[TRNSYS-users] Cooling demand in TRNSYS

Fri May 14 08:59:03 PDT 2021

José Javier,

   Sorry for the delay in getting back to you. Is the problem specific 
to one particular fourth air node? In other words, does it all work so 
long as you have three zones (no matter which three zones they are) and 
everything turns to zero when you add the fourth zone? Or is there 
something strange about one particular zone (which happens to be the 
fourth one that you are adding)?

   In a way, two concepts are getting mixed up here. Your building is 
operating in "energy rate control" in which it is calculating a load, an 
energy removal rate that must be provided by the cooling coil. The 
cooling coil's energy removal rate should not be passed back to the 
building though because if it is then the load changes. The cooling coil 
is intended to operate in "temperature level control" in which you turn 
off the load calculation in the building and allow its temperature to 
float. You then define a thermostat and some combination of coils, 
plenums, pumps, and fans, which act together to maintain the building's 
temperature as close to the setpoint as possible.

   I would recommend that you switch off the idealized COOLING (and 
HEATING) types in TRNBuild and instead define a VENTILATION for each of 
your zones. Then, instead of passing the air side heat transfer from the 
cooling coil to the building, you'll pass the outlet air conditions from 
the coil to those VENTILATIONs. A thermostat model will be needed in 
order to command the fan and pump that move air and liquid across the 
cooling coil.

kind regards,

  David

On 05/12/2021 02:52, RUBIO RUBIO, JOSÉ JAVIER wrote:
>
> David,
>
> Thank you for your answer. I see your point but what doesn’t make 
> sense to me is the fact that I have four airnodes with different 
> cooling setpoints. When I use the Air Side Heat Transfer output from 
> the cooling coils (Type508) as an input for the cooling power 
> available in three of the airnodes, it works and Qcool is not zero in 
> any of them but it becomes zero (all of them) when I include the 
> fourth airnode.
>
> I have used a plot to compare the Qcool from Type56 and the Air Side 
> Heat Transfer output from the cooling coils and the difference among 
> the airnodes is that in the three which work, as I mentioned in the 
> previous paragraph, the output from the cooling coil is bigger than 
> Qcool from Type56. However, in the fourth airnode is just the opposite.
>
> I hope I have explained myself clearly and you can help me to figure 
> it out.
>
> Thanks again in advance and sorry for the inconvenience,
>
> Best regards,
>
> José Javier.
>
> *De:*David BRADLEY <d.bradley at tess-inc.com>
> *Enviado el:* lunes, 10 de mayo de 2021 19:50
> *Para:* TRNSYS users mailing list at OneBuilding.org 
> <trnsys-users at lists.onebuilding.org>
> *CC:* RUBIO RUBIO, JOSÉ JAVIER <josejavier.rubio at edu.upct.es>
> *Asunto:* Re: [TRNSYS-users] Cooling demand in TRNSYS
>
> José Javier,
>
>   What Type56 is reporting in those outputs is the amount of 
> additional energy that must be removed from a zone in order to 
> maintain the setpoint that you have provided. If you give the zone 
> exactly the amount of cooling energy that it needs then the demand for 
> additional cooling energy is zero.
>
>   kind regards,
>
>  David
>
> On 05/07/2021 07:52, RUBIO RUBIO, JOSÉ JAVIER via TRNSYS-users wrote:
>
>     To whom it may concern,
>
>     I am developing a cooling system with TRNSYS18 and I have several
>     problems when I try to connect as an input the heat transfer of
>     the coils in the chambers by using the Cooling Type Manager. You
>     have an example below:
>
>     Where Q_evap4C, Q_evap8C, Q_carga4C and Q_descarga4C are the “Air
>     Side Heat Transfer” output of the cooling coils.
>
>     When I use it as an input for the power available in each cooling
>     zone, the cooling demand of the zone is zero which is non-sense.
>     Any way to figure it out?
>
>     Thanks in advance and sorry for the inconvenience,
>
>     Best regards.
>
>     Jose Javier.
>
>
>
>     _______________________________________________
>
>     TRNSYS-users mailing list
>
>     TRNSYS-users at lists.onebuilding.org  <mailto:TRNSYS-users at lists.onebuilding.org>
>
>     http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org  <http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org>
>
> -- 
> ***************************
> David BRADLEY
> Principal
> Thermal Energy Systems Specialists, LLC
> 3 North Pinckney Street - suite 202
> Madison, WI  53703 USA
> P:+1.608.274.2577
> d.bradley at tess-inc.com  <mailto:d.bradley at tess-inc.com>
> http://www.tess-inc.com  <http://www.tess-inc.com>
> http://www.trnsys.com  <http://www.trnsys.com>

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI  53703 USA

P:+1.608.274.2577
d.bradley at tess-inc.com

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

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