Thermal Performance of a Tube Equipped with V-nozzle Turbulator Inserts

Öz

This study pertains to the numerical investigation of the influence of V-nozzle turbulators on thermal performance in a circular tube under uniform heat flux condition. The converging-diverging nozzles as a venturi structure were located in the test tube in order to generate turbulance/reverseflow. The computations were carried out by consideration of various pitch ratios, PR = 2, 4, and 6 for Reynolds numbers between 5000 and 32000, using air as a working fluid. The variation of Nusselt number (Nu) and friction factor (f) versus Reynolds number (Re) were introduced for the obtained numerical results. The plain tube results were compared with the works available in literature for confirmation of the used numerical method. Consequently, the results demonstrated that the usage of V-nozzles at smaller pitch ratio yielded an increase in heat transfer rate and pressure loss.

Anahtar Kelimeler

• V-nozzle,Turbulent flow,Thermal performance

V-Lüle Türbülator Yerleştirilen Bir Borunun Termal Performansı

Öz

Bu çalışma da sabit ısı akısı uygulanan silindirik bir boru içerisindeki V-lüle türbülatörlerin ısıl performansa etkisi sayısal olarak incelenmiştir. Ventüri yapısına benzer ıraksak ve yakınsak lüleler test borusu içerisine türbülans/tersakış oluşturmak amacıyla yerleştirilmiştir. Hesaplamalar PR=2,4 ve 6 Reynolds sayısının ise 5000 ile 32000 aralığında değiştiği farklı değerlerde hava akışkanı kullanılarak gerçekleştirilmiştir. Elde edilen sayısal sonuçlar için Nusselt sayısı (Nu) ve sürtünme faktörü (f) ile Reynolds sayısı (Re) arasındaki değişim ortaya konulmuştur. Boş boru sonuçları, kullanılan sayısal yöntemin doğrulanması için literatürde bulunan diğer çalışmalar karşılaştırılmıştır. Sonuç olarak, elde edilen sonuçlar daha küçük hatve oranında V-lüle kullanımının ısı transferi miktarında ve basınç kaybında bir artış sağladığını göstermiştir.

Anahtar Kelimeler

• V-lüle,Türbülanslı akış,Isıl performans

Kaynakça

1. Eimsa-ard, S. and Promvonge, P.(2006), “Experimental Investigation of Heat Transfer and Friction Characteristics in a Circular Tube Fitted with V-nozzle Turbulators”, Int Commun Heat Mass Transfer, (33), 591–600.
2. [Shoji, Y., Sato, K., and Oliver D.R.(2003), “Heat Transfer Enhancement in Round Tube using Wire Coil Influence of Length and Segmentation”, Heat Transfer-Asian Res, (32), 99-107.
3. Zimparov, V. (2001), “Enhancement of Heat Transfer by a Combination of Three-Start Spirally Corrugated Tubes with a Twisted Tape”, Int J Heat Mass Transfer,( 44), 551–574.
4. Tandiroglu, A., and Ayhan, T.(2006), “Energy Dissipation Analysis of Transient Heat Transfer for Turbulent Flow in a Circular Tube with Baffle Inserts”, Appl Therm Eng, (26),178–185.
5. Yakut, K., Alemdaroglu, N., Sahin, B.,and Celik, C.(2006), “Optimum Design Parameters of a Heat Exchanger Having Hexagonal Fins”, Appl Energy, (83), 82–98.
6. Zhang, Z., Yu, Z. and Fang, X.(2007), “An Experimental Heat Transfer Study for Helically Flowing Outside Petal-Shaped Finned Tubes with Different Geometrical Parameters”, Appl Therm Eng, (27), 268–272.
7. Tijing, L.D., Pak, B.C., Baek, B.J. and Lee, D.H.(2006), “A Study on Heat Transfer Enhancement Using Straight and Twisted Internal Fins”, Int Commun Heat Mass Transfer, (33), 719–726.
8. Eimsa-ard, S., Thianpong, C. and Promvonge, P.(2006), “Experimental Investigation of Heat Transfer and Flow Friction in a Circular Tube Fitted with Regularly Spaced Twisted Tape Elements”, Int Commun Heat Mass Transfer, (33), 1225–1233.

9. Chang, S.W., Jan, Y.J. and Liou, J.S.(2007), “Turbulent Heat Transfer and Pressure Drop in Tube Fitted with Serrated Twisted Tape”, Int J Therm Sci, (46), 506–518.
10. Shaikh, N. and Siddiqui, M.H.K.(2007), “Heat Transfer Augmentation in a Heat Exchanger Tube Using a Baffle”, Int J Heat Fluid Flow, (28), 318–28.
11. Naphon, P.(2006), “Effect of Coil-Wire Insert on Heat Transfer Enhancement and Pressure Drop of Horizontal Concentric Tubes”, Int Commun Heat Mass Transfer, (33), 753–763.
12. Buchlin, J.M.(2002), “Convective Heat Transfer in a Channel with Perforated Ribs”, Int J Therm Sci, (41), 332–340.
13. Tanda, G.(2004), “Heat transfer in Rectangular Channels with Transverse and V-shaped Broken Ribs”, Int J Heat Mass Transfer, (47), 229–43.
14. Jordan, S.A.(2003), “The Turbulent Character and Pressure Loss Produced by Symmetric Ribs in a Circular Duct”, Int J Heat Fluid Flow, (24), 795–806.
15. San, J.Y. and Huang, W.C.(2006), “Heat Transfer Enhancement of Transverse Ribs in Circular Tubes with Consideration of Entrance Effect”, Int J Heat Mass Transfer, (49), 2965–2971.
16. Lu, B. and Jiang, P.X.(2006), “Experimental and Numerical Investigation of Convection Heat Transfer in a Rectangular Channel with Angled Ribs”, Exp Therm Fluid Sci, (30),513–521.
17. Tanda, G.(2001), “Heat Transfer and Pressure Drop in a Rectangular Channel with Diamond-Shaped Elements”, Int J Heat Mass Transfer, (49), 3529–3541.
18. Sahin, B. and Demir, A.(2008), “Performance Analysis of a Heat Exchanger Having Perforated Square Fins”, Appl Therm Eng, (28), 621–632.
19. Dhir, V.K., Chang, F. and Yu, J.(1990), “Enhancement of Single Phase Forced Convection Heat Transfer in Tubes Using Staged Tangential Flow Injection”, Final Report, June 1987–December 1989, GRI-90/0134.
20. Dhir, V.K. and Chang, F.(1992), “Heat Transfer Enhancement Using Tangential Injection”, ASHRAE Transactions (98), BA-92-4-1.
21. G. Son, V.K. Dhir (1993), Enhancement of heat transfer in an annulus using tangential flow injection, Trans ASME Journal Heat Transfer, (246), 59–66.
22. Yılmaz, M., Comaklı, O. and Yapıcı, S. (1999), “Enhancement of Heat Transfer by Turbulent Decaying Swirl Flow”, Energy Conversion Management, (40), 1365–1376.
23. Yılmaz, M., Comaklı, O. and Yapıcı, S. and Sara, O.N. (2003), “Heat Transfer and Friction Characteristics in Decaying Swirl Flow Generated by Different Radial Guide Vane Swirl Generators”, Energy Conversion and Management, (44), 283–300.
24. Menter, F.R. , (1994), “Two-equation Eddy-Viscosity Turbulence Models For Engineering Applications”, American Institute of Aeronautics and Astronautics, (32), 283–300.