Question about Hb_Therm Boundary Condition

[Sadmummy]

Hello,

I want to use BC radiation model to simplified

Someone asked the same topic in the old forum but I cannot find how to apply in Honeybee

Is there a way to apply simplified in Honeybee? or I have to run the Therm separately and Import the result.

http://www.grasshopper3d.com/profiles/comment/list?attachedToType=User&attachedTo=30sklngzvpedl
this link is the same topic in old forum

[chris]

@Sadmummy ,

This discussion has some information about how to customize the boundary conditions:

THERM - Control over BC Radiation Model

Grace and Jonathan, Thank you so much for all of the information. I also did some research over the last few hours and I can confirm that you are correct. NFRC states that we’re supposed to use a black body with view factor 1 for the exterior. Accordingly, I have set this as the default whenever anyone plugs in the words ‘outdoor’ for the film coefficient or plugs in a convective film coefficient greater than 10 W/m2K (which is pretty certainly an outdoor condition). You can see the changes …

The “Custom Rad Environment” component allows you to change pretty much all of the parameters of the boundary conditions you might need to change.

This said, I didn’t expose the use of the simplified BC model in Honeybee and all of the Honeybee THERM exports use the comprehensive model. I did this because you should be able to get matching results with the simplified model by customizing the comprehensive model with the right inputs. Is there a particular reason why you need the simplified model? I know NFRC does not use it and I’m curios to know if there’s some standard that requires it.

[Sadmummy]

Thank you for your reply.
Actually, I’m not familiar with Therm because my company uses thermal bridge calculator named Heat2.
Heat2 is validated against the standard EN ISO 10211 and EN ISO 10077-2.
I want to use HB therm in my work, so I crosschecked simulation values Therm and Heat2.
HB Therm(no input in customRadenv_createThermBoundaries) and heat2 simulation result show pretty different values. But run the therm by itself using simplified radiation shows similar values.
Maybe It is obvious that the BC condition is different. So I asked how to apply the simplified model.
Recently, I found “blackbody with view factor 0” shows similar to the heat2 and simplified model.
But there is no the theoretical backup. )

[chris]

@Sadmummy ,
Thanks for the explanation and your workflow for matching results with the simplified method makes sense. When you see the viewFactor to 0, you cut off all of the radiant transfer calculation, so I’m assume that you’d account for this by incorporating radiant heat transfer in the film coefficient (which is normally only for convective heat transfer in the comprehensive model). What film coefficient are you typically using? If it’s more than 4 W/m2-K, it is probably intended to include the radiant heat transfer.