Finite differences on EnergyPlus and HoneyBee

grasshopper honeybee
1

Hello everyone !

I just read in the EnergyPlus documentation that heat transfert through walls is done by finite differences method. Then I have several questions :
1- Did you know if this method is one, two or three dimension set ?
2- If this is 2D or 3D, is it possible on HoneyBee to see a temperature surface mapping ?
3- If this is 1D, is it possible to create this map by cutting surface ? Then, is conduction between adjacent surface-parts is taken under account ?

Thank you in advance, for your answer and to Mostapha and Chris for everything :slight_smile:
Numa L.

2

Hi @Numa.Latourte ,

You can assume that all of EnergyPlus conduction calculations are 1D. There are a few modules in E+ that try to do a 2D conduction calculation just for the ground (eg. The KIVA model) but they are not exposed on any Honeybee components. So each Surface in EnergyPlus has only one indoor and outdoor temperature.

While essentially all conduction is 1D, all E+ Radiant heat transfer calculations are 3D and all convection calculations are semi-3D (the convective heat transfer calculations are sensitive to the orientation of each Surface at least).

Does that answer your question?

2 Likes
3

Sorry for not seeing this before my last answer. No it does not include and transfer between adjacent surfaces. Conduction is all 1D as I said.

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4

Hi @chris

Thank you very much for your answers ! It helps me a lot.

Respectfully,
Numa L.

5

Hi @chris

Another question is the default type of energy calculation in LBT is Conduction Transfer Function (CTF) or Finite Difference (FD)?

If it supports both, how can we choose?

Best,
Nariman

6

The only option in Honeybee right now is CTF and this is the default in EnergyPlus.

You can change it by writing a measure or editing the IDF in the IDFEditor.