How to set sources

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Content

Introduction

What are direct sources?

How to use direct sources?

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A source is where heat enters your case. On ColdStream there are two types of sources: indirect sources and direct sources. Direct sources are controlled by the user during the case setup. A user has the ability to specify this heat input during the case setup. On the other hand, indirect sources are unaffected by the user during the case setup. For example, viscous dissipation in the fluid region(s) will always be activate when a case is running.

This article focuses solely on how you can correctly use direct sources on ColdStream.

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Direct sources are heat inputs specified directly by the user during the case setup. These sources are due to Joule heating, chemical reactions or some other phenomenon.
This quantity of heat (\(\dot{Q}\)) is spread out evenly over the entity on which it is defined, meaning that:

• if the heat input (\(\dot{Q}\)) is specified on a surface patch: the local heat map (\(q \space\space in \space\space [\frac{W}{m^2}]\)) is uniform:
  \(q = \frac{\dot{Q}}{A}\)
  Where A is the area of the surface patch.
• if the heat input (\(\dot{Q}\)) is specified on a (sub)region: the volumetric heat map (\(q \space\space in \space\space [\frac{W}{m^3}]\)) is uniform:
  \(q = \frac{\dot{Q}}{V}\)
  Where V is the volume of the (sub)region.

If the input value is negative, the heat source becomes a heat sink. This means that instead of heat entering through that entity, it leaves through that entity.

As stated earlier, direct sources are specified by the user during the case setup. A user has the choice to include a heat source for all entities (regions, subregions and surface patches) available in the geometry. The following subsections go into more depth on how to assign these heat sources for each of the entities individually.

Direct sources on regions and subregions

During the case setup, all regions (not including the subregions) have an input field for a heat source (Q). By default it is set to 0, meaning no heat is entering or leaving through it. Fill in the required value if you want to overwrite that default value.

As stated in the previous section, the inputted value is distributed uniformly over the entire volume. In case you want a more localised heat production, you can include a subregion. This subregion must be of type 'general', not of type 'design'.
The heat source input field is identical to the one of a parent region. However, the heat is now distributed uniformly in that subregion only, not in the entire parent region. You can include as many subregions as you like, as long as they don't overlap. Be warned though, the more regions you include, the longer it will take for the platform to complete your case.

Direct sources on surface patches

There are only two types of surface boundary conditions which allow you to specify a direct heat source. These are the heatedWall boundary condition and the insulatedWall boundary condition.

The heatedWall boundary has the same heat source input field as the regions and subregions have. The inputted value will be distributed uniformly over the entire area of this surface patch.
An insulatedWall does not allow any heat to be transferred through it. This means that you explicitly tell ColdStream that it is not possible for heat to enter or leave this surface patch. An insulatedWall is also assumed wherever a region does not have an interface with another region.