Setting Boundary Conditions and Values

The thermal insulator consists of a closed heated box with two internal solid glass panels that are surrounded by air. The boundary specifications that are required for this analysis are wall thermal conditions and radiation properties at the boundaries.

A fixed heat flux of 1000 W/m2 is applied to the base of the box to provide the heat source. The top of the box is given a fixed temperature of 300 K which corresponds to the temperature of the environment. The vertical sides of the solid panels which are in contact with the environment are set to a fixed heat flux of -62.5 W/m2. All other wall boundary conditions are considered to be adiabatic, which is the default condition. Contact-type conducting boundaries are also used at solid-fluid interfaces.

You specify the radiation properties at the boundaries by assigning the relevant surface materials to the boundaries. The radiation properties of the solid-fluid interfaces are specified at the contact interface boundaries.

To set boundary conditions and values:
  1. To assign wall thermal conditions and boundary radiation properties to the fluid region, edit the Regions > Fluid > Boundaries node and set the following properties:
    Node Property Setting
    bottom-solid1 [Interface 2]
    Physics Values
    Surface Material Surface Material bottom-solid1
    bottom-solid2 [Interface 4]
    Physics Values
    Surface Material Surface Material bottom-solid2
    collector
    Physics Conditions
    Thermal Specification Condition Heat Flux
    Physics Values
    Heat Flux Value 1000 W/m2
    Surface Material Surface Material Collector
    side-1
    Physics Values
    Surface Material Surface Material Sides
    side-2
    Physics Values
    Surface Material Surface Material Sides
    side-3
    Physics Values
    Surface Material Surface Material Sides
    top
    Physics Conditions
    Thermal Specification Condition Temperature
    Physics Values
    Static Temperature Value 300 K
    Surface Material Surface Material Top
    top-solid1 [Interface 1]
    Physics Values
    Surface Material Surface Material top-solid1
    top-solid2 [Interface 3]
    Physics Values
    Surface Material Surface Material top-solid2
  2. To assign wall thermal conditions and boundary radiation properties to the solid region, edit the Regions > Solid > Boundaries node and set the following properties:
    Node Property Setting
    bottom-solid1 [Interface 2]
    Physics Values
    Surface Material Surface Material bottom-solid1
    bottom-solid2 [Interface 4]
    Physics Values
    Surface Material Surface Material bottom-solid2
    side-solid1
    Physics Conditions
    Thermal Specification Condition Heat Flux
    Physics Values
    Heat Flux Value -62.5 W/m2
    Surface Material Surface Material side-solid
    top-solid1 [Interface 1]
    Physics Values
    Surface Material Surface Material top-solid1
    top-solid2 [Interface 3]
    Physics Values
    Surface Material Surface Material top-solid2
The conditions for the wall boundary side-solid2 are the same as for side-solid1 and can be copied and pasted from the side-solid1 boundary.
  1. Copy the side-solid1 node and paste it onto the side-solid2 node.
  2. Save the simulation.