[Equest-users] Curve Coefficients

[Nick Caton]

Hi John,

 

To answer your first question... For a DX cooling system, my
understanding is that COOL-EIR-FT's temperatures are the outside drybulb
(at the condenser/heatpump) and the entering wetbulb temperature at the
evaporator (mixed air conditions).  This mirrors how packaged equipment
efficiencies/capacities are presented in manufacturers' literature.  See
attached discussion for an example.

 

I understand COOL-CAP-FT and COOL-SH-FT curves work from the same
temperatures.

 

To your second question... I'm with you!  

 

I'd like to see the equation for "hourly electricity consumption" for an
air-cooled DX process written out in its entirety showing all the
affecting - I was searching for something analogous to [Volume 2:
Dictionary > HVAC Components > CHILLER > Chiller Energy Consumption] for
airside DX cooling systems a while ago and also came up empty-handed.  I
have a hunch the effects of the 3 bypass curves (which are a mystery to
me) may have something to do with the hourly calculated total capacity
and/or EIR though... perhaps those need to work their way into your
equation? 

 

Regarding the hourly results you're using to check your work... I'm not
sure whether those are the correct figures to work from, but I'd caution
to be mindful of the wonky effects of altitude on calculated
capacities/airflows when working with hourly outputs - recent discussion
on the list brought more to light on this topic - and the effects are
more pervasive than I originally thought...

 

~Nick

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Grando,
John
Sent: Wednesday, February 02, 2011 12:18 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Curve Coefficients

 

I'm basically trying to figure out how eQUEST comes up with the total
Electric consumption for a DX coil.  I thought it was the below

 

Total Capacity * Capacity Curve [T] * Total EIR * EIR Curve [T] * EIR
Curve [PLR] but it's not coming out exactly the same.  Does anyone have
any input for what I'm missing.  The attached .xls is an example for one
day.  The total capacity is 79.983 kBTU/Hr and the EIR is  0.2722.

 

 

 

John Grando LEED AP| Mechanical Engineer
Phone: 212-615-3705 | Fax: 212-615-3700
jgrando at cosentini.com

Cosentini Associates - A Tetra Tech Company
Two Pennsylvania Plaza - Third Floor - New York, NY 10121
www.cosentini.com <http://www.cosentini.com/> 

 

 

 


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From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Grando,
John
Sent: Wednesday, February 02, 2011 7:55 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Curve Coefficients

 

Hello,

 

For the curve COOL-EIR-FT the two inputs for a water loop heat pump
system are "entering wetbulb temperature" and "entering water
temperature".  I understand that the water temperature is the condenser
water, but is the entering wetbulb temperature for the evaporator side?

 

 

John Grando LEED AP| Mechanical Engineer

 

 

 


NOTICE OF CONFIDENTIALITY This E-mail message and its attachments (if
any) are intended solely for the use of the addressees hereof. In
addition, this message and the attachments (if any) may contain
information that is confidential, privileged and exempt from disclosure
under applicable law. If you are not the intended recipient of this
message, you are prohibited from reading, disclosing, reproducing,
distributing, disseminating or otherwise using this transmission.
Delivery of this message to any person other than the intended recipient
is not intended to waive any right or privilege. If you have received
this message in error, please promptly notify the sender by reply E-mail
and immediately delete this message from your system. 

 

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