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# what relationship among the Surface Outside Face,Surface Inside Face and Surface Average Face ?

In the e+ help document ,I think that Surface Inside Face Conduction Heat Transfer Rate + Surface Outside Face Conduction Heat Transfer Rate = Surface Average Face Conduction Heat Transfer Rate,but it was not rihgt, so I want to konw their relationship.

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The info that you're looking for is in the Opaque Surface Output Variables section of the EnergyPlus Input/Output Reference. Essentially, each variable corresponds to:

• Surface Inside Face Conduction Heat Transfer Rate: Conduction right at inside face of a surface. Positive values are for conduction towards the inside face.
• Surface Outside Face Conduction Heat Transfer Rate: Conduction right at outside face of a surface. Positive values are for conduction towards the outside face.
• Surface Average Face Conduction Heat Transfer Rate: Average conduction flowing through surface. Positive values are for conduction towards the inside face and zone (same sign convention as the inside face conduction variable).

I did a test of generating these three output variables for one surface, here are my results.

From this, it looks like the basic equation is $$Average Conduction = \frac{Inside Conduction - Outside Conduction}{2}$$

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Do you have tried to export the report from the Design Builder,？I did a test and found that “Walls+Ground Floors+Roofs” value in the DB report is equal to“:Zone Opaque Surface Inside Faces Total Conduction Heat Gain Rate—Zone Opaque Surface Inside Faces Total Conduction Heat Loss Rate "，as also as“Surface Inside Face Conduction Heat Transfer Rate ” . But I wonder that why it is nothing to do with “ Outside Face Conduction ”，I think it should be equal to Surface Average Face Conduction Heat Transfer Rate .

these three output variables for one surface, here are my results.

( 2018-08-30 21:50:12 -0500 )edit

The Output Options documentation for DesignBuilder say that "Surface heat transfer" graphable outputs generates inside face conduction, but not the others. You may be able to include the others if you use the "Store surface output" option and select "Surface Heat Gain" for the surfaces in the model you are interested in analyzing.

( 2018-09-03 15:30:37 -0500 )edit

if you are losing heat from the inside by conduction (inside face conduction heat tranfer). That loss should be greater than the flow of heat that reaches the outside by conduction (outside face conduction heat tranfer), since a part is stored. However, I do not see that in your the results

( 2018-09-27 09:57:30 -0500 )edit