Generalised offdesign parametrization

[bilwint]

11

• Created a Generalized off-design parametrization.

Todo

• Generalise simulation part (additional function for those models with intermediate states.)

[jfreissmann]

Hey @bilwint,

thank you for your work. I think, you found an elegant way to generalize the components offdesign parametrization. In my opinion, your PR looks mostly great. Some smaller remarks before we can merge:

• If I am not mistaken, the HeatPumpEconIHX class still implements the offdesign_simulation method. Is this necessary for some reason or was it an oversight?
• As we always set the massflow in partload operation in the 'A'-cycle, it is not strictly necessary to also save the design massflow of the 'D'-cycle in multicyclic heat pumps. On the other hand, it is no problem to save them anyways.
• The HeatPumpEcon, HeatPumpSimpleTrans and HeatPumpSimple classes reimplement the intermediate_states_offdesign method only for it to pass, which is not needed, as it is already inherited that way
• Just for my understanding: The get_pressure_levels methods of transcritical heat pumps had to be adjusted for them to work with offdesign simulation?

As far as I can tell, if you could refer to the points above and clear those up, there is nothing else in the way towards merging your PR.

Best regards.

[bilwint]

Hey @jfreissmann

1. offdesign_simulation for the case of HeatPumpEconIHX, is just a mistake
2. Regarding mass flow rate, you are right. Always sets the mass flow rate of cycle A in off-design. I did it because to make the code clear when it comes to the cascade cycle.
3. Third point also you are right.
4. For transcritical model, the pressure in the transcritical heat exchanger will remain same but the evaporator pressure will change when there is variation in the source temperature, am I right ?.

[jfreissmann]

I agree with your second point. The advantage of the previous implementation was, that every heat pump class has the same attribute, that contains the design mass flow in the 'A'-cycle and only that. But this uniformity is broken with things like self.wf vs. self.wf1 + self.wf2 etc. anyway, so maybe it is non really needed.

Regarding the changes of some of the get_pressure_levels method: we use it mostly to get good starting values for the initial design simulation or for calculating the correct intermediate pressure. The former usage sould not affect the offdesign simulation, but for the latter case it makes sense, that changing the source temperature from outside the get_pressure_levels method should result in a differrent intermediate pressure. I am not 100% sure, if we correctly do that right now in all models depending on an intermediate pressure though.

[bilwint]

Sorry I misunderstood the fourth question regarding the get_pressure_levels for trans models.

The get_pressure_levels function had to adjust to implement generalized off-design. Because in the previous case there was no arguments in get_pressure_levels(self, wf=None). So it was not convenient to find intermediate states (p/T). That's why I implemented arguments to the get_pressure_levels(self, T_evap, wf=None) of trans models.

Is that was your question?

[jfreissmann]

Yes, that does answer my question. When you adjust the other open points from my initial comment, we can merge the PR.