Question: Modeling Specific Chillers

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I think I am hitting a roadblock here, trying to get the necessary data to
model the chillers. I have gone through the EDR document on simulating HVAC
systems and other posts on modeling chillers here on the mailing list. I
think I can get the part load data from the manufacturer.

Trying to get the full load data has been difficult though. The chiller
manufacturer tells me that if I want the full load capacity at reduced
condenser entering and/or higher evaporator leaving temperatures, he can
only provide up to about 5% higher capacity than design capacity. Beyond
this he will need to change the expansion device in his selection software
to get the total capacity. I don't believe changing the expansion device is
the right way to go.

I have attached a sample data sheet with various data points that I thought
I should get from the manufacturers. The data points I have in the sheet
are what will be practically seen in operation here. However they are all
lower than the design temperatures of the chiller. I'm not sure if I am
going in the right direction with this one.

Any inputs are appreciated.

Thanks,

Sunil Nair

Sunil Nair's picture
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Joined: 2012-11-22
Reputation: 200

Hello Sunil,
It sounds like the manufacturer may be trying to get you a capacity for a given set of condenser and evaporator temperatures. What you need is the manufacturer to tell you what the full load (and part load) capacities of the machine are with the lift conditions you specified. So, for higher lift conditions, the machine will have lower capacities. He doesn?t need to match the capacity you selected the chiller at to all the lift conditions you specify.

If it helps, the spreadsheet I use to generate custom chiller curves can be downloaded from here:
http://www.esimforums.com/equest/viewtopic.php?f=13&t=116&start=0&view=viewpoll

Cheers,
Jeremy

Jeremy McClanathan's picture
Joined: 2011-09-30
Reputation: 200

In general, there is also a database of chiller curves that is provided for energyplus that I believe are also valie for eQuest if you convert them into Fahrenheit temperatures. If the one in questions happens to be on that list it could be helpful.

http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_Chillers_Data_ElectricEIR.html

Brendan Hall

Hall, Brendan's picture
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Joined: 2011-09-30
Reputation: 1

As a word of caution, I tried going down that road before and ended up not being able to use the E+ curves. The parameters from a bi-quadratic equation in metric units cannot be used in eQuest. As Brendan mentioned, you would have to convert to Fahrenheit. I would imagine this would require backing out the parameters necessary to construct a curve from the metric equations, converting to US units, then reconstructing a curve. I don?t know this for a fact though.
Cheers,
Jeremy

Jeremy McClanathan's picture
Joined: 2011-09-30
Reputation: 200

I suggest taking a look at the Taylor Engineering website, they used to
have an excel sheet with a considerable amount of VBA code in the back end
that generated the DOE coefficients for constant speed, variable speed and
chiller systems that utilize variable condenser water flow rate (requires
equation to be solved for Cwrt not Cwst).

Regards Phiip

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*From:* equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Jeremy
McClanathan
*Sent:* September-19-13 1:32 PM
*To:* 'Hall, Brendan'; 'Sunil Nair'; 'David Eldridge'
*Cc:* 'equest-users at lists.onebuilding.org'
*Subject:* Re: [Equest-users] Question: Modeling Specific Chillers

As a word of caution, I tried going down that road before and ended up not
being able to use the E+ curves. The parameters from a bi-quadratic
equation in metric units cannot be used in eQuest. As Brendan mentioned,
you would have to convert to Fahrenheit. I would imagine this would
require backing out the parameters necessary to construct a curve from the
metric equations, converting to US units, then reconstructing a curve. I
don?t know this for a fact though.

Cheers,

Jeremy

*From:* Hall, Brendan [mailto:BHall at karpinskieng.com]
*Sent:* Thursday, September 19, 2013 10:14 AM
*To:* Jeremy McClanathan; 'Sunil Nair'; 'David Eldridge'
*Cc:* 'equest-users at lists.onebuilding.org'
*Subject:* RE: [Equest-users] Question: Modeling Specific Chillers

In general, there is also a database of chiller curves that is provided for
energyplus that I believe are also valie for eQuest if you convert them
into Fahrenheit temperatures. If the one in questions happens to be on that
list it could be helpful.

http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_Chillers_Data_ElectricEIR.html

Brendan Hall

*From:* equest-users-bounces at lists.onebuilding.org [
mailto:equest-users-bounces at lists.onebuilding.org]
*On Behalf Of *Jeremy McClanathan
*Sent:* Thursday, September 19, 2013 12:58 PM
*To:* 'Sunil Nair'; 'David Eldridge'
*Cc:* 'equest-users at lists.onebuilding.org'
*Subject:* Re: [Equest-users] Question: Modeling Specific Chillers

Hello Sunil,

It sounds like the manufacturer may be trying to get you a capacity for a
given set of condenser and evaporator temperatures. What you need is the
manufacturer to tell you what the full load (and part load) capacities of
the machine are with the lift conditions you specified. So, for higher
lift conditions, the machine will have lower capacities. He doesn?t need
to match the capacity you selected the chiller at to all the lift
conditions you specify.

If it helps, the spreadsheet I use to generate custom chiller curves can be
downloaded from here:

*
http://www.esimforums.com/equest/viewtopic.php?f=13&t=116&start=0&view=viewpoll
*

Cheers,

Jeremy

*From:* Sunil Nair
[mailto:energymodel.sunil at gmail.com]

*Sent:* Wednesday, September 18, 2013 9:55 PM
*To:* David Eldridge
*Cc:* equest-users at lists.onebuilding.org
*Subject:* Re: [Equest-users] Question: Modeling Specific Chillers

I think I am hitting a roadblock here, trying to get the necessary data to
model the chillers. I have gone through the EDR document on simulating HVAC
systems and other posts on modeling chillers here on the mailing list. I
think I can get the part load data from the manufacturer.

Trying to get the full load data has been difficult though. The chiller
manufacturer tells me that if I want the full load capacity at reduced
condenser entering and/or higher evaporator leaving temperatures, he can
only provide up to about 5% higher capacity than design capacity. Beyond
this he will need to change the expansion device in his selection software
to get the total capacity. I don't believe changing the expansion device is
the right way to go.

I have attached a sample data sheet with various data points that I thought
I should get from the manufacturers. The data points I have in the sheet
are what will be practically seen in operation here. However they are all
lower than the design temperatures of the chiller. I'm not sure if I am
going in the right direction with this one.

Any inputs are appreciated.

Thanks,

Sunil Nair

Philip Kennedy's picture
Offline
Joined: 2013-08-09
Reputation: 0