Channel-to-Pin and Channel-to-Duct Heat Transfer Modeling

The pin surface temperature are computed via the convective heat transfer coefficient as follows:

where:

• is the surface temperature for the pin at a height

• is the number of subchannels neighboring the pin

• is the bulk temperature for a subchannel neighboring the pin at a height

• is the linear heat generation rate for the pin at a height

• is the pin diameter at a height

• is the convective heat transfer coefficient for the subchannel next to the duct node at a height

For the duct, the duct surface temperature is defined as follows:

where:

• is the duct surface temperature at a height

• is the bulk temperature of the subchannel next to the duct node

• is the heat flux at the duct at a height

• is the convective heat transfer coefficientfor the subchannel next to the duct node at a height

In both cases, the convective heat transfer coefficients are computed using the Nusselt number (Nu) as follows:

where:

• is the local thermal conductivity of the fluid in the subchannel neighboring the structure

• is the hydraulics diameter of the subchannel neighboring the structure

The modeling of the Nusselt number and consequently of the convective heat transfer coefficient h is selected by the user through a closure. The closure models available to the user that are implemented in SCM are the following:

• Dittus-Boelter (recommended for water coolant)

• Modified Gnielinski (recommended for duct surface)

• Kazimi-Carelli (applicable to liquid metals)

• Schad-Modified (applicable to liquid metals)

• Graber-Rieger (applicable to liquid metals)

• Borishanskii (applicable to liquid metals)

All these models inherit from the base class: SCMHTCClosureBase. A synopsis of the closure models availabe in SCM with the range of validity, is presented in Table HTC models.