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<DIV><FONT face=Arial size=2>Mark, </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>In many cases I fully agree with you about the
value of keeping the problem simple. Indeed, we have been criticized
numerous times in the past for DOE-2's 'overly simplistic' equipment
algorithms. Interestingly, when a couple of recent independent
studies compared DOE-2's chiller and cooling tower algorithms to more
sophisticated algorithms published in the literature, they found that
DOE-2's 'simple' algorithms gave the most accurate results. (One of these
studies found that the ASHRAE Toolkit chiller algorithm is so complex
that it is next to impossible to calibrate to manufacturer's data, and generates
errors on the order of +/- 10%; while DOE-2's accuracy was on the order of +/-
2%).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>But I have to disagree with you in the case of
variable-speed fans and pumps. How many of you have heard the claim of VSD
salemen that "power goes as the cube of the flow"? That claim is patently
false when applied to airhandlers and pumps. It is only true in the case
where the pressure falls off as approximately the square of the flow, such
as in a cooling tower, or a piping system with no valves. In the case of
systems where a significant portion of the pressure loss is associated with
non-turbulent components, pressure losses do not follow the flow-squared
law. And a fixed pressure setpoint further reduces the potential
savings. In fact, if the pressure setpoint is set high enough,
the VSD will run at full speed regardless of flow (I have observed this
situation).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>So it can make sense for DDC control systems
to reset the setpoint as a function of the pressure requirement of the
worst case component (but watch out for the rogue VAV box or coil!) And,
since one of our goals is to allow engineers to utilize DOE-2 to study the
cost-effectiveness of more sophisticated control sequences, the
program needs to do a better job of simulating this situation.
Granted, we will keep the algorithms as simple as is consistent with this
goal! And the default control sequence will utilize a fixed setpoint so
everyone can keep asking "how come the power consumption doesn't drop off as the
cube of the flow, like the salesman told me?"</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=MAW@abacus-engr.com href="mailto:MAW@abacus-engr.com">Mark A.
Webb</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=steve.gates@doe2.com
href="mailto:steve.gates@doe2.com">Steve Gates</A> ; <A
title=BLDG-SIM@GARD.COM href="mailto:BLDG-SIM@GARD.COM">BLDG-SIM@GARD.COM</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, October 10, 2002 4:11
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: [BLDG-SIM] Static Pressure
Reset modeling in DOE 2</DIV>
<DIV><FONT face=Arial size=2></FONT><FONT face=Arial size=2></FONT><BR></DIV>
<DIV><SPAN class=474480811-10102002><FONT face=Arial color=#0000ff size=2>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.</FONT></SPAN></DIV>
<DIV><SPAN class=474480811-10102002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=474480811-10102002><FONT face=Arial color=#0000ff
size=2>Mark</FONT></SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B> Steve Gates
[mailto:stvgates@pacbell.net] <BR><B>Sent:</B> Wednesday, October 09, 2002
7:44 PM<BR><B>To:</B> BLDG-SIM@GARD.COM<BR><B>Subject:</B> [BLDG-SIM] Static
Pressure Reset modeling in DOE 2<BR><BR></FONT></DIV>
<DIV><FONT face=Arial size=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 (<A
href="http://www.energydesignresources.com/">http://www.energydesignresources.com/</A>).
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.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Steve Gates</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=babetsk@jbb.com href="mailto:babetsk@jbb.com">babetsk@jbb.com</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=BLDG-SIM@GARD.COM
href="mailto:BLDG-SIM@GARD.COM">BLDG-SIM@GARD.COM</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, October 09, 2002
2:41 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [BLDG-SIM] Static Pressure
Reset modeling in DOE 2</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>
<DIV>To Doe 2 Users:</DIV>
<DIV> </DIV>
<DIV>Hello,</DIV>
<DIV> </DIV>
<DIV>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? </DIV>
<DIV> </DIV>
<DIV>Thank you</DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>Konstantin E. Babets, Ph.D.</FONT></DIV>
<DIV><FONT face=Arial size=2>CFD/Energy Modeling Engineer</FONT></DIV>
<DIV><FONT face=Arial size=2>Jaros Baum and Bolles<BR>Consulting
Engineers<BR>80 Pine Street<BR>New York NY 1005<BR>Tel:
212.530.9455<BR>Fax: 212.269.5894<BR></FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV></FONT></DIV><PRE>==================
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