Re: [TRNSYS-users] The necessity of using pipes in TRNSYS models

[Ben Heymer <bheymer@gmail.com>]

Amir,

Yes, you should include pipes in the loop with at least enough volume
to handle the flow during one timestep. If you think this volume is
unrealistically high, reduce your time step. You can set the thermal
losses of the pipes to zero if you choose.

I sometimes use an equation to define the minimum pipe length to avoid
convergence errors as I explore a model. If you define your time step
as a global parameter, you can use something like:

minpipelength = 1.1 * pipeflow (m^3/hr) * timestep (hr) / pipearea (m2)
pipelength = max(minpipelength, realpipelength)

-Ben Heymer

On Tue, Jun 24, 2014 at 8:50 AM, Amir Nashed <nashed.amir@gmail.com> wrote:
> Dear TRNSYS users
>
> I am currently trying to model an application using solar collectors to heat
> water and i realized that when i put pipes in the solar collector loop, i
> get strange output water temperatures (very low values).
>
> So what i did is that i isolated the solar collector loop and modeled it by
> itself and the same problem occurs unless i use very small pipes in terms of
> size.
>
> But if i used a small pipe size i sometimes get the warning that the flow
> rate the pipe during at least one component was greater than the capacity of
> the pipe.
>
> has anyone faced trouble with the pipes before? And is using pipes in the
> model needed from the first place in terms of the model stability?
>
> Thank you
>
>
>
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