I was wondering sometime why the head required is so low for the tube alone.
I think, the simple calculated low value assumes that there are no restrictions at both ends of the tube. The pressure required to force the air into the zone is not taken into account.
Calculated fan power can also be very low, probably because the blade size, surface friction, etc. were not taken into account. All these are hidden in the efficiency value of the fan.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: wasilqayyum@xxxxxxxxxxx
Date: Fri, 1 Jul 2011 19:48:50 +0000
Subject: [EnergyPlus_Support] Re: How to calculate Fan Pressure Rise
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Primary EnergyPlus support is found at:
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The primary EnergyPlus web site is found at:
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I think, the simple calculated low value assumes that there are no restrictions at both ends of the tube. The pressure required to force the air into the zone is not taken into account.
Calculated fan power can also be very low, probably because the blade size, surface friction, etc. were not taken into account. All these are hidden in the efficiency value of the fan.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: wasilqayyum@xxxxxxxxxxx
Date: Fri, 1 Jul 2011 19:48:50 +0000
Subject: [EnergyPlus_Support] Re: How to calculate Fan Pressure Rise
Thanks for the answer.
I do infact know how to calculate pressure drop etc. But I get very low results like 8 Pa (just the horizontal section of earth tube). Whereas, the values often used is around the 400 Pa range. So my really value has left me confused.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@...> wrote:
>
> I have never used this object. I assume that it is the same as the hvac fan objects, meaning that a direct relationship exists between air flow Q, total efficiency, nominal rated pressure rise dP and Nominal Rated Power E.
>
> To calculate dP you need
> Power (W)
> Flow (m3/s)
> Total Efficiency ()
>
> If you don't have Power and you really must calculate the pressure drop in your pipes at a specific mass flow, then you'll need to dust off the old fluid mechanics text books, find the section on Reynolds numbers and flow in rectangular or circular ducts and hand calculate it. Or find some other program to do it.
>
> I don't know if E+ has something on their site to do this? Basic slide rule stuff. I think one can simulate it as well, but I've never done it.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "wasilqayyum" <wasilqayyum@> wrote:
> >
> > Hello,
> >
> > There is a field in zone earth tubes called "Fan Pressure Rise". Can someone please tell me how to calculate this value?
> >
> > Thanks.
> >
>
I do infact know how to calculate pressure drop etc. But I get very low results like 8 Pa (just the horizontal section of earth tube). Whereas, the values often used is around the 400 Pa range. So my really value has left me confused.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@...> wrote:
>
> I have never used this object. I assume that it is the same as the hvac fan objects, meaning that a direct relationship exists between air flow Q, total efficiency, nominal rated pressure rise dP and Nominal Rated Power E.
>
> To calculate dP you need
> Power (W)
> Flow (m3/s)
> Total Efficiency ()
>
> If you don't have Power and you really must calculate the pressure drop in your pipes at a specific mass flow, then you'll need to dust off the old fluid mechanics text books, find the section on Reynolds numbers and flow in rectangular or circular ducts and hand calculate it. Or find some other program to do it.
>
> I don't know if E+ has something on their site to do this? Basic slide rule stuff. I think one can simulate it as well, but I've never done it.
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "wasilqayyum" <wasilqayyum@> wrote:
> >
> > Hello,
> >
> > There is a field in zone earth tubes called "Fan Pressure Rise". Can someone please tell me how to calculate this value?
> >
> > Thanks.
> >
>
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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