Horizontal heat transfer doesn't work

[rpeacoc]

Consider a case with a fire compartment with steel walls with an opening only to the outside. The compartment is adjacent to another compartment (with steel walls) and the two compartments are specified by the HHEAT command to be connected for horizontal heat transfer. The second room show both warm and rise in pressure due to the conduction of heat from the fire room. That doesn't seem to work in version 7.1. sample input file attached.

HHeat.txt

[rpeacoc]

This is an interesting question that's pointed out a significant limitation in the CFAST GUI for data input. Before I start, it's also important to note that the inter-compartment heat transfer is only potentially important with high-conductive surfaces, e.g. steel, connecting the two compartments

The compartment to compartment heat transfer does work, but the inputs generated by the GUI for the model are too limited. For example, consider two square rooms with one wall connected. If you tell the GUI that 25 % of room 1 is connected to room 2 you get a single input line that looks like

HHEAT 1,1,2,0.25

This says that 25 % of room 1 is connected to room 2, but doesn't say what to do with the other 75 %. The correct input line in the simplest case should be, for example

HHEAT 1,2,2,0.25,3,0.75

This one says that 25 % is connected to room 2 and the rest (75 %) is connected to the outside (room 3 in a two room case). We'll need to fix the GUI to do this correctly, but it's still not the most general case. Part of room 1, for example, could also be connected to another room. In addition, this input (from CFAST's point of view), doesn't actually say anything about how room 2 is connected to room 1 and the model then assumes that room 2 is actually just all connected to the outside. For the simulation to actually work, you need two inputs such as

HHEAT 1,2,2,0.25,3,0.75
HHEAT 2,2,1,0.25,3,0.75

This says that 25 % of room 1 is connected to 2 room AND 25 % of room 2 is connected to room 1 (the rest is connected to the outside like before) . If there's a fire in room 1 the model works as expected, heating room 2 just because its wall is connected to room 1.

We're working on fixing the GUI for the next release.

[rpeacoc]

Revision 0605fd5 adds checks to make sure heat transfer fractions add to 1. Still need to fix the output file for HHEAT

[rpeacoc]

This should be resolved in revision 59b51e0. CFAST and GUI support correct format for horizontal heat transfer.