Small error in BoilerTurbogenerator design cause negative work/cost

[yalinli2]

@emilypl2 and I ran into a problem when running the lactic acid module with biosteam's BoilerTurbogenerator. Essentially a very small negative value (to 10^-15) was calculated for H_electricity:

biosteam/biosteam/facilities/_boiler_turbogenerator.py

Line 334 in e2db475

H_electricity = H_content - H_steam

which led to negative work and error in decorated cost calculation:

biosteam/biosteam/units/decorators/_cost.py

Line 152 in e2db475

C[i] = I * (x.f(F) if x.f else x.cost * F**x.n)

I locally inserted a line H_electricity = 0 if abs(H_electricity)<1e-6 else H_electricity to temporarily fix it for now, but not sure if it's good for a permanent fix, thanks!

[yoelcortes]

@yalinli2,

The temporary fix confuses the solver. I added some code to handle this special case. I am not able to test it, but I believe it should fix your issue:

biosteam/biosteam/facilities/_boiler_turbogenerator.py

Line 355 in a00a856

if self.cooling_duty > 0.:

Thanks,

[yalinli2]

lol I know my two-second fix would be problematic, I think your fix works, thank you!

@emilypl2 I didn't test all the way through, feel free to reopen this issue and follow up if you run into future problems!