Heiles Open Fin Channel


Flow Simulator uses a variety of heat transfer correlations to model the heat exchange phenomenon in flow and thermal networks. The correlation types available in Flow Simulator for modeling convection through Fin Channels are discussed below.

Convection through Fin Channels

(i) Heiles Open Fin Channel (Forced Convection)
Used to model heat exchange between fin channels and the free stream fluid through Forced Convection.
Turbulent Duct NU
Heiles Open Fin Channel
Table 1. Inputs List
Index UI Name (.flo label) Description Mandatory/Not Mandatory
1 Flow chamber (Flow_Cham) The flow chamber ID which represents the chamber in the channel flow path.

On specifying a valid chamber ID, quantities such as fluid velocity, mass flow rate, and so on, that are necessary for computation are automatically retrieved.


In AUTO mode, the solver automatically identifies the chamber that is connected to the convector and would retrieve Fluid Velocity values from there.

You can also clear the AUTO mode and pick a specific chamber to get the velocity from.

If you want to use a fixed velocity value for the correlation, this input can be left as 0, and fluid velocity can be entered manually by clearing the Fluid Velocity AUTO option.

2 Fluid Velocity (FLOW_VEL) Velocity of the fluid in the channel.

In AUTO mode, if a valid flow chamber ID is provided, then the fluid velocity is automatically retrieved.


If a non-zero Flow Chamber input is provided (either AUTO or a valid chamber ID), and the Fluid Velocity is also set to AUTO, then the solver uses the fluid velocity retrieved from those chambers.

If the Flow chamber input is zero, then you must clear the fluid velocity AUTO option and provide a valid velocity value to be used in the correlation.

3 Axial length of fin (FIN_LENGTH) Length of the fins in the fin channel. Mandatory
  Height of fin (FIN_HEIGHT) Height of the fins in the fin channel. Mandatory
4 Spacing between fins (FIN_SPACE) Spacing between the two fins. Mandatory
5 Thickness of fins (FIN_THK) Thickness of fins in the fin channel. Mandatory
6 Number of fins (NUM_FINS) Total number of fins. Mandatory
7 Turbulence Factor (TURB_FAC) A multiplier used in the Heiles Open Fin Channel correlation. Not Mandatory

Default is AUTO.

Default (AUTO) value is 1.8, as per reference 1.

8 HTC Multiplier (HTC_MULT) A constant multiplier to scale the value of the heat transfer coefficient obtained from the correlation. Not Mandatory

Default value is 1.0.


The expression of heat transfer coefficient for a fin channel of axial length L and spacing S, subjected to Forced Convection, is given by (Ref. 1), often referred to as Heiles Open Fin Channel Forced Convection:

Figure 1.

Figure 2.


L = Axial length of the fin channel.

D = Hydraulic diameter of the fin channel (4xChannel Area/Channel Perimeter, including the open side).

ν = fluid velocity.

ρ = Density of the fluid at the film temperature (TFluid-Stream + TWall / 2).

Cp = Specific heat of the fluid at the film temperature.
Table 2. Output List
Index .flo label Description
1 TNET Thermal network ID, which has the convector where this correlations is used.
2 CONV_ID Convector ID, which is using this correlation.
3 FLOW_CHM User-defined flow chamber or retrieved under the AUTO mode.
4 FLOW_VEL User-defined flow velocity or calculated by the solver under the AUTO mode.
5 FIN_LEN User-defined fin length.
6 FIN_HGHT User-defined fin height.
7 FIN_SPCE User-defined spacing between two fins.
8 FIN_THK User-defined thickness of fins.
9 CHNL_HYDDIA Channel hydraulic diameter as calculated by the solver.
10 CHNL_PERIM Channel perimeter as calculated by the solver.
11 CHNL_AREA Channel area as calculated by the solver.
12 TOT_AREA Total area of heat transfer.
13 CHNL_RE Channel Reynolds number as calculated by the solver.
12 HTC Heat transfer coefficient calculated as the correlation.

Heat Transfer Correlation References

  1. Staton, David A., and Andrea Cavagnino. "Convection heat transfer and flow calculations suitable for electric machines thermal models." IEEE transactions on industrial electronics 55, no. 10 (2008): 3509-3516.
  2. Van De Pol, D. W., and J. K. Tierney, "Free convection Nusselt number for vertical U-shaped channels, J. Heat Transfer. Nov 1973, 95(4): 542-543.
  3. Jones, Charles D., and Lester F. Smith. "Optimum arrangement of rectangular fins on horizontal surfaces for free-convection heat transfer.", J. Heat Transfer. Feb 1970, 92(1): 6-10.