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13.4.3 Steps in Using Periodic Heat Transfer

A typical calculation involving both streamwise-periodic flow and periodic heat transfer is performed in two parts. First, the periodic velocity field is calculated (to convergence) without consideration of the temperature field. Next, the velocity field is frozen and the resulting temperature field is calculated. These periodic flow calculations are accomplished using the following procedure:

1.   Set up a grid with translationally periodic boundary conditions.

2.   Input constant thermodynamic and molecular transport properties.

3.   Specify either the periodic pressure gradient or the net mass flow rate through the periodic boundaries.

4.   Compute the periodic flow field, solving momentum, continuity, and (optionally) turbulence equations.

5.   Specify the thermal boundary conditions at walls as either heat flux or constant temperature.

6.   Define an inlet bulk temperature.

7.   Solve the energy equation (only) to predict the periodic temperature field.

These steps are detailed below.

In order to model the periodic heat transfer, you will need to set up your periodic model in the manner described in Section  9.4.3 for periodic flow models with the pressure-based solver, noting the restrictions discussed in Sections  9.4.1 and 13.4.1. In addition, you will need to provide the following inputs related to the heat transfer model:

1.   Activate solution of the energy equation in the Energy panel.

Define $\rightarrow$ Models $\rightarrow$ Energy...

2.   Define the thermal boundary conditions according to one of the following procedures:

Define $\rightarrow$ Boundary Conditions...

  • If you are modeling periodic heat transfer with specified-temperature boundary conditions, set the wall temperature $T_{\rm wall}$ for all wall boundaries in their respective Wall panels. Note that all wall boundaries must be assigned the same temperature and that the entire domain (except the periodic boundaries) must be "enclosed'' by this fixed-temperature condition, or by symmetry or adiabatic ( $q$=0) boundaries.

  • If you are modeling periodic heat transfer with specified-heat-flux boundary conditions, set the wall heat flux in the Wall panel for each wall boundary. You can define different values of heat flux on different wall boundaries, but you should have no other types of thermal boundary conditions active in the domain.

3.   Define solid regions, if appropriate, according to one of the following procedures:

Define $\rightarrow$ Boundary Conditions...

  • If you are modeling periodic heat transfer with specified-temperature conditions, conducting solid regions can be used within the domain, provided that on the perimeter of the domain they are enclosed by the fixed-temperature condition. Heat generation within the solid regions is not allowed when you are solving periodic heat transfer with fixed-temperature conditions.

  • If you are modeling periodic heat transfer with specified-heat-flux conditions, you can define conducting solid regions at any location within the domain, including volumetric heat addition within the solid, if desired.

4.   Set constant material properties (density, heat capacity, viscosity, thermal conductivity), not temperature-dependent properties, using the Materials panel.

Define $\rightarrow$ Materials...

5.   Specify the Upstream Bulk Temperature in the Periodic Conditions panel.

Define $\rightarrow$ Periodic Conditions...

figure   

If you are modeling periodic heat transfer with specified-temperature conditions, the bulk temperature should not be equal to the wall temperature, since this will give you the trivial solution of constant temperature everywhere.

6.   Set the solution parameters as described in Section  13.4.4

7.   Iterate the solution and monitor the convergence as described in Section  13.4.5.

8.   Postprocess the results as described in Section  13.4.6.


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