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 iPhoneOn 14.05.2012, at 09:39, Mariëlle Nuchelmans <M.Nuchelmans@chri.nl> wrote:
Hello,I have a problem regarding trnflow (version 16). I have got to model the following:An atrium 2 zones heighA 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 - ENOutside – temperature 18 degree – fan into bottom zone – cr between zones - exhaust fan to outside - outsideProblem 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@cae.wisc.edu https://mailman.cae.wisc.edu/listinfo/trnsys-users