https://orcid.org/0000-0002-2209-9617
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ABSTRACT
Turbulators have been developed as a capable passive technique for enhancing heat transfer through channels. The shape and arrangement of these geometries are the main factors in their performance. In the current analysis, three curved turbulators, i.e. circular (C), rectangular (R), and diamond (D), with four various arrangements, i.e. forward-vertical (FV), forward-horizontal (FH), backward-vertical (BV), and backward-horizontal (BH), inside a rectangular channel at the constant heat flux are examined. The thermal and aerodynamic characteristics are analyzed using the dimensional parameters of h and ∆p as well as the dimensionless parameters of Nuenh/Nusmo vs. fenh/fsmo. Based on experimental data and their corresponding numerical results, the effects of both shape and arrangement on streamlines and contours of airflow are discussed. Also, a performance index (η) is applied to apprise overall thermal-aerodynamic performance at inlet velocities of 1, 2, and 3 m/s. The results show that the value of η has a deceasing trend with the inlet velocity, indicating a better performance is found at lower velocity for these turbulators. The best performance could be achieved by the C turbulators at the FV arrangement (CFV model with η between 1.36 and 1.52), followed the DFH model with η between 1.35 and 1.49.
Acknowledgments
The authors thank Mr. M.R. Vahedian for assistance with the test setup assembly. This work is supported by Islamic Azad University of Shahrood Branch and Ferdowsi University of Mashhad.
Declaration of competing interest
The authors declared that there is no conflict of interest.
Nomenclature
| Ac | = | frontal flow area (m2) |
| At | = | total heat transfer area (m2) |
| cp | = | specific heat (J kg−1 K−1) |
| Dh | = | hydraulic diameter (m) |
| h | = | heat transfer coefficient (W m−2 K−1) |
| k | = | thermal conductivity (W m−1 K−1) |
| L | = | channel length, (m) |
| Q | = | heat transfer rate (W) |
| p | = | pressure (Pa) |
| ∆p | = | pressure drop (Pa) |
| T | = | temperature (K) |
| v | = | velocity (m s−1) |
| x, y, z | = | coordinates |
Greek Symbol
| ρ | = | density (kg m−3) |
| μ | = | dynamic viscosity (Pa s) |
| η | = | performance index |
Subscripts
| enh | = | enhanced |
| in | = | inlet |
| m | = | mean |
| out | = | outlet |
| smo | = | smooth |
| w | = | wall |
Dimensionless groups
| f | = | Friction factor |
| Nu | = | Nusselt number |
| Pr | = | Prandtl number |
| Re | = | Reynolds number |
Acronyms
| B | = | Backward |
| C | = | Circular |
| D | = | Diamond |
| F | = | Forward |
| H | = | Horizontal |
| R | = | Rectangular |
| V | = | Vertical |
Correction Statement
This article has been republished with minor changes. These changes do not impact the academic content of the article.