[Equest-users] Multiple DOAS in Series

[Kathryn Kerns]

Carol, I am not sure I understand what you mean. Can you draw a picture or explain further? If I have one DOAS, how do I go about specifying entering conditions for its ERV other than outside air and exhaust?
 
I am also wondering just exactly what happens to DOAS supply air. According to the literature it appears that the outside air is fed through the DOAS, which then heats it and cools it via the DOAS entered heating and cooling supply temperatures, and then the supply air is passed to the associated space air (which I assume has the normal space temperature range of 70 to 78) which it then transmitted to the downstream terminal units as their primary air. At least I think this is what I think I read.
 
Does anyone else have a different interpretation? Maybe we are passing the DOAS supply air to the terminal units at the supply heating and cooling temperatures the same way the DOAS supply air gets passed to its associated space?
 
If I figure this out, I will share the results. Desiccant systems like the one I am modeling are being used more and more often as energy savers in humid climates. Somehow we need to figure this out or come up with an equivalent.

________________________________

From: Carol Gardner [mailto:cmg750 at gmail.com]
Sent: Mon 10/18/2010 7:45 PM
To: Kathryn Kerns
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Multiple DOAS in Series


Hi Kathryn,

Just a couple of quick thoughts. Do you need to physically specify 2 DOAS units? Could you just specify one with an ERV and with the entering conditions of the first unit and the leaving conditions of the second unit? I'm not thinking of any downside to doing it that way but I'm not deep in it like you are. Let me know what you think.

Cheers,

Carol


On Mon, Oct 18, 2010 at 2:06 PM, Kathryn Kerns <kathryn.kerns at bceengineers.com> wrote:


	Has anyone ever tried to model 2 DOAS units in series? I have successfully modeled a single DOAS/multiple fan coil system, but I have never tried to string two DOAS units together by feeding the supply air output of the first DOAS into the outside air input of the second DOAS. The reason I ask is that I am looking for a way to model a DOAS that has an ERV device located downstream after a heating and a cooling coil.  Does anyone know whether DOE-2 would treat the system exhaust air coming back through the second DOAS ERV any differently than the exhaust air going back through a single DOAS with an ERV unit? 

	 

	Assuming that this works, does anybody know how to add heat to, or manually raise the temperature of, the ERV exhaust air? 

	 

	I am thinking if I can model a multiple DOAS with an elevated exhaust temperature, I might be able to mimic a desiccant system. According to James Hirsch in California, the energy balance used in the desiccant tabs is not correct and should not be used, so I am out of luck there.

	 

	If anyone has another method for modeling a desiccant system, I would love to hear from you.

	 

	Kathryn Kerns

	Systems Specialist

	BCE Engineers, Inc.

	| Ph: 253.922.0446 | Fx: 253.922.0896 | 

	 

	 


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-- 
Carol Gardner PE

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