[BLDG-SIM] Static Pressure Reset modeling in DOE 2

[Mark A. Webb]

Has anyone ever told you guys that you were nuts!  By the time you get
done with all of your guessing, manipulation, trickery, and manual curve
creation - you could have just made an intelligent guess and been
closer.  With the added bonus of saving a bunch of time.  Unless it is
some kind of PhD kind of thing.
 
Mark

	-----Original Message-----
	From: Steve Gates [mailto:stvgates at pacbell.net] 
	Sent: Wednesday, October 09, 2002 7:44 PM
	To: BLDG-SIM at GARD.COM
	Subject: [BLDG-SIM] Static Pressure Reset modeling in DOE 2
	
	
	Currently there is no "optimized static pressure control" for
fans/ducts in DOE-2.  However, J. Hirsch & Associates has funding to
implement such a mechanism in DOE-2.2 within the next few months.  The
funding is provided by Southern California Edison as part of their
"Energy Design Resources" program
(http://www.energydesignresources.com/).  These enhancement will be
incorporated into both DOE-2.2 and eQUEST (not PowerDOE), and will be
made available to the user community at no charge.
	 
	This control mechanism will be similar to the head reset
controls already implemented for variable-flow pumping systems in
DOE-2.2, where the pump head setpoint can be reset based on the hourly
head demand of the worst-case valve. The actual pump head is then a
function of the worst-case valve head, plus the additional variable-flow
head losses of the loop piping and the central plant equipment.  This
control sequence maximizes the potential savings of variable-speed
pumps, as the required speed of a pump is dependent on both the flow as
well as the head requirement; with the head requirement usually being
the dominant factor. (The maximum head of a pump varies roughly as the
square of the impeller speed; if the head requirement does not decrease
as the flow drops off, then the speed cannot decrease significantly).
	 
	For fans/ducts, the simple curve-fit that varies fan power as a
function of flow will become obsolete. Instead, DOE-2.2 will keep track
of the static requirement of the worst-case VAV box, as well as ducting,
coils, filters, etc.  Each component must be accounted for separately,
as the head of all of these devices varies differently for a given flow.
(Some components, such as ducts and sound traps, experience turbulent
flow, and their head varies as the 1.85 power of flow.  Other
components, such as coils and filters, are more laminar, and their head
typically varies in the range of the 1.1-1.6 power of flow.  Still
others, such as a VAV box without an intelligent DDC system to monitor
damper position, will have a constant head requirement; i.e. a constant
head setpoint out toward the end of the ducting.)  These changes will
require DOE-2.2 to know about the flow through each component in the
system, the component's head characteristic, as well as the fan map for
a given type of fan (forward-curved, airfoil, etc.)  Based on flow and
static requirement, DOE-2.2 will then be able to determine the fan speed
and power consumption.  
	 
	In the meantime, you can approximate "optimized static pressure
control" by generating a new curve that causes power to fall off more
rapidly with flow than the default curves.  However, this is not a
straightforward task, as you would have to calculate by hand all of the
algorithms we have designed for DOE-2, and repeat the calculations for a
series of flows.  Perhaps someone has already done this exercise, and
can share their curves with you.
	 
	Steve Gates

		----- Original Message ----- 
		From: babetsk at jbb.com 
		To: BLDG-SIM at GARD.COM 
		Sent: Wednesday, October 09, 2002 2:41 PM
		Subject: [BLDG-SIM] Static Pressure Reset modeling in
DOE 2

		
		To Doe 2 Users:
		 
		Hello,
		 
		Does anybody know if there is a way to model (in DOE-2)
an "optimized static pressure control", that is a control method where
the controller dynamically adjusts the static pressure set point based
on the position of the modulating devices in the VAV terminal units? 
		 
		Thank you
		 
		 
		Konstantin E. Babets, Ph.D.
		CFD/Energy Modeling Engineer
		Jaros Baum and Bolles
		Consulting Engineers
		80 Pine Street
		New York NY 1005
		Tel:   212.530.9455
		Fax: 212.269.5894
		
		 
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