Heat Transfer and Flow Characteristics Through Acentric Twisted Oval Tubes: A 3D Numerical Investigation

Authors

• Mohsen H. Fagr, Mechanical Engineering Department, College of Engineering, University of Thi-Qar, Nasiriyah, Iraq
• Karim Egab, Mechanical Engineering Department, College of Engineering, University of Thi-Qar, Nasiriyah, Iraq
• Hayder M. Hasan, Shatrah Technical College, Southern Technical University, IraqFollow

Abstract

Tube oval- twisting techniques have been consistently used to promote heat transfer and flow turbulence properties within tubes, enhancing flow mixing, disturbing boundary layers, and hence, offering higher thermal efficiency. However, the acentric twisted oval tubes have more intricacy as compared with twisted oval tubes due to the eccentricity of their twisting pattern and using them in heat transfer. The current study performs 8 configurations of the acentric twisted heating oval tube that is exposed to a constant heat flux of 1750W/m². In addition, 2 cases of the typical centric twisted oval and plain circular tubes for comparison purposes under a turbulent flow regime, 10000 ≤ Re ≤ 50000. The momentum, continuity and energy equations were solved by the chosen RNG k-ε model. The main parameters of Nusselt number Nu, friction factor f and thermal performance factor TPF for the air flows are examined at various aspect and eccentricity ratios. The results are compared to each other in all cases and with the typical plain tube and the well-established centric twisted oval tube. The results show a maximum increase in Nusselt number and friction factor of 196% and 182%, respectively, more than those of the plain tube. The acentric twisted oval tubes provide better thermal performance with an optimal value of TPF=1.61, which is 61% higher than the plain tube. The Nusselt number is almost 30% greater than that of the typical centric twisted oval tube, and the thermal performance factor is (TPF=1.24) at the same conditions. This valuable enhancement may support the heat exchanger industry, boosting energy savings and carbon dioxide emissions.

Recommended Citation

Fagr, Mohsen H.; Egab, Karim; and Hasan, Hayder M. (2026) "Heat Transfer and Flow Characteristics Through Acentric Twisted Oval Tubes: A 3D Numerical Investigation," Al-Bahir: Vol. 9: Iss. 2, Article 9.
Available at: https://doi.org/10.55810/2313-0083.1150

References

[1] Fagr MH, Hasan HM, Alsulaiei ZM. Effects of acentric twisted tape on heat transfer and flow in tubes. Case Stud Therm Eng 2025;75:107263. https://doi.org/10.1016/j.csite.2025.107263.

[2] Azizi AS, Mousavi SM, Vafai K, Darzi AR. Comprehensive review of heat transfer and fluid flow characteristics of elliptical/oval twisted tubes. Int J Heat Fluid Flow 2024;112: 109639. https://doi.org/10.1016/j.ijheatfluidflow.2024.109639.

[3] Alsulaiei ZM, Fagr MH, Hasan HM. Investigation of How Cooling the Compressor Inlet in a Gas Turbine Cycle with Thermal Storage Affects the Cycle's Thermal Performance. Int J Heat Technol 2025;43(1). https://doi.org/10.18280/ijht.430120.

[4] Hossain F, Karim MR, Bhuiyan AA. A review on recent advancements of the usage of nano fluid in hybrid photovoltaic/thermal (PV/T) solar systems. Renew Energy 2022; 188:114—31. https://doi.org/10.1016/j.renene.2022.01.116.

[5] Promvonge Pongjet, Promthaisong Pitak, Skullong Sompol, Nakhchi Mahdi Erfanian. Thermal effectiveness enhancement in heat exchange tube using louver-punched V-baffles. Int J Heat Mass Tran 2024;225:125411. https://doi.org/ 10.1016/j.ijheatmasstransfer.2024.125411.

[6] Wang Zilong, Liu Xiandong, Yang Fu, Ye Yanghui, Dong Cong, Shen Jinjian. Numerical investigation on enhanced thermal performance of a novel inclination baffle heat exchanger: Effects of overflow orifice, inclination angle and nanofluid. Int J Heat Mass Tran 2026;258:128257. https:// doi.org/10.1016/j.ijheatmasstransfer.2025.128257.

[7] Shen Wenpeng, Xu Xiangjiang, Zhang Xiancheng, Tang Peishuo, Song Wei. Design and analysis of bionic baffles for coupled thermal and dynamic performance enhancement in shell-and-tube heat exchangers. Int J Therm Sci 2026;224: 110677. https://doi.org/10.1016/j.ijthermalsci.2026.110677.

[8] Zhu X, Lu Q, Xue Q, Cheng Y, Jiao X, Wang H. Analysis and optimization on flow and heat transfer characteristics of twisted oval shell-and-tube heat exchangers based on numerical simulation and model prediction. Int Commun Heat Mass Tran 2025;165:109077. https://doi.org/10.1016/ j.icheatmasstransfer.2025.109077.

[9] Nuhash MM, Alam MI, Zihad A, Hasan MJ, Duan F, Bhuiyan AA, Karim MR. Enhancing energy harvesting performance of a flat plate solar collector through integrated carbon-based and metal-based nanofluids. Results Eng 2023; 19:101276. https://doi.org/10.1016/j.rineng.2023.101276.

[10] Ratul RE, Ahmed F, Alam S, Karim MR, Bhuiyan AA. Numerical study of turbulent flow and heat transfer in a novel design of serpentine channel coupled with D-shaped jaggedness using hybrid nanofluid. Alex Eng J 2023;68:647—63. https://doi.org/10.1016/j.aej.2023.01.061.

[11] Sadeghianjahromi A, Wang C. Heat transfer enhancement in fin-and-tube heat exchangers — A review on different mechanisms. Renew Sustain Energy Rev 2020;137:110470. https://doi.org/10.1016/j.rser.2020.110470.

[12] Feng Z, Xin C, Zhou T, Zhang J, Fu T. Airside thermal-hydraulic and fouling performances of economizers with integrally-molded spiral finned tubes for residual heat recovery. Appl Therm Eng 2022;211:118365. https://doi.org/ 10.1016/j.applthermaleng.2022.118365.

[13] Tang S, Xie X, Zhao Z, Ding L. Investigation of thermal-hydraulic characteristics in a novel finned tube heat exchanger for flue gas waste heat recovery. Case Stud Therm Eng 2022;39: 102392. https://doi.org/10.1016/j.csite.2022.102392.

[14] Chen Z, Cheng M, Liao Q, Ding Y, Zhang J. Experimental investigation on the air-side flow and heat transfer characteristics of 3-D finned tube bundle. Int J Heat Mass Tran 2018;131:506—16. https://doi.org/10.1016/j.ijheatmasstransf er.2018.10.026.

[15] Unger S, Beyer M, Pietruske H, Szalinski L, Hampel U. Air-side heat transfer and flow characteristics of additively manufactured finned tubes in staggered arrangement. Int J Therm Sci 2020;161:106752. https://doi.org/ 10.1016/j.ijthermalsci.2020.106752.

[16] Zhong J, Wang Y, Li M, Pei G, Tang S, Rong J, Xu C, Kang L, Deng J, Shan S, Zhou L. Heat transfer characteristics of the fin-tube three-fluid heat exchanger in cold warehouse with cold storage. Energy 2026;347:140362. https://doi.org/ 10.1016/j.energy.2026.140362.

[17] Chang X, Wu X, He A, Chen L, Ding F, Song K. Flow and heat transfer characteristics of a novel m-shaped corrugated fin-and-tube heat exchanger with curved vortex generators. Int Commun Heat Mass Tran 2026;172:110567. https:// doi.org/10.1016/j.icheatmasstransfer.2026.110567.

[18] Hu W, Ye W, Guan Y, Zhang X, Jiang C, Li Z. Enhancing the thermal hydraulic performance on the air side of finnedtube heat exchangers through superhydrophilic—superhydrophobic striped patterns. Therm Sci Eng Prog 2026;70:104503. https://doi.org/10.1016/ j.tsep.2026.104503.

[19] Chimres N, Kaew-On J, Surapapwong T, Wongwises S. Comparative performance analysis of metal foam and spiral fin-and-tube heat exchangers. Results Eng 2026;29:109013. https://doi.org/10.1016/j.rineng.2026.109013.

[20] Hasan H, Egab K, Hassan H. Thermal and hydraulic characteristics study of different dimpled micro-channel heat sinks. AIP Conf Proc 2021;2404:080009. https://doi.org/ 10.1063/5.0069070.

[21] Mehrjardi SaA, Mazaheri K, Khademi A. Integerated optimization and advanced thermal assesment of nanofluidassisted and dimple-enhanced shell-and-tube heat exchangers. Therm Sci Eng Prog 2025;69:104429. https:// doi.org/10.1016/j.tsep.2025.104429.

[22] Okab AK, Hasan HM, Hamzah M, Egab K, Al-Manea A, Yusaf T. Analysis of heat transfer and fluid flow in a microchannel heat sink with sidewall dimples and fillet profile. Int J Thermofluids 2022;15:100192. https://doi.org/ 10.1016/j.ijft.2022.100192.

[23] Egab K, Oudah SK, Al-Manea A, Hasan H, Arõcõ M. Thermal performance evaluation of U-shaped obstacles with rectangle perforation in solar air heater. Case Stud Therm Eng 2025;75: 107127. https://doi.org/10.1016/j.csite.2025.107127.

[24] Fagr MH, Hasan HM, Alsulaiei ZMA. Enhancing Heat Transfer Using Multi-Size Teardrops obstacles. Thi-Qar Univers J Eng Sci 2022;12(1):7—14. https://doi.org/10.31663/ tqujes.12.1.404 (2022).

[25] Abouzied AS, Basem A, Balla HHA, Alkhatib OJ, Sinnah ZaB, Elmonser H, Abduvalieva D, Albalawi H, Alansari AM, Mahariq I. Numerical simulation and machine learning modeling of tubular solar air heaters enhanced with twisted tape inserts. Appl Therm Eng 2026;290:130176. https://doi.org/ 10.1016/j.applthermaleng.2026.130176.

[26] Rathaur DK, Sarviya R, Rajput S. Synergistic enhancement of heat transfer in tubular heat exchangers using twisted tape inserts and nanofluids: An integrated numerical and experimental review. Int J Heat Fluid Flow 2025;118:110180. https://doi.org/10.1016/j.ijheatfluidflow.2025.110180.

[27] Alfaro-Lopez  M, Castro-García M, Valera-Jimenez  J, MarínRueda J, Almendros-Ibanez ~ J, Corcoles J. Experimental study of a double tube heat exchanger with 3D-printed twisted tapes. Appl Therm Eng 2025;285:129288. https:// doi.org/10.1016/j.applthermaleng.2025.129288.

[28] Wongcharee K, Chuwattanakul V, Chamoli S, Maruyama N, Hirota M, Eiamsa-Ard S. Investigation of turbulent thermalhydraulic behaviors of a heat exchanger tube with U-cut twisted-tape. Case Stud Therm Eng 2025:105838. https:// doi.org/10.1016/j.csite.2025.105838.

[29] Singh SK, Kacker R, Chaurasiya PK, Gautam SS. Correlations on heat transfer rate and friction factor of a rectangular toothed v-cut twisted tape exhibiting the combined effects of primary and secondary vortex flows. Int Commun Heat Mass Tran 2022;139:106503. https://doi.org/10.1016/ j.icheatmasstransfer.2022.106503.

[30] Dandoutiya BK, Kumar A. W-cut twisted tape’s effect on the thermal performance of a double pipe heat exchanger: A numerical study. Case Stud Therm Eng 2022;34:102031. https://doi.org/10.1016/j.csite.2022.102031.

[31] Al-Shami KA, Fagr MH. Using different numbers of helical obstacles for promoting heat transfer in the tubes. Chem Prod Process Model 2025;20(6):929—42. https://doi.org/ 10.1515/cppm-2025-0031.

[32] Murtadha, Fagr M, Mekki K. Enhancement of heat transfer numerically by inserting helical coiled wire inside tube flow. Kufa J Eng 2025;16(3):1—21. https://doi.org/10.30572/2018/kje/ 160301.

[33] Al-Shami KA, Fagr MH. Effects of tapered helical obstacles on heat transfer in tubes. Chem Prod Process Model 2025;20(3):355—69. https://doi.org/10.1515/cppm2024-0133.

[34] Fagr MH, Hasan HM, Alsulaiei ZM. Effects of helical obstacle on heat transfer and flow in a tube. Prog Nucl Energy 2021;137: 103735. https://doi.org/10.1016/j.pnucene.2021.103735.

[35] Alsulaiei ZM, Hasan HM, Fagr MH. Flow and heat transfer in obstacled twisted tubes. Case Stud Therm Eng 2021;27: 101286. https://doi.org/10.1016/j.csite.2021.101286.

[36] Mushatet K, Rishakb Q, Fagr M. Numerical study of laminar flow in a sudden expansion obstacled channel. Therm Sci 2013;19(2):657—68. https://doi.org/10.2298/tsci121029105m.

[37] Sabeeh HA, Jaffal HM. Performance analysis of a minichannel heat sink: Effects of helical screw tape inserts. Case Stud Therm Eng 2025;74:106963. https://doi.org/10.1016/ j.csite.2025.106963.

[38] Yao B, Alqahtani AM, Deebani W, Shutaywi M, Ghoushchi S. Improving the thermal performance of the heat exchanger through simultaneous utilization of novel magnetic turbulators and helical coil wire turbulators. Int J Therm Sci 2023;197:108812. https://doi.org/10.1016/ j.ijthermalsci.2023.108812.

[39] Park Y, Chang SH. Swirl flow analysis in a helical wire inserted tube using CFD code. Nucl Eng Des 2010;240(10): 3405—12. https://doi.org/10.1016/j.nucengdes.2010.07.015.

[40] Alsulaiei ZM, Hasan HM, Fagr MH. Modeling the influence of additives and nanoparticles on tubular heat exchanger efficiency utilizing computational fluid dynamics. Int J Heat Technol 2025;43(3):921—9. https://doi.org/10.18280/ijht.430310.

[41] Mirmasoumi S, Behzadmehr A. Effect of nanoparticles mean diameter on mixed convection heat transfer of a nanofluid in a horizontal tube. Int J Heat Fluid Flow 2008;29(2):557—66. https://doi.org/10.1016/j.ijheatfluidflow.2007.11.007.

[42] Akbar NS, Raza M, Ellahi R. Copper oxide nanoparticles analysis with water as base fluid for peristaltic flow in permeable tube with heat transfer. Comput Methods Progr Biomed 2016;130:22—30. https://doi.org/10.1016/ j.cmpb.2016.03.003.

[43] Utomo AT, Haghighi EB, Zavareh AI, Ghanbarpourgeravi M, Poth H, Khodabandeh R, Palm B, Pacek AW. The effect of nanoparticles on laminar heat transfer in a horizontal tube. Int J Heat Mass Tran 2013;69:77—91. https://doi.org/10.1016/ j.ijheatmasstransfer.2013.10.003.

[44] Hosseinzadeh K, Faghiri S, Akbari S, Kermani JR, Jafari B, Shafii MB. Effect of ternary hybrid nanoparticles (GO-MgOTiO2) and radiative heat transfer on the solidification process of PCM inside a triplex tube with hollow fins. Int J Thermofluids 2023;20:100443. https://doi.org/10.1016/ j.ijft.2023.100443.

[45] Lotfizadeh O, Arhamnamazi S, Chowdhury MRH, Kohan M, Aghayari R, Toghraie D, Salahshour S. Heat Transfer Enhancement in Helical Tubes Using Iron Oxide Nanofluid and Spring Turbulators with Different Pitches: Experimental and Neural Network Study. Appl Eng Sci 2026:100303. https://doi.org/10.1016/j.apples.2026.100303.

[46] Sukarman Kristiawan, B, Budiana EP, Khoirudin, Abdulah A. Advanced heat transfer in shell and tube exchangers using TiO2-SiO2 nanofluids. J Eng Res 2026. https://doi.org/10.1016/j.jer.2026.02.016.

[47] Ho JS, Fu M. Laminar flow and heat transfer enhancement in helical twisted tube with twisted tape inserted. Case Stud Therm Eng 2025;76:107310. https://doi.org/10.1016/ j.csite.2025.107310.

[48] Hasan HM, Fagr MH. Study of flow and heat transfer performance in the multi-configuration annulus twisted tube: A three-dimensional numerical investigation. Int J Thermofluids 2024;23:100728. https://doi.org/10.1016/ j.ijft.2024.100728.

[49] Chen W, Dung W. Numerical study on heat transfer characteristics of double tube heat exchangers with alternating horizontal or vertical oval cross section pipes as inner tubes. Energy Convers Manag 2008;49(6):1574—83. https://doi.org/ 10.1016/j.enconman.2007.12.007.

[50] Tang S, Ding L, Wu X, Zhou J, Wang L, Yu Y. Numerical investigation of thermal-hydraulic characteristics in crossflow heat exchangers with different twisted oval tubes. CaseStud Therm Eng 2024;54:104063. https://doi.org/10.1016/ j.csite.2024.104063.

[51] Tan X, Zhu D, Zhou G, Yang L. 3D numerical simulation on the shell side heat transfer and pressure drop performances of twisted oval tube heat exchanger. Int J Heat Mass Tran 2013;65:244—53. https://doi.org/10.1016/j.ijheatmasstransfer.2013.06.011.

[52] Elsayed M, Sultan M, Riaz F, Agrawal MK, Altaf M, Shah NA, Rao BN, Zhang L. A case study on effect of twisting technique on heat transfer characteristics in a twisted oval helical tube. Case Stud Therm Eng 2024;59:104479. https://doi.org/10.1016/ j.csite.2024.104479.

[53] Cheng J, Qian Z, Wang Q. Analysis of heat transfer and flow resistance of twisted oval tube in low Reynolds number flow. Int J Heat Mass Tran 2017;109:761—77. https://doi.org/ 10.1016/j.ijheatmasstransfer.2017.02.061.

[54] Li X, Liu S, Tang S, Mo X, Wang L, Zhu D. Analysis of heat transfer characteristics and entransy evaluation of high viscosity fluid in a novel twisted tube. Appl Therm Eng 2022;210:118388. https://doi.org/10.1016/j.appltherma leng.2022.118388.

[55] Luo C, Song K, Tagawa T, Liu T. Heat Transfer Enhancement in a Novel Annular Tube with Outer Straight and Inner Twisted Oval Tubes. Symmetry 2020;12(8):1213. https://doi.org/10.3390/sym12081213.

[56] Mashayekh K, Etminan A, Pope K, Muzychka YS. Turbulent flow and heat transfer enhancement for straight circular and twisted oval tubes with different dimple shapes. Int J Therm Sci 2025;220:110411. https://doi.org/ 10.1016/j.ijthermalsci.2025.110411.

[57] Kumar KL. Engineering fluid mechanics. Chand Publishing; 2008. ISBN: 81-219-0100-6.

[58] Incropera FP, DeWitt DP. Introduction to heat transfer. John Wiley & Sons; 2002.

[59] Petukhov B. Heat Transfer and Friction in Turbulent Pipe Flow with Variable Physical Properties. In: Advances in heat transfer; 1970. p. 503—64. https://doi.org/10.1016/s0065- 2717(08)70153-9.

[60] Yang S, Zhang L, Xu H. Experimental study on convective heat transfer and flow resistance characteristics of water flow in twisted elliptical tubes. Appl Therm Eng 2011;31(14—15): 2981—91. https://doi.org/10.1016/j.applthermaleng.2011.05.030.