[TRNSYS-users] Type743’s power coefficients parameter setting

Alastair McDowell alastair.mcdowell at energyae.com
Tue Nov 17 02:30:02 PST 2015

Hi Weiwei,

I had a look at your fitting equation and TRNSYS project.

Firstly, you can adequately describe that data with a 2-parameter (linear) curve. The R^2 value does not improve by adding the third parameter. That will simplify things a bit.

Second, your power coefficients are not quite right. In your excel spreadsheet, you haven't divided your power drawn by the pump by the nominal/rated power that corresponds to the rated mass flow rate of the pump. The power coefficients (a0,a1...) relate to the relationship between P/P_rated and m/m_rated. Your coefficients should be more in the order of 0.4.

The error in your TRNSYS project is you have connected the outlet fluid temperature of the pump to the equation, instead of power consumption. Once you fix that, the power output should come out right, in the range 15-20kW.

Kind regards,

Alastair McDowell
Engineering Consultant
Energy Analysis & Engineering – Enabling innovation for a sustainable future
T: +61 450 600 842
E: alastair.mcdowell at energyae.com
608 Harris St Sydney NSW 2007 Australia | http://www.energyae.com<http://www.energyae.com/>

From: TRNSYS-users <trnsys-users-bounces at lists.onebuilding.org> on behalf of ???v v <xiaoweiweiwu at hotmail.com>
Sent: Tuesday, 17 November 2015 8:51 PM
To: trnsys-users at lists.onebuilding.org
Subject: Re: [TRNSYS-users] Type743’s power coefficients parameter setting

Dear Alastair,
Thank you for your patient reply. Now I can understand the relationship between the coefficients and the parameters. And, I tried to understood the Fortran code although my poor knowledge about it.
But it sees that the pump’s power drawn result is not right according to the setting as the following, Which is much lower than the equation curve I have attached the simple project(.tpf and.txt file) and the fitting equation(.xls) data file.

For example, I has fitted a pump power curve equation as followings
p = 56877 + 49714(m/m rated) + 1094.3(m/m rated) ^2  (R² = 0.9959), So the setting is :

power coefficient-1 = a0=56877 (Parameter 6 for TYPE 743)

power coefficient-2 = a1=49714 (Parameter 7 for TYPE 743)

power coefficient-3 = a2=1094.3(Parameter 8 for TYPE 743)

 May you tell me the reason? Thank you very much for your time!
with best regards

yours sincerely
Chongqing University

From: xiaoweiweiwu at hotmail.com
To: trnsys-users at lists.onebuilding.org
Subject: Type743’s power coefficients parameter setting
Date: Mon, 16 Nov 2015 13:49:52 +0800

Dear all,
In the type743’s document, there is an equation743.1 about P, which is power drawn the pump, as following:
P=a0+a1(m/mrated)+ a2(m/mrated)2+ a3(m/mrated)3+………..
In the type743’s parameter setting, parameter number 5 is set to“number of power coefficients”,if I input “3”then the parameter number6?7 ?8 is as following:
power coefficient-1
power coefficient-2
power coefficient-3
And the explanation about the coefficient is “The value of the polynomial multiplier for the relationship between normalized pump power and normalized pump flow rate”.
My question is:
1)whether a1?a2 a3 is correspond to power coefficient-1?power coefficient-2 and power coefficient-3 respectively? if yes, how to set the value a0? or i just need fitting an equation that a0 is zero?
2)If not ,what is the right relationship between them?
In addition, I referred to an example named “pumps with flow rate known” in Tess models of TRNSYS software, the type743’s parameter 5 is set to 3, and the parameter6 and 7 (power coefficient-1?power coefficient-2) are  both  0, while parameter 8 is set to 1. The similar situation setting could be found in other types such as TYPE510’s power coefficient.
Thank you very much help me out of this issue.

With best regards

Yours sinscerely

Chongqing university

Thank you very much help me out of this issue.
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