Cooling Tower gpm/HP to EIR

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My mind is dead this morning. I can?t recall how to convert the 90.1 cooling tower fan power requirement to TWR-EIR for DOE2.2. For example, given 40.2 gpm/HP and convert Btu/Btu. Seems like you have to assume a delta-T for the condenser water flow in order to convert the gpm flow to Btu?

Christopher R. Jones, P.Eng.
Technical Specialist
Sustainability & Energy

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Jones, Christopher2's picture
Joined: 2017-10-12
Reputation: 0

Hi,

There was an old post back in 2012 on this topic. Here i am pasting the
excerpt from the post:

'*An axial fan cooling tower is required per G3.1.3.11. Required cooling
tower efficiency is 38.2 gpm/hp per ASHRAE 90.1, Table 6.8.1G. Let eQUEST
autosize the cooling tower, and use the design flowrate shown on the PV-A
report to determine the fan HP. Then convert to kW and enter the value in
FAN-KW/CELL. The cell is normally grayed out, so right-click the cell and
enter the kW value by changing the user default*.'

Moreover, I do follow the same in E+ too.

Hope this helps!

javed iqbal's picture
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Joined: 2012-05-18
Reputation: 0

Here?s an eQUEST expression from my toolbox that doesn?t see so much use in my current line of work. This saves you the implicit step of looking up the motor HP table (10.8) for efficiencies to determine the motor kW draw. It?s an example I commonly point to when teaching expressions to point out you can go pretty far with nested if/then statements if that?s how your mind is operating in the moment, but the results aren?t always so pretty to look at. It?s a good segue into introducing the wonderful world of switch statements. Regardless, this is functional enough:

TOWERS - kW per cell

This will determine a tower's fan power input in accordance with ASHRAE 90.1 Appendix G. Requires a #PA "Baseline CW Design GPM" which should be populated with the CW loop's GPM, following an auto-sizing run (re: PV-A or PS-D).

$Autosize your baseline tower's FAN-KW/CELL!

#PA("Baseline CW Design GPM")/38.2 $Actual HP requirement

*0.745699872 $HP to kW

/if(#PA("Baseline CW Design GPM")/38.2 < 1)

then .825

else if(#PA("Baseline CW Design GPM")/38.2 < 3)

then .840

else if(#PA("Baseline CW Design GPM")/38.2 < 7.5)

then .875

else if(#PA("Baseline CW Design GPM")/38.2 < 15)

then .895

else if(#PA("Baseline CW Design GPM")/38.2 < 25)

then .910

else if(#PA("Baseline CW Design GPM")/38.2 < 40)

then .924

else if(#PA("Baseline CW Design GPM")/38.2 < 60)

then .930

else if(#PA("Baseline CW Design GPM")/38.2 < 100)

then .936

else if(#PA("Baseline CW Design GPM")/38.2 < 150)

then .941

else .950

endif endif endif endif endif endif endif endif

endif $Incremental HP efficiency lookup, per T10.8

Hope this helps!

~Nick

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Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

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Nicholas.Caton at schneider-electric.com's picture
Joined: 2016-02-26
Reputation: 0

Thanks Nick,
Silly me, looking for TWR-EIR ? still back in DOE2.1e.

Christopher R. Jones, P.Eng.
Technical Specialist
Sustainability & Energy

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T +1 416-644-0252

2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4 Canada

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Jones, Christopher2's picture
Joined: 2017-10-12
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