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Re: [TRNSYS-users] Generating a control signal for a storage tank

Ali,
  I think what you are describing is just a simple thermostat in cooling mode (turn something on if a temperature rises above a certain setpoint and turn it off if the temperature falls below that setpoint). You can use Type2. If you are using Trnsys17 then there is already a Type2 proforma set up to do this in Controllers: Aquastat: Cooling Mode: Type2-AquastatC. If you have Trnsys16 you can set up Type2 to do the same. Input 2 becomes the setpoint (88C) and Input 1 will be connected from the temperature of the bottom node of your tank. The upper dead band will be 1C and the lower dead band will be -1C.

  If you have the TESS Controllers Library, you will find models of cooling aquastats in there as well.
Kind regards,
 David
 

On 2/24/2014 06:56, ali shirazi wrote:

Dear Trnsys users,


I am modeling a solar assisted absorption chiller. In this system, a hot water storage tank is used to store solar thermal energy. The cycle is also equipped with an auxiliary heater which is switched on in case the tank temperature is lower than a certain value. I need to generate a control signal (either 0 or 1) representing if the tank is on or off. The following briefly describes the intended control strategy:

The tank is on (control signal=1) if the bottom node temperature is greater than 88 C and it is deactivated (control signal value=0) in case the temperature at the top of the tank is less than 88 C. In this case, the tank could be charged while the auxiliary heater is operating.

I suppose an on/off differential controller would work for above mentioned strategy (an equation box may be needed to be used as well) but do not know how to make it work! I would really appreciate it if you could give me hand in this regard.

Looking forward to hearing from you soon.


Regards,


--
Ali shirazi
PhD Candidate
School of Mechanical and Manufacturing Engineering
The University of New South Wales
Sydney NSW 2052
Australia
Email:


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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
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d.bradley@tess-inc.com

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