Abstract
This study applies a three-dimensional computational fluid dynamics commercial software in conjunction with various flow models to estimate the heat transfer and fluid flow characteristics of the two-row plate-finned tube heat exchanger in staggered arrangement. The effect of air speed and fin spacing on the results obtained is investigated. Temperature and velocity distributions of air between the two fins and heat transfer coefficient on the fins are determined using the laminar flow and RNG k-ε turbulence models. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. Furthermore, the fin temperature measured at the selected locations also coincides with the experimental temperature data. The results obtained using the RNG k-ε turbulence model are more accurate than those using the laminar flow model. An interesting finding is the number of grid points may also need to change with fin spacing and air speed.
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Abbreviations
- Af :
-
Lateral surface area of fin (m2)
- Aj :
-
Area of the jth sub-fin region (m2)
- cμ, c1ε, c2ε :
-
Coefficients in turbulent model, 0.0845, 1.42, 1.68
- cp :
-
Specific heat (J/kg-K)
- Dh :
-
Hydraulic diameter (m)
- d0 :
-
Outer diameter of the circular tube (m)
- gj :
-
Gravitational acceleration in xj direction (m/s2)
- Gb :
-
Production of turbulent kinetic energy due to buoyancy, \({\text{G}}_{\text{b}} =\upbeta{\text{g}}_{\text{j}} \frac{{\upmu_{\text{t}} }}{{\Pr_{\text{t}} }}\frac{{\partial {\text{T}}_{\text{a}} }}{{\partial {\text{x}}_{\text{j}} }}\)
- Gk :
-
Production of turbulent kinetic energy due to the velocity gradient, Gk = μtS2
- h:
-
Local heat transfer coefficient (W/m2-K)
- \({\bar{\text{h}}}\) :
-
Average heat transfer coefficient on the fin (W/m2-K)
- \({\bar{\text{h}}}_{ 0}\) :
-
Heat transfer coefficient under the situation of \({\bar{\text{T}}}_{\text{o}}\) (W/m2-K)
- \({\bar{\text{h}}}_{\text{j}}\) :
-
Heat transfer coefficient in the j-th sub-fin region (W/m2-K)
- k:
-
Turbulent kinetic energy
- kf :
-
Thermal conductivity of fin (W/m-K)
- ka :
-
Thermal conductivity of air (W/m-K)
- L:
-
Length and width of the square fin (m)
- N:
-
Number of sub-fin regions
- Ntf :
-
Number of grid points on the lateral surface
- p:
-
Pressure
- Pr:
-
Prandtl number
- Prt :
-
Turbulent Prandtl number, 0.85
- Q:
-
Total heat rate dissipated from the entire fin (W)
- Qj :
-
Heat rate dissipated from the jth sub-fin region (W)
- s:
-
Fin spacing (mm)
- S:
-
(2 Sij Sij)1/2
- Si :
-
Outer boundary surface of the ith circular tube
- Sij :
-
Mean strain rate tensor, (\(\partial\) ui/ \(\partial\) xj + \(\partial\) uj/ \(\partial\) xi)/2
- T:
-
Fin temperature (K)
- Ta :
-
Air temperature (K)
- Tj :
-
Measured fin temperature at the jth measurement location (K)
- To,i :
-
Outer surface temperature of the ith circular tube (K)
- \({\bar{\text{T}}}_{\text{o}}\) :
-
Average temperature of the four tubes (K)
- T∞ :
-
Ambient air temperature (K)
- t:
-
Fin thickness (m)
- ui :
-
Velocity component in xi direction (m/s)
- Vair :
-
Frontal air velocity (m/s)
- x, y, z:
-
Cartesian coordinates (m)
- xi :
-
Index notation of Cartesian coordinates (m)
- αε :
-
Parameter in Eq. (15)
- αp :
-
Parameter in Eq. (10)
- β:
-
Volumetric thermal expansion coefficient
- βt :
-
Parameter in RNG k-ε model, 0.012
- δij, δj2 :
-
Kronecker delta function
- ε:
-
Viscous dissipation rate of turbulence kinetic energy
- η:
-
Ratio of characteristic time scales of turbulence and the mean flow fields, η = Sk/ε
- η0 :
-
Parameter, 4.38
- μeff :
-
Total dynamic viscosity, ρνeff = ρν + μt
- μt :
-
Eddy viscosity, cμρk2/ε
- ν:
-
Laminar kinematic viscosity (kg/s-m)
- νeff :
-
Effective kinematic viscosity, μeff/ρ (kg/s-m)
- νt :
-
Turbulent kinematic viscosity, μt/ρ (kg/s-m)
- \(\uprho\) :
-
Air density (kg-m3)
- σk, σε :
-
Turbulent Prandtl numbers for diffusion of k and ε, 1.393, 1.393
References
Sparrow EM, Samie F (1985) Heat transfer and pressure drop for one- and two-row arrays of finned tubes. Int J Heat Mass Transf 28:2247–2259
Rosman EC, Carajilescov P, Saboya FEM (1984) Performance of one- and two-row tube and plate fin heat exchangers. ASME J Heat Transf 106:627–632
Rocha LAO, Saboya FEM, Vargas JVC (1997) A comparative study of elliptical and circular sections in one- and two-row tubes and plate fin heat exchangers. Int J Heat Fluid Flow 18:247–252
Saboya SM, Saboya FEM (2001) Experiments on elliptic sections in one- and two-row arrangements of plate fin and tube heat exchange. Exp Therm Fluid Sci 24:67–75
Huang CH, Yuan IC, Ay H (2003) A three-dimensional inverse problem in imaging the local heat transfer coefficients for plate finned-tube heat exchangers. Int J Heat Mass Transf 46:3629–3638
Huang CH, Yuan IC, Ay H (2009) An experimental study in determining the local heat transfer coefficients for the plate finned-tube heat exchangers. Int J Heat Mass Transfer 52:4883–4893
Chen HT, Chou JC, Wang HC (2007) Estimation of heat transfer coefficient on the vertical plate fin of finned-tube heat exchangers for various air speeds and fin spacings. Int J Heat Mass Transf 50:45–57
Chen HT, Hsu WL (2008) Estimation of heat-transfer characteristics on a vertical annular circular fin of finned-tube heat exchangers in forced convection. Int J Heat Mass Transf 51:1920–1932
Chen HT, Lai JR (2012) Study of heat-transfer characteristics on the fin of two-row plate finned-tube heat exchangers. Int J Heat Mass Transf 50:45–57
Hu X, Jacobi AM (1993) Local heat transfer behavior and its impact on a single-row, annularly finned tube heat exchanger. ASME J Heat Transf 115:66–74
Watel B, Harmand S, Desmet B (1999) Influence of flow velocity and fin spacing on the forced convective heat transfer from an annular-finned tube. JSME Int J, Ser B 42(1):56–64
Mon MS, Gross U (2004) Numerical study of fin-spacing effects in annular-finned tube heat exchangers. Int J Heat Mass Transf 47:1953–1964
FLUENT Dynamics Software (2010) FLUENT, Lehanon, NH-USA
Bilirgen H, Dunbar S, Levy EK (2013) Numerical modeling of finned heat exchangers. Appl Therm Eng 61:278–288
Gherasim I, Galanis N, Nguyen CT (2011) Heat transfer and fluid flow in a plate heat exchanger. Part II: assessment of laminar and two-equation turbulent models. Int J Therm Sci 50:1499–1511
Jang JY, Wu MC, Chang WJ (1996) Numerical and experimental studies of three-dimensional platefin-and-tube heat exchangers. Int J Heat Mass Transf 39:3057–3066
Jang JY, Chen LK (1997) Numerical analysis of heat transfer and fluid flow in a three-dimensional wavy-fin and tube heat exchanger. Int J Heat Mass Transf 40:3981–3990
Tutar M, Akkoca A (2004) Numerical analysis of fluid flow and heat transfer characteristics in three-dimensional plate fin-and tube heat exchangers. Numer Heat Transf A 46:301–321
Sheu TWH, Tsai SF, Chiang TP (1999) Numerical study of heat transfer in two-row heat exchangers having extended fin surfaces. Numer Heat Transf A 35:797–814
Xie GN, Wang QW, Sunden B (2009) Parametric study and multiple correlations on air-side heat transfer and friction characteristics of fin-and-tube heat exchangers with large number of large-diameter tube rows. Appl Therm Eng 29:1–16
Lai JR (2011) Study of heat-transfer characteristics on the fin of four-tube plate finned-tube heat exchangers. Department of Mechanical Engineering thesis, National Cheng Kung University, Taiwan
Velayati E, Yaghoubi M (2005) Numerical study of convective heat transfer from an array of parallel bluff plates. Int J Heat Fluid Flow 26:80–91
Kasagi N (1992) Direct numerical simulation data bases: An effective tool in fundamental studies of turbulent heat transfer. In: Nakayama W, Yang KT (eds) Computers and computing in heat transfer science and engineering. CRC Press, Boca Raton, pp 97–117
Acknowledgments
The authors gratefully acknowledge the financial support provided by the National Science Council of the Republic of China under Grant No. NSC 98-2221-E-006-177-MY3 and NSC 102-2221-E-006-177-MY3. We would also like to thank Professor Chin-Hsiang Cheng at National Cheng Kung University for providing us access to the computational fluid dynamics software FLUENT.
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Chen, HT., Lu, CH., Huang, YS. et al. Numerical estimation of heat transfer characteristics for two-row plate-finned tube heat exchangers with experimental data. Heat Mass Transfer 52, 969–979 (2016). https://doi.org/10.1007/s00231-015-1612-5
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DOI: https://doi.org/10.1007/s00231-015-1612-5