[TRNSYS-users] Calling a component within a TRNSYS Iteration

[David BRADLEY]

Aaron,
There are two TRNSYS components that do something similar to what you 
are proposing. Type45 (a thermosiphon solar collector) calls Type38 (a 
liquid storage tank) internally. There aren't any iterations between the 
two components in this case, the TRNSYS kernel passes input information 
to Type45, Type45 calls Type38 to solve the thermal storage part, Type38 
returns its results to Type45 and then Type45 returns both its results 
and Type38's results to the TRNSYS kernel. You may be able to use the 
Type45 and type38 code to work out the mechanics of how your two Types 
are going to pass information back and forth.

The next thing you will need to do is to write your own iterative solver 
within one of your two Types. Your solver will pass Type A's results to 
Type B, get Type B's results and resolve Type A, continuing until it 
decides that the results match. There are a number of TRNSYS components 
that have internal iterative solvers. Type508 in the TESS Libraries is a 
good example. Type60 in the standard library has an internal solver as 
well but its code is, shall we say, not the easiest to follow.

My concern about your proposed method is that the TRNSYS kernel calls 
all Types, passes them their input information, recuperates their output 
information, and uses that output information to determine convergence 
of the system. In your case, the kernel is going to call both Type A and 
Type B and not be aware that they are communicating directly between 
themselves. The kernel will call Type A, which comes to a converged 
solution internally with Type B, then call Type B and ... I'm not sure 
whether you want B to call A and do something. Is there some reason why 
"B" is a Type? Can it be a subroutine of Type A? If it has inputs of its 
own that interact with other components in the system, those inputs can 
all be passed to it through Type A's input list. I think that your 
problem will be much easier to solve if you are able to redefine Type B 
as a subroutine of Type A.
regards,
David



On 10/4/2011 19:06, Aaron J. Danenberg wrote:
> TRNSYS Users:
>
> I have a simulation consisting of 5 or more components.  Two
> of which require an "iteration within an iteration".  This
> means that two of the components in the system must feed
> each other outputs and inputs within a single iteration
> before the TRNSYS solver takes over.  Both components are
> user written, without going into further explanation they
> cannot be combined into a single component.  I am trying to
> figure out how within a loop in my code I can call the other
> single component strictly within that specific loop.  In
> this loop I want only these two components in this system
> passing inputs an outputs back and forth until the criteria
> is is satisfied.  In my problem we can call the variable X,
> both components have different methods in which they compute
> X, and each of the components require the output from the
> other component to calculate their respective X.  The TRNSYS
> solver is not appropriate for the iterative scheme that must
> be used between these two components, so I need to figure
> out a way to run an iteration between two components within
> each TRNSYS iteration.  It may be possible for me to modify
> the control of the TRNSYS solver, but I am not where to even
> begin.  Thanks for reading my question!
>
> -Aaron
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>
>

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David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
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