[TRNSYS-users] estimating the temperature of a sensible heat storage by using the temperature of the previous timestep

[David BRADLEY]

Johannes,
   Your formula looks right except that I don't think the first 
Tst,previous term on the right hand side should be divided by the 
Cp,st*m,st.

   You can get the temperature at the previous time step by using either 
Type661 from the TESS Libraries or Type93. Both hold on to output values 
for a user-specified number of timesteps before releasing them.

   I am not entirely clear why you don't want to use an actual storage 
media model such as Type10, which solves the coupled differential 
equations that allow you to model stratified storage and also take care 
of computing the state of the air leaving the storage media so that it 
can be correctly passed either back to the collector or on to something 
else.

Best,
  david


On 5/18/2012 04:45, Johannes Schütz wrote:
> Hello Trnsys-users,
>
> first of all I have to admit, that I'm quite new to Trnsys Studio. So 
> the question might be really easy to answer. I would
> be really glad, if you can help me.
>
> My problem is the following:
>
> I have linked a solar air collector to an equation, which is supposed 
> to simulate the sensible storage in a very simplified way.
> I assume, that the temperature of the hot air from the collector is 
> constant, also the volume flow and further I assume, that the
> heat transfer between the hot air and the heat storage is ideal. That 
> means, that the air is released from the storage at storage
> temperature. Last not least I assume that there are no heat lossses to 
> the ambience.
>
> Taking all the assumptions above, an estimation of the storage 
> temperature for each timestep shouldn't be difficult.
> I would propose the following formula:
>
>
>
> The only problem I face, how to command Trnsys to use the Storage 
> tempearture Tst from the
> previous timestep. Hopefully you can help me solving my problem.
>
> Thanks for your help in advance.
>
> Take care
>
> Jojo
>
>
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> TRNSYS-users at cae.wisc.edu
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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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