Experimental investigation of heat transfer enhancement using novel helical conical turbulators under turbulent airflow

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Polat M. N., KOCA T.

Journal of Thermal Analysis and Calorimetry, cilt.151, sa.8, ss.7157-7169, 2026 (SCI-Expanded, Scopus)

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 151 Sayı: 8
  • Basım Tarihi: 2026
  • Doi Numarası: 10.1007/s10973-026-15552-x
  • Dergi Adı: Journal of Thermal Analysis and Calorimetry
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Chimica, Compendex, Index Islamicus, INSPEC
  • Sayfa Sayıları: ss.7157-7169
  • Anahtar Kelimeler: Heat exchanger, Heat transfer, Hydraulic performance, Thermal performance, Turbulator
  • Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
  • İnönü Üniversitesi Adresli: Evet

Özet

In this study, the effects of novel helical twisted tape-type conical turbulators on heat transfer and pressure drop in a coaxial heat exchanger were experimentally investigated. The turbulators were designed with a specific taper angle (θ = 12°) and a maximum diameter of 72 mm to create a unique conical geometry. Turbulators with lengths of 200, 250, and 300 mm were arranged inside the tube in single, double, and triple configurations to induce flow turbulence. The influence of these turbulators on the Nusselt number and pressure drop was examined across a Reynolds number range of 4000–25000, and the contributions of various turbulator arrangements to system performance were comprehensively evaluated. To ensure the reliability of the study, experimental data from a plain tube were validated against results derived from the Gnielinski, Dittus–Boelter, Blasius, and Petukhov equations. Experimental results indicated an increase in the Nusselt number of up to 105.7% in the presence of turbulators compared to the plain tube. It was observed that both the Nusselt number and friction factor increased in correlation with the number of turbulators. The maximum thermal performance enhancement factor (PEC) was calculated as 1.108 at a Reynolds number of 20,000, while the minimum PEC was 0.66 at a Reynolds number of 4000. The maximum increase in the Nusselt number (Nua/Nu0) and friction factor (fa/f0) was determined to be 2.07 and 20, respectively. The highest heat transfer enhancement was achieved in experiments with three 300 mm long turbulators (C3), whereas the lowest enhancement was observed with a single 200 mm long turbulator (A1).