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

Package Content

Name	Description
kc_flatTube
kc_roundTube

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

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.

Fuctions 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.

Extends from Modelica.Icons.Information (Icon for general information packages).

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

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.

Fuctions 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.

Extends from Modelica.Icons.Information (Icon for general information packages).