Adding a new fluid

[theo-bech]

Hi all,

I'm new to TESpy and I've been researching how I can add a fluid that's not part of the existing catalogue for my simulation. Can I manually input the fluid properties vs. temperature somewhere? I read in a previous discussion that this might not be possible, but I wasn't entirely sure the issue was the same, as additional properties seemed to be the focus.

Thank you!

[fwitte]

Dear @theo-bech,

TL;DR: There are very limited and rather hacky options at the moment.

• With the current architecture you basically have to create some custom functions and replace inbuilt functions in you localy copy of TESPy to do that. I did that for some polynomes to validate a model on this branch: https://github.com/oemof/tespy/tree/features/KKH_combustion_validation/src/tespy/tools. You can have a look at kkh.py and the respective implementation in the fluid_properties.py module. However it is not really stable and mostly untested, the only use case is this one: https://github.com/KarimHShawky/Chemical-Exergy-in-TESPy. If you have some time this might be a possiblilty.
• Another option would be to work on the new design for a new fluid property back end I had started to work with a couple months ago. This would make it easy to include custom fluid property functions https://github.com/oemof/tespy/tree/features/flexible-fluid-property-back-end/fluid_properties, but did not have the time to finish that. It needs quite some work for implementing the new design in the software. If you are willing to input some more time on this, we could have some discussion about how the solution should look like and how to implement it.
• Last option is to build own CoolProp fluids, there are some information on how to do that on their website, also maybe consider this issue Adding New Fluids - all_incompressibles.py CoolProp/CoolProp#1931. I have never done something like this, so I would not really be of help here.

Best

Francesco

[fwitte]

Thanks very much. Sorry to insist, but how is the -3.27e+02 derived then? I'm playing with 1176 and 327 and can't connect them via the mass flow (m=1)!

I struggle to understand, what you want to say here. For the lowest temperature value I do get the correct results, I do not see where the 327 comes from, what are your inputs for that result?

[Jesus-Fuentes]

from tespy.networks import Network
from tespy.connections import Connection
from tespy.components import Source
from tespy.components import Sink
from tespy.components import HeatExchangerSimple


# define cycle
cycle = Network(fluids=['air', 'water'])
cycle.set_attr(p_unit='bar', T_unit='C', v_unit='m3 / h', h_unit='kJ / kg',
               m_unit='kg / h')
cycle.set_attr(iterinfo=False)

# define components
inlet = Source('Inlet')
HE = HeatExchangerSimple('HE')
outlet = Sink('Outlet')

# define connections
conn1 = Connection(inlet, 'out1', HE, 'in1')
conn2 = Connection(HE, 'out1', outlet, 'in1')

conn1.set_attr(p=2, T=170, m=1, fluid={'water': 0.5, 'air': 0.5})
conn2.set_attr(T=110)

cycle.add_conns(conn1, conn2)

HE.set_attr(pr=0.99)
# %% key parameter
HE.set_attr()

cycle.solve('design')
cycle.print_results()

for T in range(70, 110)[::-1]:
    conn2.set_attr(T=T)

    cycle.solve('design')
    cycle.print_results()

That's the code I've run. And the final output comes out as this:

##### RESULTS (HeatExchangerSimple) #####
+----+-----------+----------+----------+-----+-----+------+------+--------+
|    |         Q |       pr |     zeta |   D |   L |   ks |   kA |   Tamb |
|----+-----------+----------+----------+-----+-----+------+------+--------|
| HE | -3.27e+02 | 9.90e-01 | 7.73e+10 | nan | nan |  nan |  nan |    nan |
+----+-----------+----------+----------+-----+-----+------+------+--------+
##### RESULTS (Connection) #####
+--------------------+-----------+-----------+-----------+-----------+
|                    |         m |         p |         h |         T |
|--------------------+-----------+-----------+-----------+-----------|
| Inlet:out1_HE:in1  | 1.000e+00 | 2.000e+00 | 1.693e+03 | 1.700e+02 |
| HE:out1_Outlet:in1 | 1.000e+00 | 1.980e+00 | 5.171e+02 | 7.000e+01 |
+--------------------+-----------+-----------+-----------+-----------+

[Jesus-Fuentes]

See the Q -3.27e+02 ?

[fwitte]

It is because you have the mass flow unit kg / h. So 1 kg / h * 1 h / 3600 s * 1176 kJ / kg = 0.0327 kW or 327 W.

[Jesus-Fuentes]

Ahh! I had 1176/327 = 3.596 but the penny didn't drop!
Thanks. One last question, please. The code so far has no way of showing the mass of water that has condensed?

I've tried having a peek at this:

dir(conn2)

but I haven't found anything. This gives you the composition indeed, but no further info on water state:

conn2.fluid.val
OrderedDict([('air', 0.49999999999999994), ('water', 0.49999999999999994)])

[fwitte]

@theo-bech: If still relevant, the new version of tespy opens its API to implement user specified fluids, see https://tespy.readthedocs.io/en/main/modules/fluid_properties.html#tespy-fluid-properties-label and https://github.com/oemof/tespy/tree/dev/src/tespy/tools/fluid_properties