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Calculation of the mean convective heat transfer coefficient kc for the air-side heat transfer of heat exchangers with flat tubes and several fin geometries.
Functions kc_flatTube and kc_flatTube_KC
There are basically three differences:
-
The function kc_flatTube is using kc_flatTube_KC but offers additional output variables like e.g. Reynolds number or Nusselt number and failure status (an output of 1 means that the function is not valid for the inputs).
-
Generally the function kc_flatTube_KC is numerically best used for the calculation of the mean convective heat transfer coefficient kc at known mass flow rate.
-
You can perform an inverse calculation from kc_flatTube_KC, where an unknown mass flow rate is calculated out of a given mean convective heat transfer coefficient kc
Restriction
- According to the kind of fin geometry the calculation is valid in a range of Re from 100 to 5000.
- medium = air
Geometry
Calculation
The mean convective heat transfer coefficient kc for heat exchanger is calculated through the corresponding Coulburn factor j :
j = f(geometry, Re)
with the resulting mean convective heat transfer coefficient kc
kc = j * Re_L_p * Pr^(1/3) * lambda / L_p (Louver fin)
or
kc = j * Re_D_h * Pr^(1/3) * lambda / D_h (Rectangular offset strip fin)
with
| D_h | as hydraulic diameter [m], |
| kc | as mean convective heat transfer coefficient [W/(m2K)], |
| lambda | as heat conductivity of fluid [W/(mK)], |
| L_p | as louver pitch [m], |
| Nu_D_h = kc*D_h/lambda | as mean Nusselt number based on hydraulic diameter [-], |
| Nu_L_p = kc*L_p/lambda | as mean Nusselt number based on louver pitch [-], |
| Pr = eta*cp/lambda | as Prandtl number [-], |
| Re_D_h = rho*v*D_h/eta | as Reynolds number based on hydraulic diameter [-], |
| Re_L_p = rho*v*L_p/eta | as Reynolds number based on louver pitch [-], |
Verification
The mean Nusselt number Nu representing the mean convective heat transfer coefficient kc is shown below for different fin geometries at similar dimensions.
References
- Y.-J. CHANG and C.-C. WANG:
- A generalized heat transfer correlation for louver fin geometry.
In International Journal of Heat and Mass Transfer, volume 40, No. 3, pages 533-544, 1997.
- Y.-J. CHANG and C.-C. WANG:
- Air Side Performance of Brazed Aluminium Heat Exchangers.
In Journal of Enhanced Heat Transfer, volume 3, No. 1, pages 15-28, 1996.
- R.-M. Manglik, A.-E. Bergles:
- Heat Transfer and Pressure Drop Correlations for the Rectangular Offset Strip Fin Compact Heat Exchanger.
In Experimental Thermal and Fluid Science, volume 10, pages 171-180, 1995.
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Calculation of the mean convective heat transfer coefficient kc for the air-side heat transfer of heat exchangers with round tubes and several fin geometries.
Functions kc_roundTube and kc_roundTube_KC
There are basically three differences:
-
The function kc_roundTube is using kc_roundTube_KC but offers additional output variables like e.g. Reynolds number or Nusselt number and failure status (an output of 1 means that the function is not valid for the inputs).
-
Generally the function kc_roundTube_KC is numerically best used for the calculation of the mean convective heat transfer coefficient kc at known mass flow rate.
-
You can perform an inverse calculation from kc_roundTube_KC, where an unknown mass flow rate is calculated out of a given mean convective heat transfer coefficient kc
Restriction
- According to the kind of fin geometry the calculation is valid in a range of Re from 300 to 8000.
- medium = air
Geometry
Calculation
The mean convective heat transfer coefficient kc for heat exchanger is calculated through the corresponding Coulburn factor j :
j = f(geometry, Re)
with the resulting mean convective heat transfer coefficient kc
kc = j * Re * Pr^(1/3) * lambda / D_c
with
| D_c | as fin collar diameter [m], |
| kc | as mean convective heat transfer coefficient [W/(m2K)], |
| lambda | as heat conductivity of fluid [W/(mK)], |
| Nu = kc*D_c/lambda | as mean Nusselt number [-], |
| Pr = eta*cp/lambda | as Prandtl number [-], |
| Re = rho*v*D_c/eta | as Reynolds number [-], |
Verification
The mean Nusselt number Nu representing the mean convective heat transfer coefficient kc is shown below for different fin geometries at similar dimensions.
References
- C.-C. Wang, C.-T. Chang:
- Heat and mass transfer for plate fin-and-tube heat exchangers, with and without hydrophilic coating.
In International Journal of Heat and Mass Transfer, volume 41, pages 3109-3120, 1998.
- C.-C. Wang, C.-J. Lee, C.-T. Chang, S.-P. Lina:
- Heat transfer and friction correlation for compact louvered fin-and-tube heat exchangers.
In International Journal of Heat and Mass Transfer, volume 42, pages 1945-1956, 1999.
- C.-C. Wang, W.-H. Tao, C.-J. Chang:
- An investigation of the airside performance of the slit fin-and-tube heat exchangers.
In International Journal of Refrigeration, volume 22, pages 595-603, 1999.
- C.-C. Wang, W.-L. Fu, C.-T. Chang:
- Heat Transfer and Friction Characteristics of Typical Wavy Fin-and-Tube Heat Exchangers.
In Experimental Thermal and Fluid Science, volume 14, pages 174-186, 1997.
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