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

Enyuan Hu bearcharge at gmail.com
Fri Nov 21 10:26:13 PST 2014


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 at lists.onebuilding.org> wrote:

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>    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 at tess-inc.com)
>    4. Re: (no subject) (Jason Glazer)
>
>
> ---------- Forwarded message ----------
> From: David BRADLEY <d.bradley at tess-inc.com>
> To: "TRNSYS users mailing list at OneBuilding.org" <
> trnsys-users at lists.onebuilding.org>, trnsys-users <
> trnsys-users at 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
>
>
> _______________________________________________
> TRNSYS-users mailing listTRNSYS-users at lists.onebuilding.orghttp://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:+1.608.278.1475d.bradley at tess-inc.com
> http://www.tess-inc.comhttp://www.trnsys.com
>
>
>
> ---------- Forwarded message ----------
> From: "haydar kepekçi" <haydar389 at gmail.com>
> To: "TRNSYS users mailing list at OneBuilding.org" <
> trnsys-users at 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
> <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 at 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 at 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 at lists.onebuilding.org
> > http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at lists.onebuilding.org
> http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
>
>
>
> ---------- Forwarded message ----------
> From: mcdowell at tess-inc.com
> To: "TRNSYS users mailing list at OneBuilding.org" <
> trnsys-users at 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 53703608-274-2577
>
>  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
> <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 at 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 at 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 at lists.onebuilding.org
> > http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at lists.onebuilding.org
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>
> _______________________________________________
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>
>
>
> ---------- Forwarded message ----------
> From: Jason Glazer <jglazer at gard.com>
> To: trnsys-users at 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 at 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 at gmail.com <mailto:bheymer at 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 at 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 at lists.onebuilding.org
>>      >
>>     http://lists.onebuilding.org/listinfo.cgi/trnsys-users-
>> onebuilding.org
>>
>>     _______________________________________________
>>     TRNSYS-users mailing list
>>     TRNSYS-users at lists.onebuilding.org
>>     http://lists.onebuilding.org/listinfo.cgi/trnsys-users-
>> onebuilding.org
>>
>>
>>
>>
>> _______________________________________________
>> TRNSYS-users mailing list
>> TRNSYS-users at lists.onebuilding.org
>> http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
>>
>>
> --
> Jason Glazer, P.E., GARD Analytics, 90.1 ECB chair
> Admin for onebuilding.org building performance mailing lists
>
>
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