[Bldg-sim] PowerDOE Steam Loops

Steve Gates stvgates at pacbell.net
Wed Jul 31 09:50:19 PDT 2002


As you are aware, the program does not fully address steam loops. Steam loops consist of a myriad of components, many of which experience large thermal losses, and are prone to failure (such as steam traps)

One way to approximate a steam loop is to model it as a single hot-water loop, but specifying a steam boiler.  The steam boiler default efficiency is reduced to take into account some of the losses associated with the de-aerator and other parasitic devices; however the parasitic losses were not well-researched, and the default efficiency is simply an semi-educated guess. (I came up with the value after thinking about it for a total of 5 minutes).

Steam loops tend to have HUGE annual losses; I believe that in most cases they exceed the actual annual end-use load. Throw in a couple of malfunctioning steam traps and they can be ridiculous. In spite of the fact that DOE-2.2/PowerDOE/eQUEST can model piping losses, most people neglect them, thinking they are small.  They are NOT small in most cases.

You should definitely specify the piping UA so the program can calculate losses. To better account for the UA split between the hot-water and steam loops, you could model a primary/secondary loop arrangement, where the primary loop is the "steam" loop, and the secondary loop is the hot-water loop.  To make the pumping energy of the "steam" loop match the actual pumping energy (condensate, de-aeration, and pressurization), you can adjust the head loss of the piping, boiler, and valve modulating flow into the secondary loop.

Hot-water loops can also have very large losses; I have found that the losses in VAV/hot-water reheat systems typically exceed the annual reheat load.
  ----- Original Message ----- 
  From: Wade McLaughlin 
  To: Bldg-sim at gard.com 
  Sent: Wednesday, July 31, 2002 10:42 AM
  Subject: [Bldg-sim] PowerDOE Steam Loops


  In PowerDOE:  I have a number of VAV Roof Top Units with steam heating coils.  Zone reheat is handled using hot water, and the hot water loop is heated with steam from the steam loop.  Does anyone have a good suggestion as to how to model heat exchange between the steam and hot water loops?

  Thanks,

  Wade McLaughlin
  DMI
  450 Lexington St.
  Newton, MA  02466
  p 617-527-1525 x103
  f  617-527-6606

==================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM




===========================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20020731/a9ea41ac/attachment.htm>


More information about the Bldg-sim mailing list