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Re: [TRNSYS-users] TRNSYS-users Digest, Vol 119, Issue 19

Enyuan,

1. That is correct.

2. There is a lot of information in the data file. The file that you excerpted below is the heating performance data file and it says that the performance metrics are valid for return air temperatures (actually mixed return + outdoor air temperatures) between 15.6 and 26.7C and for outdoor temperatures between -19.4 and 22.2C. If you look at the cooling performance data file you will find a line near the top of the file that has the comment "outdoor dry bulb" (or something like that). If you look at the minimum and maximum value on that line you will find the range of temperatures over which the cooling performance data is valid.
Regards,
 David


On 11/21/2014 12:26, Enyuan Hu wrote:
Dear David,

As always, thank you so much for the informative answers. I'm trying to confirm if I understood correctly.

1. "...It is computed as the mass flow rate of air multiplied by the difference between the enthalpy of air leaving the heat pump and the enthalpy of the mixed air (return + ambient) entering the evaporator"..."It could be that your heat pump is cooling because there is no ambient air being mixed in and the heat pump is working only with return air..." 
so, as long as the enthalpy of entering air is larger than that of the leaving air, cooling rate will computed as positive, right? and this could happen even during the winter. One possibility is that there is no ambient air entering the heat pump and the entering air (only containing returned air) is even hotter than the leaving air, right?

2. "...Performance is interpolated within the range of data given in the file but it is not extrapolated beyond the range..."
I checked the external file and found something like:

0.875 1.000 1.042 !Normalized air flow rate
15.56 21.11 23.89 26.67 !Return air dry bulb temperature (C)
-19.44 -16.67 -13.89 -11.11 -8.33 -5.56 -2.78 0 2.78 5.56 8.33 11.11 13.89 16.67 19.44 22.22 !Outdoor dry bulb temperature (C)
1.0000 1.0000
1.1707 1.0597
...

I was wondering what kind of information we can learn from this file, especially in terms of the temperature range that gives valid computation like what you mentioned? Thanks!

best regards,
Enyuan

On Thu, Nov 20, 2014 at 12:59 PM, <trnsys-users-request@lists.onebuilding.org> wrote:
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Today's Topics:

   1. Re: total heating rate and total cooling rate in heat pump
      954 (David BRADLEY)
   2. Re: (no subject) (haydar =?UTF-8?Q?kepek=C3=A7i?=)
   3. Re: (no subject) (mcdowell@tess-inc.com)
   4. Re: (no subject) (Jason Glazer)


---------- Forwarded message ----------
From: David BRADLEY <d.bradley@tess-inc.com>
To: "TRNSYS users mailing list at OneBuilding.org" <trnsys-users@lists.onebuilding.org>, trnsys-users <trnsys-users@cae.wisc.edu>
Cc: 
Date: Thu, 20 Nov 2014 09:59:49 -0600
Subject: Re: [TRNSYS-users] total heating rate and total cooling rate in heat pump 954
Enyuan,
  The total cooling rate is the sensible and latent energy being removed from the air stream by the active section of the heat pump. It is computed as the mass flow rate of air multiplied by the difference between the enthalpy of air leaving the heat pump and the enthalpy of the mixed air (return + ambient) entering the evaporator. The heat pump does not have any kind of economizer controls built into it. The amount of outdoor air being mixed with return air is simply a function of how you have set the outdoor air damper position input. It could be that your heat pump is cooling because there is no ambient air being mixed in and the heat pump is working only with return air. If your concern is that the heat pump would not operate when the ambient temperature is so low (because of freeze up in the condenser) then you have to be careful of your external data file. Performance is interpolated within the range of data given in the file but it is not extrapolated beyond the range. If the heat pump asks for cooling (because of the way you have set the cooling signal input and fan control signal) then the performance (cooling capacity and COP) will be returned for the closest ambient temperature found in the data file.
Regards,
 David


On 11/19/2014 14:26, Enyuan Hu wrote:
Dear all,

When I'm using a type 954 air-to-air heat pump to condition a one zone building, I found that even during the winter (ambient temperature is below the cooling threshold), the 'total cooling rate' output from the heat pump is positive instead of being zero as expected. Can anyone help me explain why? Thanks!

best regards,
Enyuan Hu


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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley@tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com


---------- Forwarded message ----------
From: "haydar kepekçi" <haydar389@gmail.com>
To: "TRNSYS users mailing list at OneBuilding.org" <trnsys-users@lists.onebuilding.org>
Cc: 
Date: Thu, 20 Nov 2014 17:23:16 +0200
Subject: Re: [TRNSYS-users] (no subject)

Dont send me e- mail !! I dont want to see ur words about Fucking trnsys !!!

Sent using CloudMagic


On Per, Kas 20, 2014 at 4:32 PM, Ben Heymer <bheymer@gmail.com> wrote:

You should look through your "Result" file for the source of the error.

A common cause of errors of this type is convergence. Make sure you
have enough volume in your water loop for at least 1 timestep of water
flow. Sometimes it's also helpful to connect the mass flow output of
the pump right back to the mass flow input.

As a last resort, you can relax the convergence parameters and error
thresholds in the control cards.

Ben Heymer, PE

On Thu, Nov 20, 2014 at 3:52 AM, Michael Stochniol
<stochnio@mail.hs-ulm.de> wrote:
> Hallo everyone,
>
> im trying to create a control function using equations with logic operators for the control of a variable speed pump, in order to adjust the massflow trough the pump. I wrote a control funktion and plotted it without connecting it to the pump and it seemed to work right. But if i am conecting it to the pump my simulation freezes after around 700 timesteps or less. I am trying to create solar domestic hot water system. The question is, is it possible to create this kind of control circuit with equations ? I have similar problems with every control loop i am trying to create this way. The math should work but implemented  in TRNSYS (TRNSYS 17) the simulation stick somewhere.
>
> I am no experienced user so maybe someone could give my some advise how to implement this kind of control functions right?
>
> i am very grateful for any help or ideas.
>
> thanks in advance
>
> Michael Stochniol
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users@lists.onebuilding.org
> http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@lists.onebuilding.org
http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org



---------- Forwarded message ----------
From: mcdowell@tess-inc.com
To: "TRNSYS users mailing list at OneBuilding.org" <trnsys-users@lists.onebuilding.org>
Cc: 
Date: Thu, 20 Nov 2014 11:57:52 -0600
Subject: Re: [TRNSYS-users] (no subject)

Haydar Kepekci -

Please use the links at the bottom of the email to unsubscribe from the TRNSYS mailing list.

And please avoid using offensive language in email messages.

Regards,

Tim

 

---
Timothy P. McDowell
Executive Vice President
Thermal Energy System Specialists, LLC
22 N Carroll St, Suite 370
Madison, WI 53703
608-274-2577

On 2014-11-20 09:23, haydar kepekçi wrote:

Dont send me e- mail !! I dont want to see ur words about Fucking trnsys !!!

Sent using CloudMagic


On Per, Kas 20, 2014 at 4:32 PM, Ben Heymer <bheymer@gmail.com> wrote:

You should look through your "Result" file for the source of the error.

A common cause of errors of this type is convergence. Make sure you
have enough volume in your water loop for at least 1 timestep of water
flow. Sometimes it's also helpful to connect the mass flow output of
the pump right back to the mass flow input.

As a last resort, you can relax the convergence parameters and error
thresholds in the control cards.

Ben Heymer, PE

On Thu, Nov 20, 2014 at 3:52 AM, Michael Stochniol
<stochnio@mail.hs-ulm.de> wrote:
> Hallo everyone,
>
> im trying to create a control function using equations with logic operators for the control of a variable speed pump, in order to adjust the massflow trough the pump. I wrote a control funktion and plotted it without connecting it to the pump and it seemed to work right. But if i am conecting it to the pump my simulation freezes after around 700 timesteps or less. I am trying to create solar domestic hot water system. The question is, is it possible to create this kind of control circuit with equations ? I have similar problems with every control loop i am trying to create this way. The math should work but implemented  in TRNSYS (TRNSYS 17) the simulation stick somewhere.
>
> I am no experienced user so maybe someone could give my some advise how to implement this kind of control functions right?
>
> i am very grateful for any help or ideas.
>
> thanks in advance
>
> Michael Stochniol
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users@lists.onebuilding.org
> http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
_______________________________________________
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TRNSYS-users@lists.onebuilding.org
http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org 


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---------- Forwarded message ----------
From: Jason Glazer <jglazer@gard.com>
To: trnsys-users@lists.onebuilding.org
Cc: 
Date: Thu, 20 Nov 2014 11:59:19 -0600
Subject: Re: [TRNSYS-users] (no subject)
As a reminder, to unsubscribe just send a blank email to:

trnsys-users-unsubscribe@onebuilding.org

Jason

On 11/20/2014 9:23 AM, haydar kepekçi wrote:
Dont send me e- mail !! I dont want to see ur words about
 trnsys !!!

Sent using CloudMagic
<https://cloudmagic.com/k/d/mailapp?ct=pa&cv=5.1.6.5&pv=4.3>


On Per, Kas 20, 2014 at 4:32 PM, Ben Heymer
<bheymer@gmail.com <mailto:bheymer@gmail.com>> wrote:

    You should look through your "Result" file for the
    source of the error.

    A common cause of errors of this type is convergence.
    Make sure you
    have enough volume in your water loop for at least 1
    timestep of water
    flow. Sometimes it's also helpful to connect the mass
    flow output of
    the pump right back to the mass flow input.

    As a last resort, you can relax the convergence
    parameters and error
    thresholds in the control cards.

    Ben Heymer, PE

    On Thu, Nov 20, 2014 at 3:52 AM, Michael Stochniol
    <stochnio@mail.hs-ulm.de> wrote:
     > Hallo everyone,
     >
     > im trying to create a control function using
    equations with logic operators for the control of a
    variable speed pump, in order to adjust the massflow
    trough the pump. I wrote a control funktion and plotted
    it without connecting it to the pump and it seemed to
    work right. But if i am conecting it to the pump my
    simulation freezes after around 700 timesteps or less. I
    am trying to create solar domestic hot water system. The
    question is, is it possible to create this kind of
    control circuit with equations ? I have similar problems
    with every control loop i am trying to create this way.
    The math should work but implemented  in TRNSYS (TRNSYS
    17) the simulation stick somewhere.
     >
     > I am no experienced user so maybe someone could give
    my some advise how to implement this kind of control
    functions right?
     >
     > i am very grateful for any help or ideas.
     >
     > thanks in advance
     >
     > Michael Stochniol
     > _______________________________________________
     > TRNSYS-users mailing list
     > TRNSYS-users@lists.onebuilding.org
     >
    http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org

    _______________________________________________
    TRNSYS-users mailing list
    TRNSYS-users@lists.onebuilding.org
    http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org




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--
Jason Glazer, P.E., GARD Analytics, 90.1 ECB chair
Admin for onebuilding.org building performance mailing lists


_______________________________________________
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TRNSYS-users@lists.onebuilding.org
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_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@lists.onebuilding.org
http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org


-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley@tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com