Experimental Investigation of Hybrid Al₂O₃-CuO/Water Nanofluids in Counter Flow Double-pipe Heat Exchangers: Enhanced Heat Transfer Performance for HVAC Applications

Luhaibi, Mohammed Taha; Abedalh, Ayad Suleiman; Soheel, Ammar Hassan

doi:10.22075/jhmtr.2026.39176.1845

Experimental Investigation of Hybrid Al₂O₃-CuO/Water Nanofluids in Counter Flow Double-pipe Heat Exchangers: Enhanced Heat Transfer Performance for HVAC Applications

Document Type : Full Length Research Article

Authors

Mohammed Taha Luhaibi

Ayad Suleiman Abedalh

Ammar Hassan Soheel

Northern Technical University, Engineering Technical College of Mosul, Cultural Group Street, Mosul, Iraq

10.22075/jhmtr.2026.39176.1845

Abstract

The research topic aims to address the urgent need for enhanced energy efficiency in HVAC systems by developing and optimizing efficient heat transfer fluids. Despite the significant attention given to single-component nanofluids, there is a lack of systematic study on the performance of Al2O3-CuO hybrid nanofluids in a double-pipe heat exchanger for HVAC system applications. A comprehensive experimental investigation was done on the various hybrid nanofluid concentrations (0.05%, 0.1%, 0.15%) under different Al₂O₃:CuO ratios (70:30, 60:40, 50:50) at Reynolds numbers 3,000-12,000. Results show that the 60: 40 Al2O3:CuO hybrid nanofluid of 0.1% concentration exhibits a 42.3% enhancement in Nusselt number, a 38.7% increase in heat transfer coefficient, and a 28.4% improvement in thermal effectiveness over that of pure water, with tolerable friction penalties (15-22%). The obtained performance shows a remarkable increase when compared with other published works. The current correlation has a 42.3% higher increase than 13.8% reported by Suresh et al. for Al2O3-Cu and 31% with Madhesh et al. for Cu-TiO2 hybrid nanofluids. The hybrid shows a 35.5% improvement over the single Al2O3 nanofluids and a 13.5% improvement over CuO. A significant increase of 18- 25% is shown in this work as compared to single nanoparticles by using a hybrid system. It can be concluded that in the current research work, the experimental correlations were developed and validated, which could be used to implement the hybrid nanofluids in advanced energy-efficient HVAC systems. Finally, the study has developed and validated experimental correlations that enable the implementation of hybrid nanofluids in advanced HVAC systems to achieve higher energy efficiency.

Keywords

Hybrid nanofluids

Double-pipe heat exchangers

Heat transfer enhancement

HVAC applications

Al₂O₃-CuO nanoparticles

Subjects

Heat exchanger design and testing

[1] Gugulothu, R., and Sanke, N., 2022. Effect of helical baffles and water-based Al₂O₃, CuO, and SiO₂ nanoparticles in the enhancement of thermal performance for shell and tube heat exchanger. Heat Transfer, 51(5), pp. 3768-3793. doi: 10.1002/htj.22474.

[2] Somanchi, N. S., Gugulothu, R., and Tejeswar, S. V., 2024. Experimental investigations on heat transfer enhancement in a double pipe heat exchanger using hybrid nanofluids. Energy Harvesting and Systems, 11(1). doi: 10.1515/ehs-2023-0065.

[3] Bergman, T. L., 2011. Fundamentals of Heat and Mass Transfer. John Wiley & Sons.

[4] Hesselgreaves, J. E., Law, R., and Reay, D., 2016. Compact Heat Exchangers: Selection, Design and Operation. Butterworth-Heinemann.

[5] Abedalh, A., and Mohammed, S., 2023. Numerical investigation thermal performance of solar air heater using different angle V-grooved of corrugated absorber plate. Frontiers in Heat and Mass Transfer, 21, pp. 227-243. doi: 10.32604/fhmt.2023.041777.

[6] Kumar Ahirwar, B., and Kumar, A., 2025. A comprehensive review on heat transfer enhancement in tubular heat exchangers using twisted tapes, wire coil inserts, and their combined effect with nanofluids. Renewable and Sustainable Energy Reviews, 224, p. 116035. doi: 10.1016/j.rser.2025.116035.

[7] Eastman, J. A., Choi, U. S., Li, S., Thompson, L. J., and Lee, S., 1996. Enhanced thermal conductivity through the development of nanofluids. MRS Online Proceedings Library, 457, p. 3. doi: 10.1557/PROC-457-3.

[8] Sarkar, J., Ghosh, P., and Adil, A., 2015. A review on hybrid nanofluids: Recent research, development and applications. Renewable and Sustainable Energy Reviews, 43, pp. 164-177. doi: 10.1016/j.rser.2014.11.023.

[9] Ranga Babu, J. A., Kumar, K. K., and Srinivasa Rao, S., 2017. State-of-art review on hybrid nanofluids. Renewable and Sustainable Energy Reviews, 77, pp. 551-565. doi: 10.1016/j.rser.2017.04.040.

[10] Sidik, N. A. C., Adamu, I. M., Jamil, M. M., Kefayati, G. H. R., Mamat, R., and Najafi, G., 2016. Recent progress on hybrid nanofluids in heat transfer applications: A comprehensive review. International Communications in Heat and Mass Transfer, 78, pp. 68-79. doi: 10.1016/j.icheatmasstransfer.2016.08.019.

[11] Evne, S.K., Kumar, A., Ahirwar, B.K., 2024 Experimental investigation of heat transfer enhancement through free single jet impingement using TiO₂-water nanofluid. Journal of Thermal Analysis and Calorimetry, 149, pp. 9921–9936. doi: 10.1007/s10973-024-13390-3.

[12] Chourasia, S., Kumar, A., and Ahirwar, B. K., 2024. Numerical study of fluid flow and heat transfer in a circular tube with Trapezoidal-cut twisted tape inserts. Journal of Thermal Analysis and Calorimetry, 149(17), pp. 9851-9866. doi: 10.1007/s10973-024-13389-w.

[13] Xuan, Y., and Li, Q., 2000. Heat transfer enhancement of nanofluids. International Journal of Heat and Fluid Flow, 21(1), pp. 58-64. doi: 10.1016/S0142-727X(99)00067-3.

[14] Adio, S. A., Atofarati, E. O., Muritala, A. O., Huan, Z., and Veeredhi, V. R., 2025. Nanofluids flow boiling and convective heat transfer in microchannels: A systematic review and bibliometrics analysis. Journal of Thermal Analysis and Calorimetry, 150(12), pp.8879-8911. doi: 10.1007/s10973-025-14265-x.

[15] Ratul, R. E., Ahmed, F., Alam, S., Karim, M. R., and Bhuiyan, A. A., 2023. Numerical study of turbulent flow and heat transfer in a novel design of serpentine channel coupled with D-shaped jaggedness using hybrid nanofluid. Alexandria Engineering Journal, 68, pp. 647-663. doi: 10.1016/j.aej.2023.01.061.

[16] Ahmed, F., Abir, M. A., Redwan, A. S. M., Bhuiyan, A. A., and Mollah, A. S., 2021. The impact of D-shaped jaggedness on heat transfer enhancement technique using Al₂O₃ based nanoparticles. International Journal of Thermofluids, 10, p. 100069. doi: 10.1016/j.ijft.2021.100069.

[17] Yu, W., and Xie, H., 2012. A review on nanofluids: Preparation, stability mechanisms, and applications. Journal of Nanomaterials, 2012, Article ID 435873. doi: 10.1155/2012/435873.

[18] Shah, R. K., and Sekulic, D. P., 2003. Fundamentals of Heat Exchanger Design. John Wiley & Sons.

[19] Kakaç, S., Liu, H., and Pramuanjaroenkij, A., 2002. Heat Exchangers: Selection, Rating, and Thermal Design. 2nd ed. Boca Raton: CRC Press. doi: 10.1201/9781420053746.

[20] Ahirwar, B.K., and Kumar, A., 2024. Experimental study of thermal performance factor for double-pipe heat exchanger using ZnO-water nanofluid. Journal of Thermal Analysis and Calorimetry, 149(15), pp. 8345-8364. doi: 10.1007/s10973-024-13118-3.

[21] Ahirwar, B.K., and Kumar, A., 2024. Effect of wire coil inserts on heat transfer enhancement and fluid flow characteristics of a double-pipe heat exchanger. Journal of Thermal Analysis and Calorimetry, 149, pp. pages 3027–3042. doi: 10.1007/s10973-024-12889-z.

[22] Suresh, S., Venkitaraj, K. P., Selvakumar, P., and Chandrasekar, M., 2011. Synthesis of Al₂O₃-Cu/water hybrid nanofluids using two step method and its thermo physical properties. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 388(1), pp. 41-48. doi: 10.1016/j.colsurfa.2011.08.005.

[23] Madhesh, D., Parameshwaran, R., and Kalaiselvam, S., 2014. Experimental investigation on convective heat transfer and rheological characteristics of Cu-TiO₂ hybrid nanofluids. Experimental Thermal and Fluid Science, 52, pp. 104-115. doi: 10.1016/j.expthermflusci.2013.08.026.

[24] Hamid, K. A., Azmi, W. H., Nabil, M. F., Mamat, R., and Sharma, K. V., 2018. Experimental investigation of thermal conductivity and dynamic viscosity on nanoparticle mixture ratios of TiO₂-SiO₂ nanofluids. International Journal of Heat and Mass Transfer, 116, pp. 1143-1152. doi: 10.1016/j.ijheatmasstransfer.2017.09.087.

[25] Zarringhalam, M., Karimipour, A., and Toghraie, D., 2016. Experimental study of the effect of solid volume fraction and Reynolds number on heat transfer coefficient and pressure drop of CuO-Water nanofluid. Experimental Thermal and Fluid Science, 76, pp. 342-351. doi: 10.1016/j.expthermflusci.2016.03.026.

[26] Moghadassi, A., Ghomi, E., and Parvizian, F., 2015. A numerical study of water based Al₂O₃ and Al₂O₃-Cu hybrid nanofluid effect on forced convective heat transfer. International Journal of Thermal Sciences, 92, pp. 50-57. doi: 10.1016/j.ijthermalsci.2015.01.025.

[27] Ali, F. A., and Alsaffawi, A. M., 2023. Friction Factor and Heat Transfer Enhancement of Hybrid Nanofluids in a Heated Circular Tube. International Journal of Heat and Technology, 41(5), pp. 1383-1388. doi: 10.18280/ijht.410530.

[28] Yassien, H. N. S., Abedalh, A. S., Yousif, O. M., and Hussein, A. T., 2025. Impact of CuO+H2O nanofluid on the cooling towers performance with varying packing densities. Results in Engineering, 26, p. 104664. doi: 10.1016/j.rineng.2025.104664.

[29] Abdallah, A. S., Yasin, N. J., and Ameen, H. A., 2024. A numerical investigation on the effect of nano metal oxide coating fins on the thermal performance of heat pipe heat exchanger. AIP Conference Proceedings. doi: 10.1063/5.0212235.

[30] Shaalan, Z. A., Abedalh, A. S., and Hamadalla, M. W., 2021. Heat pump performance enhancement by using a nanofluids (experimental study). Journal of Mechanical Engineering Research and Developments, 44(2), pp. 1-9.

[31] Chun, B.H., Kang, H.U., and Kim, S.H., 2008. Effect of alumina nanoparticles in the fluid on heat transfer in double-pipe heat exchanger system. Korean Journal of Chemical Engineering, 25, pp. 966–971. doi: 10.1007/s11814-008-0156-5.

[32] Ding, Y., Alias, H., Wen, D., and Williams, R. A., 2006. Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids). International Journal of Heat and Mass Transfer, 49(1), pp. 240-250. doi: 10.1016/j.ijheatmasstransfer.2005.07.009.

[33] Abdallah, A., Yasin, N., and Ameen, H., 2022. Thermal performance enhancement of heat pipe heat exchanger in the air-conditioning system by using nanofluid. Frontiers in Heat and Mass Transfer, 18, pp. 1-7. doi: 10.5098/hmt.18.10.

[34] Yasin, N. J., Jehhef, K. A., and Abedalh, A. S., 2019. Experimental and theoretical study of heat pump performance enhancement by using a nanorefrigerants. Technology, 10(1), pp. 25-42. doi: 10.34218/IJMET.10.1.2019.003.

[35] Abedalh, A. S., Hussein, A. T., and Yousif, A. A., 2023. Experimental investigation for vapor compression system performance enhancement through condenser cooling by using shallow fluidized bed. Journal of Thermal Analysis and Calorimetry, 148(21), pp. 12301-12310. doi: 10.1007/s10973-023-12495-5.

[36] Kline, S.J., and McClintock, F.A., 1963. Describing uncertainties in single-sample experiments. Mechanical Engineering, 75, pp. 3-8.