Fin Channel
Description
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.
 (i) Fin Channel Free Convection (Natural Convection)
 Used to model heat exchange between fin channels and the free stream fluid through Natural Convection.
 Type
 Free Convection NU
 Subtype
 Fin Channel Free Convection
Index  UI Name (.flo label)  Description  Mandatory/Not Mandatory 

1  Channel Orientation (ORIENT)  Orientation of the channels. There are two options:

Mandatory Based on the channel orientation, the correlation for HTC changes. Refer to the Formulation section for more details. 
2  Axial Length of fin (LENGTH))  Length of the fins in the fin channel.  Mandatory 
3  Height of fin (HEIGHT)  Height of the fins in the fin channel.  Mandatory 
4  Spacing between fins (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 (Number)  Total number of fins.  Mandatory 
7  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. 
Formulation
L = Axial length of the fin.
H = Height of the fin.
S = Spacing between two fins.
r = Characteristic length, Fin hydraulic radius (2LS / 2L+S).
α = Channel Aspect Ratio (S/L).
For Spacing > 2 in, the correlation is given by (Ref. 3):
Where,
S = Characteristic length (spacing between the fins).
Gr = Grashoff number based on the characteristic length (S).
Pr = Prandtl number at film temperature (T_{FluidStream} + T_{Wall} / 2).
The heat transfer coefficient from Nusselt number is obtained as:
Where, k = Thermal conductivity of the fluid at film temperature (T_{FluidStream} + T_{Wall} / 2).
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  ORIENTATION  Userdefined motor orientation. 
4  FIN_LEN  Userdefined fin length. 
5  FIN_HGHT  Userdefined fin height. 
6  FIN_SPCE  Userdefined spacing between two fins. 
7  FLOW_VEL  Fluid velocity calculated/autoretrieved for the model. 
8  CHRTSC_LENGTH  Characteristic length used in the computation of HTC. 
9  TOT_AREA  Total fin channel area for convection. 
10  CHNL_GR  Channel Grashoff number. 
11  CHNL_PR  Channel Prandtl number. 
12  HTC  Heat transfer coefficient calculated as per the correlation. 
Heat Transfer Correlation References
 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): 35093516.
 Van De Pol, D. W., and J. K. Tierney, "Free convection Nusselt number for vertical Ushaped channels, J. Heat Transfer. Nov 1973, 95(4): 542543.
 Jones, Charles D., and Lester F. Smith. "Optimum arrangement of rectangular fins on horizontal surfaces for freeconvection heat transfer.", J. Heat Transfer. Feb 1970, 92(1): 610.