Heat Transfer Enhancement of Crossflow Air-to-Water Fin-and-Tube Heat Exchanger by Using Delta-Winglet Type Vortex Generators
Abstract
:1. Introduction
2. Mathematical Modelling
2.1. Problem Description and Computational Domain
2.2. Governing Equations
2.3. Boundary Conditions
3. Numerical Method
- Change in standard deviation of velocity profiles between inlet and outlet water boundaries is less than 0.1%;
- Change in minimum and maximum velocity values between inlet and outlet water boundaries is less than 0.1%;
- Change in air outlet temperature between two separate simulations is less than 0.002 °C.
4. Experimental Validation
4.1. Experimentally Studied Fin-and-Tube Heat Exchanger and Test Line
4.2. Test Conditions
4.3. Model Validation
5. Results and Discussion
5.1. Comparison of Air-Side Colburn Factors j and Friction Factors f
5.2. Distributions of Temperatures, Velocities and Air-Side Heat Transfer Coefficients
5.3. Comparison of the Air-Side Thermal-Hydraulic Performances
5.4. Comparison of the Overall Heat Transfer Coefficients and Air-Side Thermal Resistance Fractions
6. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Nomenclature
A | cross-sectional area (m2) |
Ao | total outside surface area of the finned tube (m2) |
Amin | minimal flow cross-sectional area (m2) |
C | heat capacity rate (W/K) |
C* | Cmin/Cmax heat capacity rate ratio |
c | specific heat capacity (J/kgK) |
Dh | 4∙Amin∙Lx/Ao, hydraulic diameter (m) |
d | tube diameter (m) |
Fp | fin pitch (m) |
f | friction factor |
Hvg | height of vortex generator (m) |
h | heat transfer coefficient (W/m2K) |
j | Colburn factor |
k | turbulence kinetic energy (m2/s2) |
Lx | fin length (m) |
Lvg | length of vortex generator (m) |
Lz | tube length (m) |
mass flow rate (kg/s) | |
Nt | number of tubes |
p | pressure (Pa) |
Pr | Prandtl number |
specific heat flux (W/m2) | |
exchanged heat flux (W) | |
R | thermal resistance (K/W) |
ReDh | ρDhwc/μ, Reynolds number based on hydraulic diameter |
Redi | ρdiw/μ, Reynolds number based on inner tube diameter |
r | tube radius (m) |
T | temperature (K) |
TPF | thermal performance factor |
U | overall heat transfer coefficient (W/m2K) |
wc | centreline velocity (m/s) |
wcore | velocity at minimal flow cross-sectional area (m/s) |
wx, wy, wz | velocity components in x, y, and z-directions (m/s) |
x, y, z | Cartesian coordinates (m) |
XL | longitudinal tube pitch (m) |
XT | transverse tube pitch (m) |
y+ | ∆ynρ(τwallρ)0.5/μ dimensionless distance from the wall |
Greek symbols | |
α | attack angle (°) |
δ | thickness (m) |
∆p | pressure drop (Pa) |
∆T | temperature difference (K) |
∆x | distance between tube and winglet in airflow direction (m) |
∆y | distance between tube and winglet in spanwise direction (m) |
∆yn | distance of the near-wall node to the solid surface (m) |
ηf | fin efficiency |
ηo | overall surface efficiency |
λ | thermal conductivity (W/mK) |
μ | dynamic viscosity (Pa∙s) |
ρ | density (kg/m3) |
σk | turbulent Prandtl number for kinetic energy |
σω | turbulent Prandtl number for energy dissipation rate |
τwall | wall shear stress (kg/s2m) |
ω | turbulence frequency (1/s) |
Subscripts | |
air | air side |
avg | average |
DWD | delta-winglet downstream |
DWU | delta-winglet upstream |
f | fin |
i | tube side |
in | inlet |
LMTD | logarithmic mean temperature difference |
min | minimum value |
max | maximum value |
o | total outside surface |
out | outlet |
red | reduced |
ref | baseline case |
vg | vortex generator |
water | water side |
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Batista, J.; Trp, A.; Lenic, K. Heat Transfer Enhancement of Crossflow Air-to-Water Fin-and-Tube Heat Exchanger by Using Delta-Winglet Type Vortex Generators. Energies 2022, 15, 2070. https://doi.org/10.3390/en15062070
Batista J, Trp A, Lenic K. Heat Transfer Enhancement of Crossflow Air-to-Water Fin-and-Tube Heat Exchanger by Using Delta-Winglet Type Vortex Generators. Energies. 2022; 15(6):2070. https://doi.org/10.3390/en15062070
Chicago/Turabian StyleBatista, Josip, Anica Trp, and Kristian Lenic. 2022. "Heat Transfer Enhancement of Crossflow Air-to-Water Fin-and-Tube Heat Exchanger by Using Delta-Winglet Type Vortex Generators" Energies 15, no. 6: 2070. https://doi.org/10.3390/en15062070