[TRNSYS-users] Calculating properties for ethylene glycol water

[Mukhtar Abeid]

Dear Josè

There is a data and chart in ASHAE Fundamentals where they might be modeled
in 1-D lookup table.
Whereas, there is a type in TRNSYS that works like the look up table.

I hope that helps you.
Thanks


في الاثنين، ٢١ يونيو ٢٠٢١ ١٩:٢٩ Jeff Thornton via TRNSYS-users <
trnsys-users at lists.onebuilding.org> كتب:

> José,
>
> Before you decide to code your own model to calculate the properties for
> Ethylene Glycol I want to remind you of a few things that many users
> forget.  If you use variable fluid properties then every model that that
> fluid flows into will need to be re-coded; pipes, tanks, valves etc.
> Otherwise you will run into major energy balance issues in your system.
> And it’s not simply just moving the properties in those models from
> parameters to inputs - it’s the fundamental governing differential
> equations for the models that also change. With density now a function of
> temperature, the mass of the fluid changes in a pipe or tank forca given
> volume - which means you have to re-derive the entire solution.  And beyond
> that you have to now code special controllers to move the fluid.  Imagine a
> case where a tank of water is just sitting there and slowly losing energy
> to the environment.  Usually that’s a pretty simple case to solve.  But now
> as the fluid cools, the density increases and the mass in the tank now
> takes up less volume - so water will enter the tank to take up the newly
> freed volume.  Is this water coming from the pipe leading to the tank, the
> pipe leaving the tank?  In most systems it comes from an expansion tank and
> flows into the tank from either, or possibly even both, pipes...
>
> At TESS, we have a series of models that incorporate the change in fluid
> properties with temperature as part of our high temperature solar library.
> But long before you decide to go down the variable property route you
> should ask yourself if the small change in fluid property accuracy is worth
> the major changes you’ll need to make.
>
> Run a simulation with constant “cold” fluid properties and then one with
> constant “hot” properties.  How different are the results - likely not very
> different at all.
>
> Jeff
>
> Sent from my iPhone
>
> On Jun 21, 2021, at 6:19 AM, RUBIO RUBIO, JOSÉ JAVIER via TRNSYS-users <
> trnsys-users at lists.onebuilding.org> wrote:
>
> 
>
> Dear TRNSYS users,
>
>
>
> Anyone knows some way for calculating the properties of the ethylene
> glycol water (density, specific heat and thermal conductivity) by using the
> temperature as an input? I have thought in creating a new type in
> Simulation Studio to code it in FORTRAN, which would call REFPROP to
> calculate the properties (although REFPROP doesn’t have ethylene glycol
> water in its database), but I don’t really know how to do it properly.
>
>
>
> Thanks in advance.
>
>
>
> Regards.
>
>
>
> Jose Javier.
>
>
>
>
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