[Bldg-sim] EE4 (DOE-2.1E) Water-Side Economizer Issue

Chris Jones cj at enersave.ca
Wed Jul 25 05:23:00 PDT 2012


 From the DOE2.1E Supplement:
DIRECT-COOL-KW
specifies the electrical input to direct cooling auxiliary equipment.
The default varies according to the direct cooling mode.
IT DIRECT-COOL-MODE = THERMO-CYCLE, you should
specify DIRECT-COOL-KW as kW /ton of operating capacity
for the period during which the compression chillers are operating
in this mode. The chiller electrical input is assumed to be
DIRECT-COOL-KW multiplied by the operating capacity
and the fraction of the hour the chiller ran. If
DIRECT-COOL-MODE = STRAINER-CYCLE, you should
specify DIRECT-COOL-KW as the electrical input to the
condenser water pumps (and other added equipment), calculated
as kW /ton of SYSTEMS peak cooling load. Usually, this
value is zero as the chilled water pumps are assumed to provide
all motive energy. If a heat exchanger is used to isolate the
tower from the chilled water loop, then this value should be
non-~ero to model the condenser pumping energy. In this case,
the condenser water pumping energy is calculated using the
value of DIRECT-COOL-KW as the kW per ton of the design
SYSTEMS load. (Fluid flow to the tower is assumed to be the
design chilled water flowrate). For both modes of direct cooling,
THERMO-CYCLE and STRAINER-CYCLE, the chilled
water pumps are assumed to run as usual.

At 01:35 PM 24/07/2012, Jake Martell wrote:
>Hello,
>
>-I am looking to simulate a water-side economizer in EE4 (DOE-2.1E) 
>by altering the .doe file.
>-I have added the highlighted text below into the "Plant-Parameters" 
>section of the .doe file.
>
>
>PLANT-PARAMETERS
>       BOILER-CONTROL     = STANDBY
>       HW-BOILER-HIR     = 1.0870
>       CHILLER-CONTROL    = STANDBY
>$ Cooling Tower $
>       TWR-SETPT-CTRL     = FIXED
>       TWR-SETPT-T        = 85.0
>       TWR-DESIGN-WETBULB = 73.0
>       TWR-DESIGN-APPROACH= 12.0
>       TWR-DESIGN-RANGE   = 10.0
>       TWR-THROTTLE       = 5
>       TWR-CAP-CTRL    = ONE-SPEED-FAN
>       TWR-CELL-CTRL      = MIN-CELLS
>       DIRECT-COOL-MODE = STRAINER-CYCLE
>       DC-MAX-OAT = 39.0
>       DC-MAX-CHILL-WTR-T = 44.0
>       DC-TWR-WTR-SETPT = 44.0
>       DIRECT-COOL-KW = 0.055
>$ Condenser Water Pumps $
>       TWR-MOTOR-EFF      = 0.917
>       TWR-IMPELLER-EFF   = 0.790
>       TWR-PUMP-HEAD      = 60.00
>  ..
>
>
>
>-After running the simulation and comparing it to previous results, 
>there are savings on "Space Cooling" but there is also a greater 
>energy usage in "Heat Reject" as show in the table below.  The DOE-2 
>guide suggests entering the condenser water pumping power as kW/ton 
>but maybe I should be entering 0 for DIRECT-COOL-KW if I'm 
>accounting for the condenser water pumps twice?  This is for a 
>project in Nova Scotia so I think there should be savings from 
>turning off the chillers throughout the winter but it doesn't make 
>sense based on these results.
>
>Energy Use Category
>Before Change
>After Change
>Savings
>
>
>
>(MBtu)
>(MBtu)
>(MBtu)
>% Sav
>
>Area Lights
>2,252.2
>2,252.2
>0
>0.0%
>
>Misc. Equipment
>1,629.1
>1,629.1
>0
>0.0%
>
>Space Heat
>2,062.0
>2,062.0
>0
>0.0%
>
>Space Cool
>615.6
>475.7
>140
>22.7%
>
>Heat Reject
>121.5
>295.6
>-174
>-143.3%
>
>Pumps & Misc.
>1,136.2
>1,136.2
>0
>0.0%
>
>Vent Fans
>2,168.4
>2,168.4
>0
>0.0%
>
>DomHot Water
>587.6
>587.6
>0
>0.0%
>
>TOTAL
>10,572.6
>10,606.8
>-34
>-0.3%
>
>
>
>Best regards,
>
>Jake R. Martell, EIT
>Mechanical Engineer-in-Training
>[]
>
>t: (902) 422-7393
>f: (902) 423-4945
>e: <mailto:jmartell at mreng.ca>jmartell at mreng.ca
>
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 >>
Christopher Jones, P.Eng.
Suite 1801, 1 Yonge Street
Toronto, ON M5E1W7
Tel. 416-203-7465
Fax. 416-946-1005
email cj at enersave.ca
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