[BLDG-SIM] Boiler Performance Curves

[Mike Tillou]

Wade,
 
You can make your own HW-Blr-HIR-fPLR cubic curve for PowerDoe using Excel.
You can plot boiler efficiency and the boiler input ratio (as defined by
powerdoe) and create a third order polynomial trend line of the resulting
graph.  Have Excel display the trendline equation and then input the
coefficients into a new curve fit in Powerdoe.  The Powerdoe Help files and
documentation do a good job of discussing how curve fits work and how to
create your own.  There is also a detailed help screen that discusses the
Boiler Heat Input Ratio.
 
If you add your curve fits to a custom library they will always be there for
you to use.
 
Good luck,
 
 
Mike Tillou, PE
etc Group, Inc.
SLC, Utah
 
 
-----Origi  nal Message-----
From: postman at gard.com [mailto:postman at gard.com] On Behalf Of Wade
McLaughlin
Sent: Wednesday, February 12, 2003 12:05 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Boiler Performance Curves



Hello All,
 
As part of a comprehensive energy study for a new elementary school, we are
analyzing fuel savings opportunities for a proposed boiler with fully
modulating burners as compared to a base-case sectional lo-hi-lo boiler.  So
far, we have found that, all things being equal, there are no significant
savings associated with such a measure (at least not for the boiler size and
models we've been considering).
 
We use PowerDOE for most of our energy simulations.  In the course of this
study, we have come to question the default boiler part-load
heat-input-ratio curve (HW-Blr-HIR-fPLR) found in Bdllib.dat.  Until now, we
have applied this curve to most base-case boiler calculations (perhaps
mistakenly?).  Does anyone know of the origins of this curve or what it
would have been based upon?  Most manufacturers we have spoken with state
that peak boiler efficiency occurs between 25% and 50% load.  Using the
default curve, peak performance occurs at full load and efficiency decreases
by nearly 10% at half load.
 
Also, if this curve is in error, can anyone suggest a method for developing
a more reasonable curve estimate?
 
Thanks,
Wade
 
Wade McLaughlin
DMI
450 Lexington St.
Newton, MA  02466
p 617-527-1525 x103
f  617-527-6606


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