numbers of 10,000-60,000. The turbulent flow and heat transfer in the tubes were discussed in terms of parameters such as static pressure, velocity magnitude, wall shear stress, turbulent intensity, performance evaluation criterion and the field synergy principle. The results demonstrate that most heat transfer occurs in the transition zone, but this also caused a high rate of pressure drop. Increasing the rotation angle between pitches from 60°to 80°increased the heat transfer, which increased the number of the multi-longitudinal vortices from four to eight and better mixed the cold fluid with the hot fluid near the tube wall on more paths. The friction factor decreased and the average Nusselt number increased as the Reynolds number increased. Both parameters increased as the angle of the pitch rotation increased. The performance evaluation criteria for all AEA tubes at a constant pumping power showed that the highest value (1.09) was achieved at a low Reynolds number (Re = 10,000) in the AEA 90°tube.

Elliptical double corrugated tubes for enhanced heat transfer

“…Performance of the double corrugated tubes was compared to the AEA tubes reported by Khaboshan and Nazif, [13]. The latter tubes were modelled in the turbulent flow regime with constant temperature of the tube wall.…”

“…The global performance of the double corrugated tubes was analysed using the most commonly adopted performance evaluation criterion PEC, which is defined by Eq. 16 [1,13].…”

“…The main research efforts over the last five years have been focused on investigating spirally or transversally corrugated tubes and channels, fins or inserts of wavy strip tapes, and other techniques that allow disturbance of thermal boundary layers [8][9][10][11][12][13][14][15][16]. A concept of fluted tubes was investigated by Srinivasan et al [12].…”

“…Li et al [18] demonstrated that AEA tubes give at least an 84% increase in heat transfer compared to a straight tube. Khaboshan and Nazif [13] performed modelling of AEA tubes for turbulent flow and showed that the tubes have an enhanced heat transfer performance at a performance evaluation criterion that is above 1 for some flow ranges. Meng et al [19] proved experimentally that the heat transfer is 100-500% enhanced in AEA tubes for the Reynolds number (Re) region from 500 to 2300 with a 100-350% increase in flow resistance.…”

Performance Assessment of Double Corrugated Tubes in a Tube-In-Shell Heat Exchanger

“…Multiple studies on different augmented and/or coated surfaces [6], e.g., tubes with fitted inserts [9][10][11][12], grooved surfaces [13][14][15] and structured microchannels [16] have been reported. Various types of corrugations have been analysed as well; for instance, tubes with multiple starts [17], tubes with alternating ellipse axes [18,19] and double corrugated tubes with constant hydraulic diameter, D h , or constant cross-section area, A c , [20,21]. All of the reported numerical and/or experimental studies have demonstrated a significant increase in heat transfer inside the tube geometry with higher or lower increase in pressure drop compared to a baseline case.…”