.Modelica.Fluid.Dissipation.Utilities.SharedDocumentation.HeatTransfer.HeatExchanger.kc_flatTube

Information

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

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.