Abstract
In this study, steady-state forced convection heat transfer and pressure drop characteristics for hydrodynamically fully developed thermally developing three-dimensional turbulent flow in a horizontal smooth trapezoidal duct with corner angle of 75° and hydraulic diameter of 0.043 m were both experimentally and numerically investigated in the Reynolds number range from 2.6 × 103 to 67 × 103 for isothermal conditions. Results have shown that there is a good agreement between the present experimental and numerical results.
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Abbreviations
- A :
-
inner surface area (i.e. in contact with the air) of the trapezoidal cross-sectioned duct (m2)
- A c :
-
cross-sectional area of the trapezoidal duct (m2)
- C 1, C 2, C 3 :
- D h :
-
hydraulic diameter of the passageway through the considered trapezoidal duct (m)
- \( \mathop E\limits^{ \cdot } \) :
-
steady-state electric power supplied to heat the test section (W)
- f :
-
average Darcy friction factor (–)
- F :
-
view factor for thermal radiation from the duct ends to its surroundings (–)
- \( \overline{h} \) :
-
average heat transfer coefficient for the trapezoidal cross-sectioned duct’s inner surface and the forced air flow passing through the duct (W m−2 K−1)
- H :
-
height of the trapezoidal cross-section duct (m)
- k :
-
thermal conductivity of air (W m−1 K−1)
- L :
-
axial length of the test section (m)
- n 1, n 2, n 3 :
- Nu :
-
local Nusselt number (–)
- \( \overline{Nu} \) :
-
average Nusselt number for the steady state heat transfer between the test section’s inner surface and the air flow using D h (–)
- P :
-
wetted perimeter (m)
- ΔP :
-
pressure drop along the test section (Pa)
- Pr :
-
Prandtl number for the air flowing through the duct (–)
- \( \mathop {Q_{c} }\limits^{ \cdot } \) :
-
steady-state rate of convective heat transfer from the test section’s inner surface to the air flowing through the duct (W)
- \( \mathop {Q_{l} }\limits^{ \cdot } \) :
-
steady-state rate of heat loss by conduction from the test section to the ambient environment (W)
- \( \mathop {Q_{r} }\limits^{ \cdot } \) :
-
steady-state rate of thermal radiation from both ends of the test section to the surroundings (W)
- Re :
-
hydraulic diameter-based Reynolds number of the air flow (–)
- T b :
-
mean bulk temperature of the air flow in the duct (K)
- T bi, T bo :
-
mean bulk temperature of the air flow at the inlet and exit of the test section, respectively (K)
- T w :
-
surface temperature of the test section (K)
- T ∞ :
-
ambient temperature (K)
- T i :
-
inlet temperature (K)
- U :
-
mean velocity of the air flow in the trapezoidal duct (m s−1)
- \( {{\Updelta}}T_{\text{lm}} \) :
-
logarithmic mean temperature difference (K)
- x, y, z :
-
cartesian coordinates (–)
- Θ:
-
dimensionless temperature profile (–)
- ε :
-
emissivity (–)
- υ :
-
kinematic viscosity of air (m2 s−1)
- ρ :
-
density of the air (kg m−3)
- σ :
-
Stefan–Boltzmann constant (W m−2 K−4)
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Acknowledgments
The authors wish to thank the State Planning Organization for financial support of this project.
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Onur, N., Turgut, O., Arslan, K. et al. An experimental and three-dimensional numerical study on the convective heat transfer inside a trapezoidal duct under constant wall temperature. Heat Mass Transfer 45, 263–274 (2009). https://doi.org/10.1007/s00231-008-0423-3
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DOI: https://doi.org/10.1007/s00231-008-0423-3