Internal Source

Internal Source tab on Constructions Dialog.

The internal source tab is visible only when the model is set to use Detailed HVAC. It allows data on the position and nature of any heating or cooling pipes included within the construction. Internal sources are associated with one of these components:

• Heated floors or Chilled ceiling components by virtue of the construction being selected as the floor/ceiling in a zone with heated floor or chilled ceiling defined. For example in the case of a heated floor the heated floor component must be added to the appropriate HVAC zones, but also a floor construction with an internal source must be associated with at least one floor surface in that building zone. If you set up a model with a heated floor added to an HVAC zone whose equivalent building zone has any floor surfaces with a floor construction selected not having an internal source then an error will be generated.
• Ground loop heat exchangers of the type 3-Surface to define the location of the heat exchanger pipes.

Internal source

Check this option if the construction includes a heating or cooling source.

Layer after which the internal source is positioned

Enter a number between 1 and 1-the number of layers. Entering 1 means that the source is positioned between the outermost layer and the next layer. If you are defining a heated floor construction then you will normally enter 1-the number of layers. The easiest way to do this is to use the Set source position below innermost layer tool described below. When defining a chilled ceiling as a floor construction you should enter a value of 1 here.

Important Note: The internal source must be placed thermally closer to the inside surface than to the outside surface of the construction to allow it to be considered for inclusion in a zone's radiant surface, heated floor or chilled ceiling system. In other words, if the thermal resistance between the inside surface and the internal source is less than the resistance to the outside surface then the surface is considered to be a valid radiant surface to be included with the zone next to the inside surface and will be simulated as such. This rule applies to surfaces adjacent to outside as well as internal surfaces.

Dimensions

This field refers to the detail level of the calculation. Select from the 2 options below for a 1-D or 2-D solution:

• 1-D is the default choice for a one-dimensional calculation. This is appropriate for hydronic heating/cooling when water heater/cooler performance is relatively unaffected by return and supply water temperatures.
• 2-D triggers a two-dimensional solution. With 2-D solutions, the calculation of the conduction transfer functions (CTF) is fairly intensive and requires extra simulation time. Note that with the 2-D option the solution regime is two-dimensional internally but it has a one-dimensional boundary condition imposed at the inside and outside surface (i.e., surface temperatures are isothermal).

Note: Because the 1-D solution method does not allow the return water temperature to be accurately calculated it is not recommended for when accurate plant energy consumption outputs are required. In this case choose the 2-D option.

The 2-D solution method generally takes about 20% longer to run a simulation relative to the 1-D option.

Tube spacing

This field defines how far apart (in m or in) the hydronic tubing are spaced in the direction perpendicular to the main direction of heat transfer. This parameter is used when either the 1-D or 2-D Dimension setting is selected (above).

Set source position below innermost layer

A tool is provided in the info panel when using learning mode which calculates which is the innermost layer and adds the source between this and the next layer. For example in a chilled ceiling construction you might have 0.5 mm steel ceiling panel as the innermost layer with 3 other layers. In this case when clicking on the Set source position below innermost layer link, the innermost layer value would be set to 3.

Note: Constructions with an internal source cannot be used in ground surfaces which are adjacent to a Kiva Foundation. You can use surfaces with an internal source in any other surface in Kiva simulations though.