[Equest-users] Flat part load curve for Chiller

Brian Fountain bfountain at greensim.com
Fri Jul 8 07:46:02 PDT 2011


As Praveen pointed out --

setting a = 1 means the compressor will draw full power regardless of 
the part load.

setting b = 1 and a = 0 means the the compressor COP will be the full 
load value for all part load conditions. (slope = 1)

On 7/8/2011 9:52 AM, Nick Caton wrote:
>
> Sambhav and Praveen:
>
> Recently I see both of you were asking about "flat" curves or curves 
> that would always return the same value (1.0) to be multiplied against 
> the modified input (EIR).
>
> Trying to do this in the raw data method might be possible, but it 
> might not be either... the math involved in those regressions is 
> something I can only briefly comprehend in short bursts =).
>
> What I can offer is -- this sounds pretty simple if you define the 
> coefficients directly instead!
>
> For example:
>
> Bi-Quadratic:  Z = a + bX + cX^2 + dY + eY^2 + fXY
>
> If you want the value returned to always equal 1.0, just choose 
> coefficients that make the variables X and Y not matter!
>
> [b = c = d= e = f = 0], and set [a =1].
>
> Does that help?
>
> ~Nick
>
> cid:489575314 at 22072009-0ABB**
>
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>
> *NICK CATON, P.E.***
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> -----Original Message-----
> From: equest-users-bounces at lists.onebuilding.org 
> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of 
> sambhav tiwari
> Sent: Thursday, July 07, 2011 11:43 PM
> To: equest-users at lists.onebuilding.org
> Subject: [Equest-users] Curve fitting
>
> Hi All,
>
>             Each time i create a new curve by putting same values of
>
> raw data i am getting different values of coefficients a,d,c,d for
>
> cubic equation(a+bx+cx2+dx3) the solution (a,b,c,d) should be same
>
> only if raw data values are same in each curve then why
>
> coefficient(a,b,c,d) values are changing?
>
> Thanks
>
> Sambhav
>
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> *From:*equest-users-bounces at lists.onebuilding.org 
> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Praveen Jain
> *Sent:* Monday, July 04, 2011 11:41 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Flat part load curve for Chiller
>
> Dear All
>
> For our district cooling project, we require flat part load curve for 
> the air cooled screw chiller.
>
> I played  with curve coefficient in two ways
>
> (1)  A=1, B=0, C=0
> With this, Ratio of cooling energy from SS-D and BEPU, is not giving 
> entered COP.
>
> (2) A=0, B=1 , C=0
>
> With this, Ratio of cooling energy from SS-D and BEPU, is giving 
> approx entered COP.
>
>
> What is exact way to create flat part load curve in eQuest.
> -- 
> With Thanks and Regards,
> Praveen K. Jain
> Roorkee
>
>
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