Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Unit inducing mistake when you set a Cooling Tower in OpenStudio / EnergyPlus

asked 2018-01-27 14:19:47 -0500

updated 2018-01-28 08:05:49 -0500

Only to inform other users, if you are setting Cooling Tower, if you use Evaporation Loss Mode: Loss Factor, you will need to set Evaporation Loss Factor.

The unit showed is percent/K. So, InputOuputReference indicates a typical value from 0,15 to 0,27 [percent/K].

But you need to set in program 0,0015 to 0,0027 to result in reasonable results. In other words, you need "to do the percent" before you set this parameter. If not, the results are unreals.

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2018-01-27 15:53:56 -0500

Your right. The documentation does show units of percent. Same for the next field of drift loss percent. A review of the code shows that the Evaporation Loss Factor field is currently a fraction, not percent, of water flow rate.

The IDD shows the same information described in the Input Output Reference document:

N19, \field Evaporation Loss Factor
   \type real
   \units percent/K
   \note Rate of water evaporation from the cooling tower and lost to the outdoor air [%/K]
   \note Evaporation loss is calculated as percentage of the circulating condenser water rate
   \note Value entered here is percent-per-degree K of temperature drop in the condenser water
   \note Typical values are from 0.15 to 0.27 [%/K].
   \default 0.2
N20, \field Drift Loss Percent
   \type real
   \default 0.008
   \units percent
   \note Rate of drift loss as a percentage of circulating condenser water flow rate
   \note Typical values are between 0.002 and 0.2% The default value is 0.008%

And the code where these data are read in shows:

SimpleTower( TowerNum ).UserEvapLossFactor = NumArray( 19 ); //  N11 , \field Evaporation Loss Factor
SimpleTower( TowerNum ).DriftLossFraction = NumArray( 20 ) / 100.0; //  N12, \field Drift Loss Percent
edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools


Asked: 2018-01-27 14:19:47 -0500

Seen: 192 times

Last updated: Jan 27 '18