[TRNSYS-users] Type 2b controller dead band problem.
David BRADLEY
d.bradley at tess-inc.com
Fri Sep 23 10:01:18 PDT 2011
Mike,
I think your simulation is correct (nice job, incidentally, in
setting it up). I think the "problem" is that your collector is just too
small to collect enough energy to add to the tank. As a result, whenever
there is flow through the collector, the temperature rise is so small
that the outlet temperature basically equals the inlet temperature and
the controller decides to turn off. Imagine the limit; if you had a
collector that had zero area, it couldn't collect any energy; it would
just a pipe of water sitting in the sun. When there is no flow, the pipe
heats up, the water gets hot, and the controller decides to turn on the
pump. However, as soon as the flow starts, the water comes back to the
tank at the same temperature with which it left. I doubled the area of
your collector and suddenly it all went stable.
I did clean up the connections between the weather processor and the
collector; there are a few more solar radiation connections that need to
be made (diffuse solar, incidence angle, etc.). You also need to use
Type69 to get the sky temperature. Alternatively (and much preferably)
you should change Type109 for Type15; Type15 also reads TMY2/Meteonorm
data files but has a number of advantages over Type109 (including
calculating the effective sky temperature internally and outputting the
wind speed.
Regards,
David
On 9/22/2011 15:50, Michael Bissett wrote:
> I have taken your advice and made the timestep, 0.125hr
>
> Still I cannot get it to work. it is still switching on the time step
> instead of the dead-band temp.
>
> Mike
>
> On Wed, Sep 21, 2011 at 3:33 PM, Matt Duffy <duffy at tess-inc.com
> <mailto:duffy at tess-inc.com>> wrote:
>
>
> Dear Michael,
>
> Please make sure that you are using a reasonable timestep such as
> 0.125 hr (type in terms of hours to avoid problems with the
> Studio's minute conversion trucation). Also, make sure that you
> have the latest TRNSYS and TESS Libraries versions as well.
>
> Best regards,
>
> Matt Duffy
>
> *----- Original Message -----*
> *From:* "Michael Bissett" <mikebiscuit at gmail.com
> <mailto:mikebiscuit at gmail.com>>
> *Sent:* Tue, September 20, 2011 12:44
> *Subject:* Re: [TRNSYS-users] Type 2b controller dead band problem.
>
> Hi
> I have read the information, I have tried to increase parameter 1,
> I have also looped the controller to its self. Still it does not work
> I have also tried changing many other parameters and have spent a
> lot of time on this problem. still with no luck.
> Any other suggestions?
> Mike
>
> On Tue, Sep 20, 2011 at 1:59 PM, Angel Carrera
> <angel.carrera at aiguasol.coop <mailto:angel.carrera at aiguasol.coop>>
> wrote:
>
>
> Mike,
>
> you should connect the output control function of the
> controller to its own input control function (Input number 4).
> Also, you should increase the value of parameter 1, to the
> default value at least (the influence of this parameter is
> explained at the type 2 documentation, I recommend you to read
> it, together with the generic section for controllers at the
> trnsys help)
>
> Regards
>
> Angel
>
>
> 2011/9/19 Michael Bissett <mikebiscuit at gmail.com
> <mailto:mikebiscuit at gmail.com>>
>
> Dear Trnsys
> I am experiencing problems with a simple*type 2b controller*.
> I am using a solar collector type 564b
> I am trying to compare the temperature of the output of
> the collector with output of the tank, getting a
> temperature difference. I have set the dead band from 4-10
> degrees C.
> In the simulation as the temperature rises to 10degrees
> difference, the control signal is 1 switching the pump on
> correctly. but after this the controller only switches
> every time step. I have tried shortening the time step...
> and changing other parameters.. still with no success.
> I have attached the file.
> Yours Sincerely
> Mike Bissett
> Department of Electrical Engineering
> University of Cape Town
> South Africa
> _______________________________________________
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>
>
>
> --
> *Àngel Carrera*
>
> *Responsable I+D
> Àrea tècnica*
>
> Sistemes Avançats d'Energia Solar Tèrmica SCCL
> C/ Roger de Llúria, 29 3r 2a 08009 Barcelona
> Tel: (+34) 93 342 47 55 <tel:%28%2B34%29%2093%20342%2047%2055>
> Fax: (+34) 93 342 47 56 <tel:%28%2B34%29%2093%20342%2047%2056>
>
> angel.carrera at aiguasol.coop <mailto:angel.carrera at aiguasol.coop>
> http://www.aiguasol.coop <http://www.aiguasol.coop/>
>
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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 at tess-inc.com
http://www.tess-inc.com
http://www.trnsys.com
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