[Bldg-sim] Modeling a Cooling Tower

Timothy Moore timothy.moore at iesve.com
Thu Mar 26 12:34:19 PDT 2009


For those of you who missed the post the other day regarding modeling of
water-cooled chillers, chilled water loops, and HVAC systems more
generally in IES <Virtual Environment> (see "One Model" discussion
thread just a couple days ago), the following excerpt duplicates the
text from that post regarding water-cooled chillers, chilled water
loops. The discussion of currently offered capability along these lines
follows the description of the development that is soon to be released.

 

***

 

Regarding the modeling of water-cooled chillers, chilled water loops,
and HVAC systems in IES <Virtual Environment>:

 

While not yet publically released or announced, in-depth capability for
modeling water-cooled chillers and chilled water loops within the IES
<Virtual Environment> ApacheHVAC application has been developed and
implemented. This capability is presently undergoing testing and will be
available in the next release later this spring. 

 

The new water-cooled chiller model is described by three performance
curves: 

1)      varies cooling capacity with entering condenser water
temperature

2)      varies electric input ratio (EIR) with chilled water temperature

3)      varies electric input ratio (EIR) with part-load fraction. 

 

These scalable performance curves are pre-defined for common chiller
types: screw; centrifugal (hermetic, with or without VSD, and open); and
reciprocating (hermetic and open). Where water flow is variable,
performance curves are provided for pumps. These include
constant-speed/variable-flow "riding the pump curve" and electronically
commutated variable speed. For expert users, parameter values are
editable in the equations describing the performance curves for chillers
and pumps. 

 

In addition to selecting appropriate performance curves, the user is
able to specify interconnected performance inputs for capacity, COP,
condenser and chilled water temperatures, flow rates, and loop delta-T
at both rated and design conditions. An input is provided for the load
fraction below which the chiller will cycle on and off. The user also
has control of operating parameters such as condenser-water setpoint and
variation of this setpoint via a formula profile (which may reference
outdoor or indoor conditions and other sensed variables), chilled supply
water temperature (SWT), and ramped SWT reset between high and low
outdoor temperature setpoints. 

 

The cooling tower and condenser-water loop use essentially the same
cooling tower model that is provided for the waterside economizer
component in the current version of ApacheHVAC. The cooling tower model
presently includes a two-speed fan with flow fraction setting for each
speed, approach, range, and electric input ratio. This tower and
condenser-water loop model accounts for changes in outdoor conditions,
chiller heat rejection, and user-controlled tower operating parameters
as described above. 

 

Primary and secondary chilled water loops are modeled for the first
release of this new facility in a PRM-compliant "common pipe"
configuration. For this configuration, the primary loop uses a
constant-speed pump that operates whenever the chiller is running and
the secondary loop with flow controlled to maintain the specified CHW
supply temperature and loop delta-T. Either a
constant-speed/variable-flow pump riding the pump curve or a
variable-speed pump with variable speed drive (VSD) can be specified for
the secondary (chilled-water distribution) loop. Cooling coils, chilled
ceilings, etc. are then assigned to the secondary loop associated with a
particular chiller.

 

The currently available release of the VE uses a simpler model that does
provide means of describing the performance of a water-cooled chiller,
cooling tower, and pumps in relation to both part-load fraction and
outdoor wet-bulb or dry-bulb temperatures. This is presently done via a
matrix of user input data points for the chiller COP, condenser-water
pump power, cooling tower fan power, and chilled-water pump power. With
appropriate inputs, the chiller COP in this simpler exiting model can be
thus be varied according to both load fraction and outdoor conditions,
while the power for the associated pumps and fans can separately be
varied according to load fraction. However, because this simpler model
does not use the type of curves that many EnergyPlus and DOE-2 users are
accustomed to and does not explicitly model the thermodynamics of the
CW, primary CHW, and secondary CHW loops or their controls, the new
facilities described above have been developed to do just this.

 

Hopefully this helps to clarify the current and near-term capabilities
of the VE for those concerned specifically with modeling HVAC systems.

 

 

 


Timothy Moore 
Senior Consultant
Special Projects 

Office: 415 983-0603
timothy.moore at iesve.com <mailto:timothy.moore at iesve.com> 
www.iesve.com <http://www.iesve.com/> 



**Design, Simulate + Innovate with the <Virtual Environment>**

Email Disclaimer <http://www.iesve.com/disclaimer.html> 

 

 

 

 

 

 

 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Benjamin
Jordan
Sent: Thursday, March 26, 2009 12:12 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Modeling a Cooling Tower

 

Hello everyone,

   I was curious if anyone has a program or excel program that models
the fan energy and pumping energy of cooling towers. I currently use
IES-VE, which does not have any cooling tower capabilities (to my
knowledge), so I end up calculating the fan and pump energy for the
cooling towers in a crude excel sheet. Does anyone have a better way to
do this that takes into account the air WB temp, load of the building,
and size of fan? Thanks for the help!

On Thu, Mar 26, 2009 at 3:01 PM, <
bldg-sim-request at lists.onebuilding.org> wrote:

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Today's Topics:

  1. PhD position (Hensen, J.L.M.)
  2. Re: SunTools Plugin for SketchUp available (Zoeteman, Mark R.)


----------------------------------------------------------------------

Message: 1
Date: Wed, 25 Mar 2009 23:10:14 +0100
From: "Hensen, J.L.M." <j.hensen at tue.nl>
Subject: [Bldg-sim] PhD position
To: "bldg-sim at lists.onebuilding.org" <bldg-sim at lists.onebuilding.org>
Message-ID:
       <
CD91BC49A883474EAC61C23BC0F0071B01315DC02EE3 at EXCHANGE10.campus.tue.nl>

Content-Type: text/plain; charset="us-ascii"

We have a fully funded opening for a PhD researcher at Eindhoven
University of Technology.

The title of the project is "Towards E+ steel-frame industrial hall:
simulation support for objective prediction of energy in use". The aim
is to enable an objective sustainability assessment of industrial halls
and to expand building energy simulation tools with models for new
construction materials, system components and possible system
configurations to account for the industrial hall construction
specifics, process energy production and on-site electricity generation.

Further details are available at 
http://www.m2i.nl/pro1/general/start.asp?i=0&j=0&k=0&p=0&itemid=387

Please don't hesitate to contact me for further information.

I would appreciate it very much if you could pass this message to
suitable candidates.

Thanks!
Jan


prof. dr. ir. Jan L.M. Hensen | www.bwk.tue.nl/bps/hensen<
http://www.bwk.tue.nl/bps/hensen> | +31 (0)40 247 2988 | Building
Physics & Systems | Eindhoven University of Technology | P.O. Box 513 -
VRT6.18 | 5600 MB EINDHOVEN, Netherlands



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Message: 2
Date: Thu, 26 Mar 2009 14:24:17 -0400
From: "Zoeteman, Mark R." <mrzoeteman at FTCH.com>
Subject: Re: [Bldg-sim] SunTools Plugin for SketchUp available
To: "Guedi Capeluto" <arrguedi at techunix.technion.ac.il>,
       <bldg-sim at lists.onebuilding.org>
Message-ID:
       <425CE15142917C41857CF0D16D2C4D7F091821E9 at ftchex3.corp.ftch.com>
Content-Type: text/plain; charset="us-ascii"

Guedi:

This does not seem ready for real use.  We tried it and is very
simplistic and does not seem to give functionality.  It seems to do
little more than plot points in model, but not analyze model.  The
internal SketchUp tools will do more than SunTools.

Mark Zoeteman, FTC&H



From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Guedi
Capeluto
Sent: Tuesday, March 24, 2009 1:17 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] SunTools Plugin for SketchUp available



SunTools a new Plugin for SketchUp is available now.



Plug-in Features

- SunPATH: visualization (month and year)

- SunPOS: Sun Position for a date and time

- SunVIEW: Axonometric views from the Sun

- SunPENETRATION: Analyze Sun Penetration/Access in any specific
analysis point.



The plug-in can be downloaded after registration from:
http://tx.technion.ac.il/~arrguedi/SunTools/download.html



Enjoy SunTools.



Guedi Capeluto

arrguedi at technion.ac.il



Arch. Guedi Capeluto, D.Sc.
Faculty of Architecture and Town Planning
Technion - Israel Institute of Technology
Technion City,  Haifa 32000. Israel
Tel:+972.4.8294012  Fax:+972.4.8294617

email:   arrguedi at tx.technion.ac.il
web  :   http://www.technion.ac.il/~arrguedi/



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