Re: [TRNSYS-users] tank and glycol.

[David BRADLEY <d.bradley@tess-inc.com>]

Dear Fernando,
  I have had some troubles with the stability of the Type60 heat exchanger model too. I think that the algorithm for the natural convection heat transfer coefficient on the outside of the exchanger is at fault. One workaround would be to use Type534 from the TESS Storage Tank library in place of Type60 if you have access to it. You might also try changing the Type60 internal time step. Lastly, check carefully over your tank and heat exchanger configuration to make sure that they are correct. Putting a very big heat exchanger into a small tank can cause the kind of instability in calculating the heat exchanger UA.

  The answer to your question about freezing depends on the component. Some components may deal with freezing phenomena while others do not. None of the solar water heating components in the standard TRNSYS library account for freezing of the working fluid. Having done some research work on it, I can tell you that it is enormously difficult to predict when freezing will become a problem because it has almost everything to do with how the system is installed, not how the system is designed.
Best,
 David


On 11/12/2010 09:59, Sancho,Fernando wrote:

 Dear Trnsys-users,

 

Im using Type 60 as a Tank  and have a convergence problem with the solar heat exchanger just when I use glycol in it.

 

error non convergences for Hx 1. Final UAHx value = 345.adjfhadgfg

 

That is a reported problem in the list, the solutions indicated were normally  about "adding pipes in the solar loops", to be sure that   in a certain time step  a portion of fluid is not going in and out the pump or similar problems. Or decresing  the internal time steps of the tank.

I tried a wide rate of values for both variables  but it didn´t work. And that happens just not always in the same time step, it depends on the limit of my simulation, i find that strange as well. 

So i´m getting into the "physics behind" during the weekend, but ...hat anyone any advice?

 

And, about the same situation , with water in der solar loop everything runs with no problems...but can someone explains to me how  deals TRNSYS with a freezed fluid in the collector?

 

Thanks a lot!!! Enjoy the weekend

(David, thank you, I added my new type succesfully after testing)

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