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[EnergyPlus_Support] I wonder a part of AFN algorithm

Hello fellows 
I wonder a part of AFN algorithm, especially the consideration of stack effect. I have read many text and E+ engineering references, but can't find the answer of my question. 

As you know, bascially the air mass flow is based on the power law equation like below 
air mass flow(M)=C*(dP)^n

the pressure difference of two consecutive nodes (dP) in AFN is (Static P1 + Dynamic P1 + Stack P1) - (Static P2 + Dynamic P2 + Stack P2).
But generally this kind of Bernoulli's Equation assumes density as the constant. 
If so, Stack P (=rho*g*h) is just the function of height. 
Because the density and gravity acceleration are constant.

If so, how that equation considers pressure difference from temperature difference? 

I think AFN consider stack effect in this way but can't sure right or not(I can't find the detailed assumption from Engineering reference). 
If I apply treat the air as an Ideal Gas 
Density(rho)=P/RT
Then the density is function of Temperature like this (Because R is constant and P would be 101.325kPa)
or from the linear assumption
rho=2.7567-0.0053T
then the Stack pressure rho*g*h can consider the pressure difference from temperature diffrerence also.

I look foward to get an answer of my question.  
Thanks in advance. 

Best regards. 




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