ENHANCEMENT STUDY OF AIR-SIDE HEAT TRANSFER IN HVAC&R HEAT EXCHANGERS USING WINGLET VORTEX GENERATORS

A comprehensive computational investigation has been carried out to evaluate the thermo-fluid performance of a fin-and-tube heat exchanger enhanced with plane and wavy rectangular winglet pairs. Based on the numerical analysis, the following key conclusions are drawn: The use of vortex generators significantly enhances heat transfer performance by inducing longitudinal vortices, which improve fluid mixing and reduce thermal boundary layer thickness.For plane rectangular winglet pairs, the thermo-fluid performance is strongly influenced by geometric parameters such as number of winglets, placement, and angle of attack. An optimal configuration of four winglet pairs, stream-wise distance ΔX = 4.268 mm, and angle of attack β = 15° provides the best performance, achieving approximately 21–22% enhancement over the baseline case.Wavy rectangular winglet pairs further improve heat transfer performance by generating stronger and more distributed vortices. The optimal parameters are identified as wave number n = 6, wave height Wh = 0.9 mm, winglet length l = 30 mm, and angle of attack β = 15°.The combined configuration of plane and wavy winglets enhances thermo-fluid performance beyond individual configurations. The P2W3 arrangement (plane winglet at tube 2 and wavy winglet at tube 3) yields the highest overall enhancement of approximately 21%.Although heat transfer enhancement is achieved, an increase in pressure drop is observed for all winglet configurations. However, optimized designs ensure that the improvement in heat transfer outweighs the pressure penalty.The developed empirical correlations for Nusselt number, friction factor, and enhancement factor show good agreement with numerical results, with deviations within acceptable limits.Overall, the study confirms that optimized vortex generator configurations are an effective and practical approach for enhancing the performance of compact fin-and-tube heat exchangers.

Experimental Validation: Conduct experimental studies to validate the numerical results and verify the performance of optimized winglet configurations under real operating conditions.Turbulent Flow Analysis: Extend the present study to higher Reynolds numbers and turbulent flow regimes to evaluate performance under practical industrial conditions.Alternative Tube Arrangements: Investigate the performance of vortex generators in staggered tube configurations and compare with inline arrangements.Advanced Winglet Geometries: Explore innovative vortex generator designs such as perforated, curved, split, or hybrid winglets for further enhancement.Nanofluids and Advanced Working Fluids: Study the effect of using nanofluids or other advanced fluids to improve heat transfer performance in combination with vortex generators.Optimization Techniques: Apply optimization algorithms (e.g., genetic algorithms, machine learning approaches) to identify globally optimal configurations considering multiple design parameters.Multi-Objective Analysis: Perform multi-objective optimization considering heat transfer, pressure drop, cost, and energy efficiency simultaneously.REFERENCES   1.         Shah, R.K. and Sekulic, D.P. (2002). Fundamentals of Heat Exchanger Design. Wiley, New Jersey. 2.         Webb, R.L. and Kim, N.H. (2005). Principles of Enhanced Heat Transfer, 2nd Edition. Taylor & Francis, New York. 3.         Edwards, F.J. and Alker, C.J.R. (1974). The improvement of forced convection surface heat transfer using surface protrusions in the form of (a) cubes and (b) vortex generators. Proceedings of the 5th International Heat Transfer Conference, Tokyo, 2, 244–248. 4.         Turk, A.Y. and Junkhan, G.H. (1986). Heat transfer enhancement downstream of vortices in a channel flow. Proceedings of the 8th International Heat Transfer Conference, San Francisco, 6, 2903–2908. 5.         Fiebig, M., Valencia, A. and Mitra, N.K. (1991). Wing-type vortex generators for fin-and-tube heat exchangers. Experimental Thermal and Fluid Science, 4, 275–283. 6.         Tiggelbeck, S., Mitra, N.K. and Fiebig, M. (1992). Flow structure and heat transfer in a channel with multiple longitudinal vortex generators. Experimental Thermal and Fluid Science, 5(4), 425–436. 7.         Tiggelbeck, S., Mitra, N.K. and Fiebig, M. (1994). Comparison of wing-type vortex generators for heat transfer enhancement in channel flows. Journal of Heat Transfer, 116(4), 880–885. 8.         Fiebig, M. (1995). Embedded vortices in internal flow: heat transfer and pressure loss enhancement. International Journal of Heat and Fluid Flow, 16(5), 376–388. 9.         Biswas, G., Torii, K., Fujii, D. and Nishino, K. (1996). Numerical and experimental determination of flow structure and heat transfer effects of longitudinal vortices in a channel flow. International Journal of Heat and Mass Transfer, 39(16), 3441–3451. 10.     Sohankar, A. and Davidson, L. (2001). Effect of inclined vortex generators on heat transfer enhancement in a three-dimensional channel. Numerical Heat Transfer Part A, 39(5), 433–448.