[TRNSYS-users] trnflow16 - atrium

[jeannieboef]

1) Is it possible that the crack will only see a dP due to the air  
thermal stack effect, not due to any negative pressure created by the  
exhaust fan?

2) Are their other cracks on the bottom zone?

Usually the fan dP entry for simulations is static and the volume flow  
is static. This means the volume will flow into the bottom zone. In  
Trnsys the exiting mass flow is checked but usually not used in the  
calculations. This means modelling an exhaust fan in the top zone  
equates to only modelling a cross mixing in the top zone with the  
bottom zone air being referanced for the air properties.

In real life your exhaust fan will be a constant volume fan, meaning  
it will spin slower or faster to create the nessecary pressure dP to  
make sure the specified volume goes through it.

I would model the "exhaust fan" as a fan bringing air from the bottom  
zone into the top zone and equate it's mass flow to that of the supply  
fan. The exhaust fan dP should then be equated to the normal pressure  
losses of ducting minus the fortunate effect of the thermal stack  
effect.



Sent from my iPhone

On 14.05.2012, at 09:39, Mariëlle Nuchelmans <M.Nuchelmans at chri.nl>  
wrote:

> Hello,
>
>
>
> I have a problem regarding trnflow (version 16). I have got to model  
> the following:
>
>
>
> An atrium 2 zones heigh
>
> A mechanical ventilation systeem, supply in the bottom zone, exhaust  
> in the topzone (temperature 18 degree celsius)
>
>
>
> I made a simple model:  EN                        – AN               
>              –  FA                                        –  
> CR                               –    FA                             
>           -  EN
>
>                                                Outside – temperature 
>  18 degree – fan into bottom zone – cr between zones -  exhaust  
> fan to outside -  outside
>
>
>
> Problem is that when I plot the flow through the crack, the results  
> doesn’t made sense. For example: the fan delivers 120 kg/h, through  
> the crack goes 25000 kg/h??
>
>
>
> Crack has a Cs of 1 kg/s at 1 Pa.
>
>
>
> If anyone got any ideas where to look for the solution, please let  
> me know.
>
>
>
> With kind regards,
>
>
>
> Mariëlle
>
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at cae.wisc.edu
> https://mailman.cae.wisc.edu/listinfo/trnsys-users