Abstract
A numerical study was performed to investigate the thermal performance characteristics of an enhanced tube heat exchanger fitted with punched delta-winglet vortex generators. Computational fluid dynamics modeling was applied using the k–ε renormalized group turbulence model. Benchmarking was performed using the results of the experimental study for a similar geometry. Attack angles of 30°, 50°, and 70° were used to investigate the heat transfer and pressure drop characteristics of the enhanced tube. Flow conditions were considered in the turbulent region in the Reynolds number range of 9100 to 17,400. A smooth tube was employed for evaluating the increment in the Nusselt number and the friction factor characteristics of the enhanced tube. The results show that the Nusselt number, friction factor, and thermal performance factor have a similar tendency. The presence of this insert offers a higher thermal performance factor as compared to that obtained with a plain tube. Vortex development in the flow structure aids in generating a vortex flow, which increases convective heat transfer. In addition, as the angle is varied, it is observed that the largest attack angle provides the highest thermal performance factor. The greatest increase in the Nusselt number and friction factor, respectively, was found to be approximately 3.7 and 10 times greater than those of a smooth tube. Through numerical simulations with the present simulation condition, it is revealed that the thermal performance factor approaches the value of 1.1. Moreover, the numerical and experimental values agree well although they tend to be different at high Reynolds number conditions. The numerical and experimental values both show similar trends in the Nusselt number, friction factor, and thermal performance factor.
Highlights
The high performance requirements of heat exchange devices have resulted in the development of high performance heat exchangers
After publishing Ref. [22], we were motivated to extend the work to a numerical study of higher Reynolds numbers inside the tube in order to address the limitation of the experimental apparatus at higher mass flow rates
The Nusselt number was compared by using the Petukhov and Gnielinski equations [24], while the friction factor was evaluated using the Blasius equation [25]
Summary
The high performance requirements of heat exchange devices have resulted in the development of high performance heat exchangers. The passive heat transfer enhancement methods that are still used by the majority of researchers are swirl devices in the form of twisted tape [3,4,5], wire coil [6,7], helical screw [8,9], and vortex generators in the form of a winglet [10,11,12] These were investigated under various parameters to determine the important factors that affect the performance of the heat exchanger. [22], we were motivated to extend the work to a numerical study of higher Reynolds numbers inside the tube in order to address the limitation of the experimental apparatus at higher mass flow rates This is a reason why the present work has research novelty when compared to the previously published study. We verify the obtained results by comparing them with those of our previous experimental study [22] before comprehensively analyzing the thermal performance
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