Abstract
This paper reports numerical investigations of heat transfer and friction factor characteristics in swirling flow conditions using CFD simulation. A commercial CFD package, FLUENT 6.3.26, was used in this study. 3D models for circular tube fitted with classical and quadrant-cut twisted tape (QCT) inserts with three twist ratios (y= 2.93, 3.91, and 4.89) and different cut depths (w= 0.5, 1.0, and 1.5 cm) were generated for the simulation. The data obtained from the CFD simulation were verified with the literature correlations of plain tube with the discrepancy of less than ±8% for Nusselt number and ±10% for friction factor. The results show that there was a significant increase in heat transfer coefficient and friction factor in the tube fitted with quadrant-cut twisted tape (QCT) with decreasing of twist ratio (y) and cut depth (w). Furthermore, the configuration of QCT insert with a twist ratio ofy= 2.93 and a cut depth ofw= 0.5 cm offered higher heat transfer rate and friction factor than other twist ratios.
Highlights
The performance of heat exchangers especially for singlephase flows can be enhanced by many augmentation techniques
The results show that there was a significant increase in heat transfer coefficient and friction factor in the tube fitted with quadrant-cut twisted tape (QCT) with decreasing of twist ratio (y) and cut depth (w)
Nagarajan and Sivashanmugam [20] reported the simulation of heat transfer augmentation and Mathematical Problems in Engineering friction factor characteristics of a circular tube fitted with a right-left helical twist insert with a 100 mm spacer using computational fluid dynamics (CFD)
Summary
The performance of heat exchangers especially for singlephase flows can be enhanced by many augmentation techniques. Kumar et al [16] studied the hydrodynamics and heat transfer characteristics of tube in a pilot scale helical heat exchanger fitted with semicircular plate in the annular area using a commercial CFD package to predict the flow and thermal properties in the heat exchanger tube They found that the Nusselt number and friction factor in the inner and outer tubes from the CFD results coincided with the experimental data. Shabanian et al [21] conducted an experiment and (CFD) modeling on heat transfer, friction factor, and thermal performance of an air cooled heat exchanger equipped with three types of tube insert including butterfly, classic, and jagged twisted tape They found that the predicted results in terms of turbulence intensity are in good agreement with measured values of Nusselt number and friction factor.
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