Thermo-Hydraulic Performance Optimization of Intrusion-Type Curved Fins in Tube-Bank Heat Exchangers Using Response Surface Methodology

Abstract

Flow separation and wake formation around circular tubes are among the primary causes of pressure losses and limited heat transfer performance in tube-bank heat exchangers (TBHEs). In this study, the thermo-hydraulic performance of a staggered circular tube-bank heat exchanger enhanced with a novel Inward Curved Ring-Winglet (ICRW) configuration was numerically investigated. Unlike conventional external fins that primarily increase surface area, the proposed intrusion-type design modified the core flow by partially penetrating into the channel region, promoting longitudinal vortex formation while suppressing wake recirculation. A three-dimensional steady-state CFD framework was developed in ANSYS Fluent using the RNG k–ε turbulence model to analyze airflow and heat transfer characteristics. The effects of four geometric parameters, namely winglet length (L), winglet gap (G), inclination angle (θ), and channel height (H), together with the Reynolds number (Re), were systematically examined using Response Surface Methodology (RSM). A Central Composite Design–based RSM framework was employed to construct surrogate models and identify the optimal design by maximizing the thermo-hydraulic performance factor (TPF). The performance evaluation was based on the TPF, which accounts for both Colburn j-factor and friction factor. The investigated parameter ranges were L = 12.5–22.5 mm, G = 0.75–2.25 mm, θ = 3.75°–15°, H = 3.125–12.5 mm, and Re = 1100–11500. The RSM analysis identified an optimal configuration at L = 22.105 mm, G = 2.10 mm, θ = 5.12°, and H = 3.14 mm, for which the maximum TPF of 1.53 was achieved at Re = 11239. Compared to the baseline tube-bank configuration, the optimized ICRW design significantly enhances heat transfer while maintaining acceptable pressure losses. Flow visualization results indicate that the improvement is mainly attributed to intensified longitudinal vortex structures and effective disruption of thermal boundary layers. The results demonstrate that intrusion-type ICRW fins provide a compact and effective passive enhancement strategy for high-performance air-side TBHE applications.

Keywords

• Tube-bank heat exchanger
• intrusion-type fin
• CFD
• Response surface method

Response Surface Methodology Kullanılarak Boru Demeti Isı Değiştiricilerinde İçe Doğru Kıvrımlı Kanatçıkların Termo-Hidrolik Performans Optimizasyonu

Abstract

Bu çalışmada, içe doğru kıvrımlı halka-kanatçık (Inward Curved Ring-Winglet, ICRW) konfigürasyonu ile geliştirilmiş dairesel ve şaşırtmalı bir boru demeti ısı değiştiricisinin termo-hidrolik performansı sayısal olarak incelenmiştir. Yüzey alanını artırmaya odaklanan geleneksel dışa doğru büyüyen kanatçık tasarımlarının aksine, önerilen bu içe doğru uzanan (intrusion-type) yapı, akış kanalının çekirdek bölgesine kısmen nüfuz ederek ana akışı doğrudan değiştirmekte; boyuna girdap oluşumunu teşvik ederken iz bölgesi geri dolaşımını baskılamaktadır. Hava akışı ve ısı transferi özelliklerini analiz etmek amacıyla, RNG k–ε türbülans modeli kullanılarak ANSYS Fluent ortamında üç boyutlu, kararlı durumlu bir HAD çerçevesi oluşturulmuştur. Kanatçık uzunluğu (L), kanatçık aralığı (G), eğim açısı (θ) ve kanal yüksekliği (H) olmak üzere dört temel geometrik parametrenin yanı sıra Reynolds sayısının (Re) etkileri, Yanıt Yüzey Yöntemi (Response Surface Methodology, RSM) kullanılarak sistematik biçimde değerlendirilmiştir. Performans değerlendirmesi, Colburn j faktörü ile sürtünme faktörünü birlikte dikkate alan termo-hidrolik performans faktörü (TPF) esas alınarak gerçekleştirilmiştir. İncelenen parametre aralıkları L = 12.5–22.5 mm, G = 0.75–2.25 mm, θ = 3.75°–15°, H = 3.125–12.5 mm ve Re = 1100–11500 olarak belirlenmiştir. RSM analizi sonucunda, L = 22.105 mm, G = 2.10 mm, θ = 5.12° ve H = 3.14 mm geometrik ölçülerinde, Re = 11239 için maksimum TPF değeri 1.53 olarak elde edilmiştir. Temel boru demeti konfigürasyonu ile karşılaştırıldığında, optimize edilmiş ICRW tasarımı ısı transferini belirgin biçimde artırırken kabul edilebilir basınç kayıplarını korumaktadır. Akış görselleştirme sonuçları, performans iyileşmesinin temel olarak güçlenen boyuna girdap yapıları ve termal sınır tabakasının etkin biçimde bozulmasından kaynaklandığını göstermektedir. Elde edilen bulgular, içe doğru uzanan ICRW kanatçıklarının yüksek performanslı boru demeti ısı değiştiricileri için kompakt ve etkili bir pasif iyileştirme stratejisi sunduğunu ortaya koymaktadır.

Keywords

• Boru demetli ısı değiştirici
• içe doğru kanatçık
• HAD
• yanıt yüzey yöntemi
• pasif ısı transferi artırımı

References

1. Chen, X., Yao, S., Wang, J., Wang, C., & Zhen, M. (2025). Analysis of heat storage performance of horizontally placed triplex-tube heat exchanger with corrugated fins. International Journal of Heat and Fluid Flow, 115, Article 109875. https://doi.org/10.1016/j.ijheatfluidflow.2025.109875
2. Deeb, R. (2022). Flow and heat transfer characteristics of staggered mixed circular and drop-shaped tube bundle. Physics of Fluids, 34(6), Article 065126. https://doi.org/10.1063/5.0090732
3. Deeb, R. (2023). Enhancing heat exchanger performance through hybrid angle of attack control for drop-shaped tubes. Physics of Fluids, 35(8), Article 085122. https://doi.org/10.1063/5.0160385
4. Elmekawy, A. M. N., Ibrahim, A. A., Shahin, A. M., Al-Ali, S., & Hassan, G. E. (2021). Performance enhancement for tube bank staggered configuration heat exchanger – CFD study. Chemical Engineering and Processing - Process Intensification, 164, Article 108392. https://doi.org/10.1016/j.cep.2021.108392
5. He, Y.-L., Chu, P., Tao, W.-Q., Zhang, Y.-W., & Xie, T. (2013). Analysis of heat transfer and pressure drop for fin-and-tube heat exchangers with rectangular winglet-type vortex generators. Applied Thermal Engineering, 61(2), 770–783. https://doi.org/10.1016/j.applthermaleng.2012.02.040
6. Keawkamrop, T., Asirvatham, L. G., Dalkılıç, A. S., Ahn, H. S., Mahian, O., & Wongwises, S. (2021). An experimental investigation of the air-side performance of crimped spiral fin-and-tube heat exchangers with a small tube diameter. International Journal of Heat and Mass Transfer, 178, Article 121571. https://doi.org/10.1016/j.ijheatmasstransfer.2021.121571
7. Kumar, A., Joshi, J. B., & Nayak, A. K. (2017). A comparison of thermal-hydraulic performance of various fin patterns using 3D CFD simulations. International Journal of Heat and Mass Transfer, 109, 336–356. https://doi.org/10.1016/j.ijheatmasstransfer.2017.01.102
8. Lee, M. S., Gwon, J. G., Seo, Y. M., Choi, H. K., & Park, Y. G. (2025). Ellipsoidal protrusions for enhanced thermal performance in fin-tube heat exchangers. Case Studies in Thermal Engineering, 74, Article 106770. https://doi.org/10.1016/j.csite.2025.106770

9. Lemouedda, A., Schmid, A., Franz, E., Breuer, M., & Delgado, A. (2011). Numerical investigations for the optimization of serrated finned-tube heat exchangers. Applied Thermal Engineering, 31(8–9), 1393–1401. https://doi.org/10.1016/j.applthermaleng.2010.12.035
10. Lin, Z. M., Li, S. F., Liu, C. P., Wang, L. B., & Zhang, Y. H. (2021). Thermal and flow characteristics of a channel formed by aligned round tube bank fins stamped with curve delta-winglet vortex generators. Thermal Science and Engineering Progress, 26, Article 101113. https://doi.org/10.1016/j.tsep.2021.101113
11. Lin, Z.-M., Yang, R.-X., Hou, J.-C., Hou, B., & Wang, L.-B. (2025). Dynamic vortex characteristics and their contribution to heat transfer enhancement in the channel of a serrated finned tube heat exchanger. Case Studies in Thermal Engineering, 73, Article 106560. https://doi.org/10.1016/j.csite.2025.106560
12. Lotfi, B., & Sundén, B. (2020). Development of new finned tube heat exchanger: Innovative tube-bank design and thermohydraulic performance. Heat Transfer Engineering, 41(14), 1209–1231. https://doi.org/10.1080/01457632.2019.1637112
13. Lu, G., & Zhou, G. (2016). Numerical simulation on performances of plane and curved winglet type vortex generator pairs with punched holes. International Journal of Heat and Mass Transfer, 102, 679–690. https://doi.org/10.1016/j.ijheatmasstransfer.2016.06.063
14. Mangrulkar, C. K., Abraham, J. D., & Dhoble, A. S. (2019). Numerical studies on the near wall y+ effect on heat and flow characteristics of the cross flow tube bank. Journal of Physics: Conference Series, 1240(1), Article 012110. https://doi.org/10.1088/1742-6596/1240/1/012110
15. Mangrulkar, C. K., Dhoble, A. S., Abraham, J. D., & Chamoli, S. (2020). Experimental and numerical investigations for effect of longitudinal splitter plate configuration for thermal-hydraulic performance of staggered tube bank. International Journal of Heat and Mass Transfer, 161, Article 120280. https://doi.org/10.1016/j.ijheatmasstransfer.2020.120280
16. Mangrulkar, C. K., Dhoble, A. S., Chakrabarty, S. G., & Wankhede, U. S. (2017). Experimental and CFD prediction of heat transfer and friction factor characteristics in cross flow tube bank with integral splitter plate. International Journal of Heat and Mass Transfer, 104, 964–978. https://doi.org/10.1016/j.ijheatmasstransfer.2016.09.013
17. Safwat Wilson, A., & Khalil Bassiouny, M. (2000). Modeling of heat transfer for flow across tube banks. Chemical Engineering and Processing: Process Intensification, 39(1), 1–14. https://doi.org/10.1016/S0255-2701(99)00069-0
18. Song, K., Xi, Z., Su, M., Wang, L., Wu, X., & Wang, L. (2017). Effect of geometric size of curved delta winglet vortex generators and tube pitch on heat transfer characteristics of fin-tube heat exchanger. Experimental Thermal and Fluid Science, 82, 8–18. https://doi.org/10.1016/j.expthermflusci.2016.11.002
19. Szydłowski, M., & Gutkowski, A. (2025). Numerical analysis of heat exchanger with inclined finned semicircular tubes. International Communications in Heat and Mass Transfer, 160, Article 108326. https://doi.org/10.1016/j.icheatmasstransfer.2024.108326
20. Tepe, A. Ü., & Yilmaz, H. (2022). Thermal–hydraulic performance of the circular-slice-shaped-winglet for tube bank heat exchanger. International Journal of Thermal Sciences, 179, Article 107711. https://doi.org/10.1016/j.ijthermalsci.2022.107711
21. Tian, K., Guo, Z., Ma, T., Zeng, M., & Wang, J. (2024). Numerical investigation on ash accumulation characteristics of serrated spiral finned tube heat exchanger in waste heat utilization. Applied Thermal Engineering, 250, Article 123512. https://doi.org/10.1016/j.applthermaleng.2024.123512
22. Wang, M., & Wang, J. (2025). Enhanced heat extraction for coaxial medium-deep borehole heat exchangers by adding triangular fins on the outer tube wall. Renewable Energy, 242, Article 122448. https://doi.org/10.1016/j.renene.2025.122448
23. White, J. (2016). CFD simulation and experimental analyses of a copper wire woven heat exchanger design to improve heat transfer and reduce the size of adsorption beds. Computation, 4(1), Article 8. https://doi.org/10.3390/computation4010008
24. Yalçınkaya, O., & Tepe, A. Ü. (2026). Numerical assessment of alternative cross-sectional tube geometries for enhanced thermohydraulic performance of tube bank heat exchanger. International Journal of Thermal Sciences, 223, Article 110602. https://doi.org/10.1016/j.ijthermalsci.2025.110602
25. Žukauskas, A. (1972). Heat transfer from tubes in crossflow. Advances in Heat Transfer, 8, 93–160. https://doi.org/10.1016/S0065-2717(08)70038-8