THCP thermal property and orientation settings

[Marco Aldegheri]

Hello everybody!

I tried searching to see if the topic had already been discussed, but I couldn't find any posts about it. I hope I'm not creating redundancies.

I have a question about an FDS model. My intent is to perform a structural analysis of a steel structure in SAFIR, and I'm using FDS to obtain temperature profiles near columns and beams. The temperatures obtained from the CFD model will be assigned to the steel sections of the thermostructural model.

I imagine that the surface steel profiles' temperatures should be obtained using thermocouples:

&DEVC ID='THCP-1-1', QUANTITY='THERMOCOUPLE', XYZ=4.0,4.0,1.0, ORIENTATION=0.0,1.0,0.0/

By default, FDS uses 1mm for bead diameter, 0.85 for emissivity, 8908 for bead density, and 0.44 for bead specific heat. These parameters describe the thermal properties of the thermocouple.

My question is this: I'm looking for the temperature for the steel beam profile... should I change the THCP properties and use the thermal properties for steel material? Is correct to se THCP?

I also have a doubt about the ORIENTATION settings. How should I set this parameter? I guess I should point it towards the fire to capture radiation, but changing this parameter doesn't seem to yield any variation in results.

(Used the following and give tha same results

&DEVC ID='THCP-1-1', QUANTITY='THERMOCOUPLE', XYZ=4.0,4.0,1.0, ORIENTATION=0.0,1.0,0.0/

&DEVC ID='THCP-1-01', QUANTITY='THERMOCOUPLE', XYZ=4.0,4.0,1.0, ORIENTATION=0.0,-1.0,0.0/

)

Thanks for your help!

[dr_jfloyd]

THERMOCOUPLE does not measure the solid temperature. See User's Guide 22.13 Solid Phase Output Quantities

[Marco Aldegheri]

Goodmorning,

thanks jfloyd  for the answer. I have delved into the aspects related to input for deducing thermostructural aspects and the temperature deduced by FDS. Indeed, for my case, and also considering some publications (https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=900083; https://www.researchgate.net/publication/319558322_FIRE_ANALYSIS_OF_A_NEW_STEEL_BRIDGE) , the input to be deduced from FDS to define the thermal action on structures should be obtained through the output ADIABATIC SURFACE TEMPERATURE. This value must then be imposed on the verification section in the thermostructural software.

Please correct me if I'm wrong. 

Thank you.

Marco

[dr_jfloyd]

The AST is an effective exposure temperature. It is a useful way to represent the thermal conditions in FDS inside of a more detailed thermal model; however, I am not a SAFIR user and do not know what specific inputs SAFIR allows or requires. You should compare the description of the AST in the FDS Guides with the description of inputs for SAFIR and satisfy for yourself that the AST is the correct quantity.